1
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Biswas S, Gurdziel K, Meller VH. siRNA that participates in Drosophila dosage compensation is produced by many 1.688X and 359 bp repeats. Genetics 2024; 227:iyae074. [PMID: 38718207 PMCID: PMC11228850 DOI: 10.1093/genetics/iyae074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Accepted: 04/29/2024] [Indexed: 07/09/2024] Open
Abstract
Organisms with differentiated sex chromosomes must accommodate unequal gene dosage in males and females. Male fruit flies increase X-linked gene expression to compensate for hemizygosity of their single X chromosome. Full compensation requires localization of the Male-Specific Lethal (MSL) complex to active genes on the male X, where it modulates chromatin to elevate expression. The mechanisms that identify X chromatin are poorly understood. The euchromatic X is enriched for AT-rich, ∼359 bp satellites termed the 1.688X repeats. Autosomal insertions of 1.688X DNA enable MSL recruitment to nearby genes. Ectopic expression of dsRNA from one of these repeats produces siRNA and partially restores X-localization of MSLs in males with defective X recognition. Surprisingly, expression of double-stranded RNA from three other 1.688X repeats failed to rescue males. We reconstructed dsRNA-expressing transgenes with sequence from two of these repeats and identified phasing of repeat DNA, rather than sequence or orientation, as the factor that determines rescue of males with defective X recognition. Small RNA sequencing revealed that siRNA was produced in flies with a transgene that rescues, but not in those carrying a transgene with the same repeat but different phasing. We demonstrate that pericentromeric X heterochromatin promotes X recognition through a maternal effect, potentially mediated by small RNA from closely related heterochromatic repeats. This suggests that the sources of siRNAs promoting X recognition are highly redundant. We propose that enrichment of satellite repeats on Drosophilid X chromosomes facilitates the rapid evolution of differentiated sex chromosomes by marking the X for compensation.
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Affiliation(s)
- Sudeshna Biswas
- Department of Biological Sciences, Wayne State University, 5047 Gullen Mall, Detroit, MI 48202, USA
| | - Katherine Gurdziel
- Department of Pharmacology, Wayne State University, Integrative Bioscience Center (iBio), 6135 Woodward, Detroit, MI 48202, USA
- Institute of Environmental Health Sciences, Wayne State University, Integrative Bioscience Center (iBio), 6135 Woodward, Detroit, MI 48202, USA
| | - Victoria H Meller
- Department of Biological Sciences, Wayne State University, 5047 Gullen Mall, Detroit, MI 48202, USA
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2
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Atinbayeva N, Valent I, Zenk F, Loeser E, Rauer M, Herur S, Quarato P, Pyrowolakis G, Gomez-Auli A, Mittler G, Cecere G, Erhardt S, Tiana G, Zhan Y, Iovino N. Inheritance of H3K9 methylation regulates genome architecture in Drosophila early embryos. EMBO J 2024; 43:2685-2714. [PMID: 38831123 PMCID: PMC11217351 DOI: 10.1038/s44318-024-00127-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Revised: 03/27/2024] [Accepted: 04/15/2024] [Indexed: 06/05/2024] Open
Abstract
Constitutive heterochromatin is essential for transcriptional silencing and genome integrity. The establishment of constitutive heterochromatin in early embryos and its role in early fruitfly development are unknown. Lysine 9 trimethylation of histone H3 (H3K9me3) and recruitment of its epigenetic reader, heterochromatin protein 1a (HP1a), are hallmarks of constitutive heterochromatin. Here, we show that H3K9me3 is transmitted from the maternal germline to the next generation. Maternally inherited H3K9me3, and the histone methyltransferases (HMT) depositing it, are required for the organization of constitutive heterochromatin: early embryos lacking H3K9 methylation display de-condensation of pericentromeric regions, centromere-centromere de-clustering, mitotic defects, and nuclear shape irregularities, resulting in embryo lethality. Unexpectedly, quantitative CUT&Tag and 4D microscopy measurements of HP1a coupled with biophysical modeling revealed that H3K9me2/3 is largely dispensable for HP1a recruitment. Instead, the main function of H3K9me2/3 at this developmental stage is to drive HP1a clustering and subsequent heterochromatin compaction. Our results show that HP1a binding to constitutive heterochromatin in the absence of H3K9me2/3 is not sufficient to promote proper embryo development and heterochromatin formation. The loss of H3K9 HMTs and H3K9 methylation alters genome organization and hinders embryonic development.
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Affiliation(s)
- Nazerke Atinbayeva
- Max Planck Institute of Immunobiology and Epigenetics, 79108, Freiburg im Breisgau, Germany
- Albert-Ludwigs-Universität Freiburg, Fahnenbergplatz, 79085, Freiburg im Breisgau, Germany
| | - Iris Valent
- Karlsruhe Institute of Technology (KIT), Zoological Institute, 76131, Karlsruhe, Germany
| | - Fides Zenk
- Brain Mind Institute, School of Life Sciences EPFL, SV3809, 1015, Lausanne, Switzerland
| | - Eva Loeser
- Max Planck Institute of Immunobiology and Epigenetics, 79108, Freiburg im Breisgau, Germany
| | - Michael Rauer
- Max Planck Institute of Immunobiology and Epigenetics, 79108, Freiburg im Breisgau, Germany
| | - Shwetha Herur
- Max Planck Institute of Immunobiology and Epigenetics, 79108, Freiburg im Breisgau, Germany
| | - Piergiuseppe Quarato
- San Raffaele Telethon Institute for Gene Therapy, IRCCS San Raffaele Scientific Institute, 20132, Milan, Italy
| | - Giorgos Pyrowolakis
- Centre for Biological signaling studies, University of Freiburg, 79104, Freiburg im Breisgau, Germany
| | - Alejandro Gomez-Auli
- Max Planck Institute of Immunobiology and Epigenetics, 79108, Freiburg im Breisgau, Germany
| | - Gerhard Mittler
- Max Planck Institute of Immunobiology and Epigenetics, 79108, Freiburg im Breisgau, Germany
| | - Germano Cecere
- Institute Pasteur, Mechanisms of Epigenetic Inheritance, Department of Developmental and Stem Cell Biology, UMR3738, CNRS, 75724, Cedex 15, Paris, France
| | - Sylvia Erhardt
- Karlsruhe Institute of Technology (KIT), Zoological Institute, 76131, Karlsruhe, Germany
| | - Guido Tiana
- Università degli Studi di Milano and INFN, Milan, Italy
| | - Yinxiu Zhan
- Department of Experimental Oncology, European Institute of Oncology-IRCCS, Milan, Italy.
| | - Nicola Iovino
- Max Planck Institute of Immunobiology and Epigenetics, 79108, Freiburg im Breisgau, Germany.
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3
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Fukushima HS, Ikeda T, Ikeda S, Takeda H. Cell cycle length governs heterochromatin reprogramming during early development in non-mammalian vertebrates. EMBO Rep 2024:10.1038/s44319-024-00188-5. [PMID: 38943003 DOI: 10.1038/s44319-024-00188-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2024] [Revised: 06/06/2024] [Accepted: 06/12/2024] [Indexed: 06/30/2024] Open
Abstract
Heterochromatin marks such as H3K9me3 undergo global erasure and re-establishment after fertilization, and the proper reprogramming of H3K9me3 is essential for early development. Despite the widely conserved dynamics of heterochromatin reprogramming in invertebrates and non-mammalian vertebrates, previous studies have shown that the underlying mechanisms may differ between species. Here, we investigate the molecular mechanism of H3K9me3 dynamics in medaka (Japanese killifish, Oryzias latipes) as a non-mammalian vertebrate model, and show that rapid cell cycle during cleavage stages causes DNA replication-dependent passive erasure of H3K9me3. We also find that cell cycle slowing, toward the mid-blastula transition, permits increasing nuclear accumulation of H3K9me3 histone methyltransferase Setdb1, leading to the onset of H3K9me3 re-accumulation. We further demonstrate that cell cycle length in early development also governs H3K9me3 reprogramming in zebrafish and Xenopus laevis. Together with the previous studies in invertebrates, we propose that a cell cycle length-dependent mechanism for both global erasure and re-accumulation of H3K9me3 is conserved among rapid-cleavage species of non-mammalian vertebrates and invertebrates such as Drosophila, C. elegans, Xenopus and teleost fish.
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Affiliation(s)
- Hiroto S Fukushima
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, 113-0033, Japan.
- Center for Integrative Medical Sciences, RIKEN, Yokohama, 230-0045, Japan.
| | - Takafumi Ikeda
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, 113-0033, Japan
- Institute for Protein Dynamics, Kyoto Sangyo University, Kyoto, 603-8555, Japan
- Faculty of Life Sciences, Kyoto Sangyo University, Kyoto, 603-8555, Japan
| | - Shinra Ikeda
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, 113-0033, Japan
| | - Hiroyuki Takeda
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, 113-0033, Japan.
- Faculty of Life Sciences, Kyoto Sangyo University, Kyoto, 603-8555, Japan.
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4
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Stutzman AV, Hill CA, Armstrong RL, Gohil R, Duronio RJ, Dowen JM, McKay DJ. Heterochromatic 3D genome organization is directed by HP1a- and H3K9-dependent and independent mechanisms. Mol Cell 2024; 84:2017-2035.e6. [PMID: 38795706 PMCID: PMC11185254 DOI: 10.1016/j.molcel.2024.05.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 03/07/2024] [Accepted: 05/02/2024] [Indexed: 05/28/2024]
Abstract
Whether and how histone post-translational modifications and the proteins that bind them drive 3D genome organization remains unanswered. Here, we evaluate the contribution of H3K9-methylated constitutive heterochromatin to 3D genome organization in Drosophila tissues. We find that the predominant organizational feature of wild-type tissues is the segregation of euchromatic chromosome arms from heterochromatic pericentromeres. Reciprocal perturbation of HP1a⋅H3K9me binding, using a point mutation in the HP1a chromodomain or replacement of the replication-dependent histone H3 with H3K9R mutant histones, revealed that HP1a binding to methylated H3K9 in constitutive heterochromatin is required to limit contact frequency between pericentromeres and chromosome arms and regulate the distance between arm and pericentromeric regions. Surprisingly, the self-association of pericentromeric regions is largely preserved despite the loss of H3K9 methylation and HP1a occupancy. Thus, the HP1a⋅H3K9 interaction contributes to but does not solely drive the segregation of euchromatin and heterochromatin inside the nucleus.
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Affiliation(s)
- Alexis V Stutzman
- Curriculum in Genetics & Molecular Biology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Christina A Hill
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Robin L Armstrong
- Curriculum in Genetics & Molecular Biology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Riya Gohil
- Curriculum in Genetics & Molecular Biology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Robert J Duronio
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC 27599, USA; Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA; Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA; Department of Genetics, University of North Carolina, Chapel Hill, NC 27599, USA.
| | - Jill M Dowen
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC 27599, USA; Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA; Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA; Department of Biochemistry & Biophysics, University of North Carolina, Chapel Hill, NC 27599, USA.
| | - Daniel J McKay
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC 27599, USA; Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA; Department of Genetics, University of North Carolina, Chapel Hill, NC 27599, USA.
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5
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Brockett JS, Manalo T, Zein-Sabatto H, Lee J, Fang J, Chu P, Feng H, Patil D, Davidson P, Ogan K, Master VA, Pattaras JG, Roberts DL, Bergquist SH, Reyna MA, Petros JA, Lerit DA, Arnold RS. A missense SNP in the tumor suppressor SETD2 reduces H3K36me3 and mitotic spindle integrity in Drosophila. Genetics 2024; 226:iyae015. [PMID: 38290049 PMCID: PMC10990431 DOI: 10.1093/genetics/iyae015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Revised: 01/11/2024] [Accepted: 01/11/2024] [Indexed: 02/01/2024] Open
Abstract
Mutations in SETD2 are among the most prevalent drivers of renal cell carcinoma (RCC). We identified a novel single nucleotide polymorphism (SNP) in SETD2, E902Q, within a subset of RCC patients, which manifests as both an inherited or tumor-associated somatic mutation. To determine if the SNP is biologically functional, we used CRISPR-based genome editing to generate the orthologous mutation within the Drosophila melanogaster Set2 gene. In Drosophila, the homologous amino acid substitution, E741Q, reduces H3K36me3 levels comparable to Set2 knockdown, and this loss is rescued by reintroduction of a wild-type Set2 transgene. We similarly uncovered significant defects in spindle morphogenesis, consistent with the established role of SETD2 in methylating α-Tubulin during mitosis to regulate microtubule dynamics and maintain genome stability. These data indicate the Set2 E741Q SNP affects both histone methylation and spindle integrity. Moreover, this work further suggests the SETD2 E902Q SNP may hold clinical relevance.
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Affiliation(s)
- Jovan S Brockett
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Tad Manalo
- Department of Urology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Hala Zein-Sabatto
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Jina Lee
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Junnan Fang
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Philip Chu
- Department of Urology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Harry Feng
- Department of Urology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Dattatraya Patil
- Department of Urology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Priscilla Davidson
- Department of Urology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Kenneth Ogan
- Department of Urology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Viraj A Master
- Department of Urology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - John G Pattaras
- Department of Urology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - David L Roberts
- Emory University Department of Medicine, Division of General Internal Medicine, Atlanta, GA 30322, USA
| | - Sharon H Bergquist
- Emory University Department of Medicine, Division of General Internal Medicine, Atlanta, GA 30322, USA
| | - Matthew A Reyna
- Department of Biomedical Informatics, Emory University School of Medicine, Atlanta, GA 30322, USA
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - John A Petros
- Department of Urology, Emory University School of Medicine, Atlanta, GA 30322, USA
- Winship Cancer Institute, Emory University, Atlanta, GA 30322, USA
| | - Dorothy A Lerit
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
- Winship Cancer Institute, Emory University, Atlanta, GA 30322, USA
| | - Rebecca S Arnold
- Department of Urology, Emory University School of Medicine, Atlanta, GA 30322, USA
- Winship Cancer Institute, Emory University, Atlanta, GA 30322, USA
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6
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Lu T, Yang J, Cai Y, Ding M, Yu Z, Fang X, Zhou X, Wang X. NCAPD3 promotes diffuse large B-cell lymphoma progression through modulating SIRT1 expression in an H3K9 monomethylation-dependent manner. J Adv Res 2024:S2090-1232(24)00086-9. [PMID: 38432395 DOI: 10.1016/j.jare.2024.02.024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Revised: 01/31/2024] [Accepted: 02/29/2024] [Indexed: 03/05/2024] Open
Abstract
INTRODUCTION Condensin, a family of structural maintenance of chromosome complexes, has been shown to regulate chromosome compaction and segregation during mitosis. NCAPD3, a HEAT-repeat subunit of condensin II, plays a dominant role in condensin-mediated chromosome dynamics but remains unexplored in lymphoma. OBJECTIVES The study aims to unravel the molecular function and mechanism of NCAPD3 in diffuse large B-cell lymphoma (DLBCL). METHODS The expression and clinical significance of NCAPD3 were assessed in public database and clinical specimens. Chromosome spreads, co-immunoprecipitation (co-IP), mass spectrometry (MS), and chromatin immunoprecipitation (ChIP) assays were conducted to untangle the role and mechanism of NCAPD3 in DLBCL. RESULTS NCAPD3 was highly expressed in DLBCL, correlated with poor prognosis. NCAPD3 deficiency impeded cell proliferation, induced apoptosis and increased the chemosensitivity. Instead, NCAPD3 overexpression facilitated cell proliferation. In vivo experiments further indicated targeting NCAPD3 suppressed tumor growth. Noteworthily, NCAPD3 deficiency disturbed the mitosis, triggering the formation of aneuploids. To reveal the function of NCAPD3 in DLBCL, chromosome spreads were conducted, presenting that chromosomes became compact upon NCAPD3 overexpression, instead, loose, twisted and lacking axial rigidity upon NCAPD3 absence. Meanwhile, the classical transcription-activated marker, H3K4 trimethylation, was found globally upregulated after NCAPD3 knockout, suggesting that NCAPD3 might participate in chromatin remodeling and transcription regulation. MS revealed NCAPD3 could interact with transcription factor, TFII I. Further co-IP and ChIP assays verified NCAPD3 could be anchored at the promoter of SIRT1 by TFII I and then supported the transcription of SIRT1 via recognizing H3K9 monomethylation (H3K9me1) on SIRT1 promoter. Function reversion assay verified the oncogenic role of NCAPD3 in DLBCL was partially mediated by SIRT1. CONCLUSION This study demonstrated that dysregulation of NCAPD3 could disturb chromosome compaction and segregation and regulate the transcription activity of SIRT1 in an H3K9me1-dependent manner, which provided novel insights into targeted strategy for DLBCL.
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Affiliation(s)
- Tiange Lu
- Department of Hematology, Shandong Provincial Hospital, Shandong University, Jinan, Shandong 250021, China
| | - Juan Yang
- Department of Hematology, Shandong Provincial Hospital, Shandong University, Jinan, Shandong 250021, China; National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, China
| | - Yiqing Cai
- Department of Hematology, Shandong Provincial Hospital, Shandong University, Jinan, Shandong 250021, China
| | - Mengfei Ding
- Department of Hematology, Shandong Provincial Hospital, Shandong University, Jinan, Shandong 250021, China
| | - Zhuoya Yu
- Department of Hematology, Shandong Provincial Hospital, Shandong University, Jinan, Shandong 250021, China
| | - Xiaosheng Fang
- Department of Hematology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong 250021, China; Taishan Scholars Program of Shandong Province, Jinan, Shandong 250021, China; Branch of National Clinical Research Center for Hematologic Diseases, Jinan, Shandong 250021, China; National Clinical Research Center for Hematologic Diseases, the First Affiliated Hospital of Soochow University, Suzhou 251006, China.
| | - Xiangxiang Zhou
- Department of Hematology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong 250021, China; Taishan Scholars Program of Shandong Province, Jinan, Shandong 250021, China; Branch of National Clinical Research Center for Hematologic Diseases, Jinan, Shandong 250021, China; National Clinical Research Center for Hematologic Diseases, the First Affiliated Hospital of Soochow University, Suzhou 251006, China.
| | - Xin Wang
- Department of Hematology, Shandong Provincial Hospital, Shandong University, Jinan, Shandong 250021, China; Department of Hematology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong 250021, China; Taishan Scholars Program of Shandong Province, Jinan, Shandong 250021, China; Branch of National Clinical Research Center for Hematologic Diseases, Jinan, Shandong 250021, China; National Clinical Research Center for Hematologic Diseases, the First Affiliated Hospital of Soochow University, Suzhou 251006, China.
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7
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Zhang Y, Yu H, Wang D, Lei X, Meng Y, Zhang N, Chen F, Lv L, Pan Q, Qin H, Zhang Z, van Aalten DMF, Yuan K. Protein O-GlcNAcylation homeostasis regulates facultative heterochromatin to fine-tune sog-Dpp signaling during Drosophila early embryogenesis. J Genet Genomics 2023; 50:948-959. [PMID: 37286164 DOI: 10.1016/j.jgg.2023.05.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2022] [Revised: 04/30/2023] [Accepted: 05/18/2023] [Indexed: 06/09/2023]
Abstract
Protein O-GlcNAcylation is a monosaccharide post-translational modification maintained by two evolutionarily conserved enzymes, O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). Mutations in human OGT have recently been associated with neurodevelopmental disorders, although the mechanisms linking O-GlcNAc homeostasis to neurodevelopment are not understood. Here, we investigate the effects of perturbing protein O-GlcNAcylation using transgenic Drosophila lines that overexpress a highly active OGA. We reveal that temporal reduction of protein O-GlcNAcylation in early embryos leads to reduced brain size and olfactory learning in adult Drosophila. Downregulation of O-GlcNAcylation induced by the exogenous OGA activity promotes nuclear foci formation of Polycomb-group protein Polyhomeotic and the accumulation of excess K27 trimethylation of histone H3 (H3K27me3) at the mid-blastula transition. These changes interfere with the zygotic expression of several neurodevelopmental genes, particularly shortgastrulation (sog), a component of an evolutionarily conserved sog-Decapentaplegic (Dpp) signaling system required for neuroectoderm specification. Our findings highlight the importance of early embryonic O-GlcNAcylation homeostasis for the fidelity of facultative heterochromatin redeployment and initial cell fate commitment of neuronal lineages, suggesting a possible mechanism underpinning OGT-associated intellectual disability.
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Affiliation(s)
- Yaowen Zhang
- Center for Medical Genetics, School of Life Sciences & Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Haibin Yu
- Center for Medical Genetics, School of Life Sciences & Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Dandan Wang
- Center for Medical Genetics, School of Life Sciences & Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Xiaoyun Lei
- Center for Medical Genetics, School of Life Sciences & Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Yang Meng
- Center for Medical Genetics, School of Life Sciences & Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Na Zhang
- Center for Medical Genetics, School of Life Sciences & Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Fang Chen
- Center for Medical Genetics, School of Life Sciences & Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Lu Lv
- Center for Medical Genetics, School of Life Sciences & Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Qian Pan
- Center for Medical Genetics, School of Life Sciences & Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Hongtao Qin
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Biology, Hunan University, Changsha, Hunan 410082, China
| | - Zhuohua Zhang
- Center for Medical Genetics, School of Life Sciences & Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Daan M F van Aalten
- Center for Medical Genetics, School of Life Sciences & Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China; Division of Cell and Developmental Biology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, UK; Department of Molecular Biology and Genetics, University of Aarhus, Aarhus 8000, Denmark.
| | - Kai Yuan
- Center for Medical Genetics, School of Life Sciences & Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China; The Biobank of Xiangya Hospital, Central South University, Changsha, Hunan 410008, China.
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8
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Harrison MM, Marsh AJ, Rushlow CA. Setting the stage for development: the maternal-to-zygotic transition in Drosophila. Genetics 2023; 225:iyad142. [PMID: 37616526 PMCID: PMC10550319 DOI: 10.1093/genetics/iyad142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Accepted: 07/18/2023] [Indexed: 08/26/2023] Open
Abstract
The zygote has a daunting task ahead of itself; it must develop from a single cell (fertilized egg) into a fully functioning adult with a multitude of different cell types. In the beginning, the zygote has help from its mother, in the form of gene products deposited into the egg, but eventually, it must rely on its own resources to proceed through development. The transfer of developmental control from the mother to the embryo is called the maternal-to-zygotic transition (MZT). All animals undergo this transition, which is defined by two main processes-the degradation of maternal RNAs and the synthesis of new RNAs from the zygote's own genome. Here, we review the regulation of the MZT in Drosophila, but given the broad conservation of this essential process, much of the regulation is shared among metazoans.
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Affiliation(s)
- Melissa M Harrison
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI 53706USA
| | - Audrey J Marsh
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI 53706USA
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9
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Gaskill MM, Soluri IV, Branks AE, Boka AP, Stadler MR, Vietor K, Huang HYS, Gibson TJ, Mukherjee A, Mir M, Blythe SA, Harrison MM. Localization of the Drosophila pioneer factor GAF to subnuclear foci is driven by DNA binding and required to silence satellite repeat expression. Dev Cell 2023; 58:1610-1624.e8. [PMID: 37478844 PMCID: PMC10528433 DOI: 10.1016/j.devcel.2023.06.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 04/19/2023] [Accepted: 06/29/2023] [Indexed: 07/23/2023]
Abstract
The eukaryotic genome is organized to enable the precise regulation of gene expression. This organization is established as the embryo transitions from a fertilized gamete to a totipotent zygote. To understand the factors and processes that drive genomic organization, we focused on the pioneer factor GAGA factor (GAF) that is required for early development in Drosophila. GAF transcriptionally activates the zygotic genome and is localized to subnuclear foci. This non-uniform distribution is driven by binding to highly abundant GA repeats. At GA repeats, GAF is necessary to form heterochromatin and silence transcription. Thus, GAF is required to establish both active and silent regions. We propose that foci formation enables GAF to have opposing transcriptional roles within a single nucleus. Our data support a model in which the subnuclear concentration of transcription factors acts to organize the nucleus into functionally distinct domains essential for the robust regulation of gene expression.
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Affiliation(s)
- Marissa M Gaskill
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Isabella V Soluri
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
| | - Annemarie E Branks
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Alan P Boka
- Biochemistry and Molecular Biophysics Graduate Group, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA 19104, USA; Center for Computational and Genomic Medicine, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Michael R Stadler
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Katherine Vietor
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Hao-Yu S Huang
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Tyler J Gibson
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Apratim Mukherjee
- Center for Computational and Genomic Medicine, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA; Department of Cell and Developmental Biology, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Mustafa Mir
- Center for Computational and Genomic Medicine, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA; Epigenetics Institute, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA 19104, USA; Institute for Regenerative, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA 19104, USA; Department of Cell and Developmental Biology, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Shelby A Blythe
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
| | - Melissa M Harrison
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA.
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10
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Tortora MMC, Brennan LD, Karpen G, Jost D. HP1-driven phase separation recapitulates the thermodynamics and kinetics of heterochromatin condensate formation. Proc Natl Acad Sci U S A 2023; 120:e2211855120. [PMID: 37549295 PMCID: PMC10438847 DOI: 10.1073/pnas.2211855120] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 06/28/2023] [Indexed: 08/09/2023] Open
Abstract
The spatial segregation of pericentromeric heterochromatin (PCH) into distinct, membrane-less nuclear compartments involves the binding of Heterochromatin Protein 1 (HP1) to H3K9me2/3-rich genomic regions. While HP1 exhibits liquid-liquid phase separation properties in vitro, its mechanistic impact on the structure and dynamics of PCH condensate formation in vivo remains largely unresolved. Here, using a minimal theoretical framework, we systematically investigate the mutual coupling between self-interacting HP1-like molecules and the chromatin polymer. We reveal that the specific affinity of HP1 for H3K9me2/3 loci facilitates coacervation in nucleo and promotes the formation of stable PCH condensates at HP1 levels far below the concentration required to observe phase separation in purified protein assays in vitro. These heterotypic HP1-chromatin interactions give rise to a strong dependence of the nucleoplasmic HP1 density on HP1-H3K9me2/3 stoichiometry, consistent with the thermodynamics of multicomponent phase separation. The dynamical cross talk between HP1 and the viscoelastic chromatin scaffold also leads to anomalously slow equilibration kinetics, which strongly depend on the genomic distribution of H3K9me2/3 domains and result in the coexistence of multiple long-lived, microphase-separated PCH compartments. The morphology of these complex coacervates is further found to be governed by the dynamic establishment of the underlying H3K9me2/3 landscape, which may drive their increasingly abnormal, aspherical shapes during cell development. These findings compare favorably to 4D microscopy measurements of HP1 condensate formation in live Drosophila embryos and suggest a general quantitative model of PCH formation based on the interplay between HP1-based phase separation and chromatin polymer mechanics.
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Affiliation(s)
- Maxime M. C. Tortora
- Laboratoire de Biologie et Modélisation de la Cellule, École Normale Supérieure de Lyon, CNRS, UMR5239, Inserm U1293, Université Claude Bernard Lyon 1, 69007Lyon, France
| | - Lucy D. Brennan
- Department of Molecular and Cell Biology, University of California, Berkeley, CA94720
| | - Gary Karpen
- Department of Molecular and Cell Biology, University of California, Berkeley, CA94720
- Department of BioEngineering and BioMedical Sciences, Lawrence Berkeley National Laboratory, Berkeley, CA94720
| | - Daniel Jost
- Laboratoire de Biologie et Modélisation de la Cellule, École Normale Supérieure de Lyon, CNRS, UMR5239, Inserm U1293, Université Claude Bernard Lyon 1, 69007Lyon, France
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11
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Theis A, Harrison MM. Reprogramming of three-dimensional chromatin organization in the early embryo. Curr Opin Struct Biol 2023; 81:102613. [PMID: 37224641 PMCID: PMC10524315 DOI: 10.1016/j.sbi.2023.102613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Revised: 04/24/2023] [Accepted: 04/26/2023] [Indexed: 05/26/2023]
Abstract
Chromatin organization within the three-dimensional (3D) nuclear space is important for proper gene expression and developmental programming. This organization is established during the dramatic reprogramming that occurs in early embryonic development. Thus, the early embryo is an ideal model for examining the formation and dynamics of 3D chromatin structure. Advances in high-resolution microscopy and single-nucleus genomic analyses have provided fundamental insights into the mechanisms driving genome organization in the early embryo. Here, we highlight recent findings describing the dynamics and driving mechanisms for establishing 3D chromatin organization and discuss the role such organization has on gene regulation in early embryonic development.
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Affiliation(s)
- Alexandra Theis
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI, USA.
| | - Melissa M Harrison
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI, USA.
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12
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Abstract
The control of gene expression in eukaryotes relies on how transcription factors and RNA polymerases manipulate the structure of chromatin. These interactions are especially important in development as gene expression programs change. Chromatin generally limits the accessibility of DNA, and thus exposing sequences at regulatory elements is critical for gene expression. However, it is challenging to understand how transcription factors manipulate chromatin structure and the sequence of regulatory events. The Drosophila embryo has provided a powerful setting to directly observe the establishment and elaboration of chromatin features and experimentally test the causality of transcriptional events that are shared among many metazoans. The large embryo is tractable by live imaging, and a variety of well-developed tools allow the manipulation of factors during early development. The early embryo develops as a syncytium with rapid nuclear divisions and no zygotic transcription, with largely featureless chromatin. Thus, studies in this system have revealed the progression of genome activation triggered by pioneer factors that initiate DNA exposure at regulatory elements and the establishment of chromatin domains, including heterochromatin, the nucleolus, and nuclear bodies. The de novo emergence of nuclear structures in the early embryo reveals features of chromatin dynamics that are likely to be central to transcriptional regulation in all cells.
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Affiliation(s)
- Kami Ahmad
- Division of Basic Sciences, Fred Hutchinson Cancer Center, 1100 Fairview Ave. N., P.O. Box 19024, Seattle, WA 98109-1024, USA
| | - Steven Henikoff
- Division of Basic Sciences, Fred Hutchinson Cancer Center, 1100 Fairview Ave. N., P.O. Box 19024, Seattle, WA 98109-1024, USA
- Howard Hughes Medical Institute, 4000 Jones Bridge Road Chevy Chase, MD 20815-6789, USA
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13
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Cho CY, Seller CA, O’Farrell PH. Temporal control of late replication and coordination of origin firing by self-stabilizing Rif1-PP1 hubs in Drosophila. Proc Natl Acad Sci U S A 2022; 119:e2200780119. [PMID: 35733247 PMCID: PMC9245680 DOI: 10.1073/pnas.2200780119] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 05/19/2022] [Indexed: 12/25/2022] Open
Abstract
In the metazoan S phase, coordinated firing of clusters of origins replicates different parts of the genome in a temporal program. Despite advances, neither the mechanism controlling timing nor that coordinating firing of multiple origins is fully understood. Rif1, an evolutionarily conserved inhibitor of DNA replication, recruits protein phosphatase 1 (PP1) and counteracts firing of origins by S-phase kinases. During the midblastula transition (MBT) in Drosophila embryos, Rif1 forms subnuclear hubs at each of the large blocks of satellite sequences and delays their replication. Each Rif1 hub disperses abruptly just prior to the replication of the associated satellite sequences. Here, we show that the level of activity of the S-phase kinase, DDK, accelerated this dispersal program, and that the level of Rif1-recruited PP1 retarded it. Further, Rif1-recruited PP1 supported chromatin association of nearby Rif1. This influence of nearby Rif1 can create a "community effect" counteracting kinase-induced dissociation such that an entire hub of Rif1 undergoes switch-like dispersal at characteristic times that shift in response to the balance of Rif1-PP1 and DDK activities. We propose a model in which the spatiotemporal program of late replication in the MBT embryo is controlled by self-stabilizing Rif1-PP1 hubs, whose abrupt dispersal synchronizes firing of associated late origins.
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Affiliation(s)
- Chun-Yi Cho
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158
| | - Charles A. Seller
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158
| | - Patrick H. O’Farrell
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158
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14
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Yu C, Lei X, Chen F, Mao S, Lv L, Liu H, Hu X, Wang R, Shen L, Zhang N, Meng Y, Shen Y, Chen J, Li P, Huang S, Lin C, Zhang Z, Yuan K. ARID1A loss derepresses a group of human endogenous retrovirus-H loci to modulate BRD4-dependent transcription. Nat Commun 2022; 13:3501. [PMID: 35715442 PMCID: PMC9205910 DOI: 10.1038/s41467-022-31197-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 06/07/2022] [Indexed: 11/25/2022] Open
Abstract
Transposable elements (TEs) through evolutionary exaptation have become an integral part of the human genome, offering ample regulatory sequences and shaping chromatin 3D architecture. While the functional impacts of TE-derived sequences on early embryogenesis have been recognized, their roles in malignancy are only starting to emerge. Here we show that many TEs, especially the pluripotency-related human endogenous retrovirus H (HERVH), are abnormally activated in colorectal cancer (CRC) samples. Transcriptional upregulation of HERVH is associated with mutations of several tumor suppressors, particularly ARID1A. Knockout of ARID1A in CRC cells leads to increased transcription at several HERVH loci, which involves compensatory contribution by ARID1B. Suppression of HERVH in CRC cells and patient-derived organoids impairs tumor growth. Mechanistically, HERVH transcripts colocalize with nuclear BRD4 foci, modulating their dynamics and co-regulating many target genes. Altogether, we uncover a critical role for ARID1A in restraining HERVH, whose abnormal activation can promote tumorigenesis by stimulating BRD4-dependent transcription. Here the authors show mutation of the BAF chromatin remodeler subunit ARID1A results in an ARID1B-dependent upregulation of HERVH, an ERV required for the pluripotency regulatory network. These HERVH RNAs can partition into BRD4 foci, affecting BRD4-dependent transcription. Suppression of HERVH in colorectal cancer cells and patient-derived organoids impairs tumor growth.
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Affiliation(s)
- Chunhong Yu
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Xiaoyun Lei
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Fang Chen
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Song Mao
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Lu Lv
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Honglu Liu
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Xueying Hu
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Runhan Wang
- Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Licong Shen
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan, China.,Department of Gynecology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Na Zhang
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Yang Meng
- Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Yunfan Shen
- Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Jiale Chen
- Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Pishun Li
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Shi Huang
- Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Changwei Lin
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan, China.,Department of Gastrointestinal Surgery, The Third Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Zhuohua Zhang
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan, China.,Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China.,National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Kai Yuan
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan, China. .,Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China. .,National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan, China. .,The Biobank of Xiangya Hospital, Central South University, Changsha, Hunan, China.
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15
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Shindo Y, Brown MG, Amodeo AA. Versatile roles for histones in early development. Curr Opin Cell Biol 2022; 75:102069. [PMID: 35279563 PMCID: PMC9064922 DOI: 10.1016/j.ceb.2022.02.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 01/30/2022] [Accepted: 02/04/2022] [Indexed: 11/28/2022]
Abstract
The nuclear environment changes dramatically over the course of early development. Histones are core chromatin components that play critical roles in regulating gene expression and nuclear architecture. Additionally, the embryos of many species, including Drosophila, Zebrafish, and Xenopus use the availability of maternally deposited histones to time critical early embryonic events including cell cycle slowing and zygotic genome activation. Here, we review recent insights into how histones control early development. We first discuss the regulation of chromatin functions through interaction of histones and transcription factors, incorporation of variant histones, and histone post-translational modifications. We also highlight emerging roles for histones as developmental regulators independent of chromatin association.
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Affiliation(s)
- Yuki Shindo
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA.
| | - Madeleine G Brown
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA
| | - Amanda A Amodeo
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA.
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16
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Vernizzi L, Lehner CF. Bivalent individualization during chromosome territory formation in Drosophila spermatocytes by controlled condensin II protein activity and additional force generators. PLoS Genet 2021; 17:e1009870. [PMID: 34669718 PMCID: PMC8559962 DOI: 10.1371/journal.pgen.1009870] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Revised: 11/01/2021] [Accepted: 10/11/2021] [Indexed: 12/12/2022] Open
Abstract
Reduction of genome ploidy from diploid to haploid necessitates stable pairing of homologous chromosomes into bivalents before the start of the first meiotic division. Importantly, this chromosome pairing must avoid interlocking of non-homologous chromosomes. In spermatocytes of Drosophila melanogaster, where homolog pairing does not involve synaptonemal complex formation and crossovers, associations between non-homologous chromosomes are broken up by chromosome territory formation in early spermatocytes. Extensive non-homologous associations arise from the coalescence of the large blocks of pericentromeric heterochromatin into a chromocenter and from centromere clustering. Nevertheless, during territory formation, bivalents are moved apart into spatially separate subnuclear regions. The condensin II subunits, Cap-D3 and Cap-H2, have been implicated, but the remarkable separation of bivalents during interphase might require more than just condensin II. For further characterization of this process, we have applied time-lapse imaging using fluorescent markers of centromeres, telomeres and DNA satellites in pericentromeric heterochromatin. We describe the dynamics of the disruption of centromere clusters and the chromocenter in normal spermatocytes. Mutations in Cap-D3 and Cap-H2 abolish chromocenter disruption, resulting in excessive chromosome missegregation during M I. Chromocenter persistence in the mutants is not mediated by the special system, which conjoins homologs in compensation for the absence of crossovers in Drosophila spermatocytes. However, overexpression of Cap-H2 precluded conjunction between autosomal homologs, resulting in random segregation of univalents. Interestingly, Cap-D3 and Cap-H2 mutant spermatocytes displayed conspicuous stretching of the chromocenter, as well as occasional chromocenter disruption, suggesting that territory formation might involve forces unrelated to condensin II. While the molecular basis of these forces remains to be clarified, they are not destroyed by inhibitors of F actin and microtubules. Our results indicate that condensin II activity promotes chromosome territory formation in co-operation with additional force generators and that careful co-ordination with alternative homolog conjunction is crucial.
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Affiliation(s)
- Luisa Vernizzi
- Department of Molecular Life Science (DMLS), University of Zurich, Zurich, Switzerland
| | - Christian F. Lehner
- Department of Molecular Life Science (DMLS), University of Zurich, Zurich, Switzerland
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17
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Abstract
The imaging of chromatin, genomic loci, RNAs, and proteins is very important to study their localization, interaction, and coordinated regulation. Recently, several clustered regularly interspaced short palindromic repeats (CRISPR) based imaging methods have been established. The refurbished tool kits utilizing deactivated Cas9 (dCas9) and dCas13 have been established to develop applications of CRISPR-Cas technology beyond genome editing. Here, we review recent advancements in CRISPR-based methods that enable efficient imaging and visualization of chromatin, genomic loci, RNAs, and proteins. RNA aptamers, Pumilio, SuperNova tagging system, molecular beacons, halotag, bimolecular fluorescence complementation, RNA-guided endonuclease in situ labeling, and oligonucleotide-based imaging methods utilizing fluorescent proteins, organic dyes, or quantum dots have been developed to achieve improved fluorescence and signal-to-noise ratio for the imaging of chromatin or genomic loci. RNA-guided RNA targeting CRISPR systems (CRISPR/dCas13) and gene knock-in strategies based on CRISPR/Cas9 mediated site-specific cleavage and DNA repair mechanisms have been employed for efficient RNA and protein imaging, respectively. A few CRISPR-Cas-based methods to investigate the coordinated regulation of DNA-protein, DNA-RNA, or RNA-protein interactions for understanding chromatin dynamics, transcription, and protein function are also available. Overall, the CRISPR-based methods offer a significant improvement in elucidating chromatin organization and dynamics, RNA visualization, and protein imaging. The current and future advancements in CRISPR-based imaging techniques can revolutionize genome biology research for various applications.
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Affiliation(s)
- Vikram Singh
- School of Computational & Integrative Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Mukesh Jain
- School of Computational & Integrative Sciences, Jawaharlal Nehru University, New Delhi, India
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18
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Fabry MH, Falconio FA, Joud F, Lythgoe EK, Czech B, Hannon GJ. Maternally inherited piRNAs direct transient heterochromatin formation at active transposons during early Drosophila embryogenesis. eLife 2021; 10:e68573. [PMID: 34236313 PMCID: PMC8352587 DOI: 10.7554/elife.68573] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Accepted: 07/07/2021] [Indexed: 12/12/2022] Open
Abstract
The PIWI-interacting RNA (piRNA) pathway controls transposon expression in animal germ cells, thereby ensuring genome stability over generations. In Drosophila, piRNAs are intergenerationally inherited through the maternal lineage, and this has demonstrated importance in the specification of piRNA source loci and in silencing of I- and P-elements in the germ cells of daughters. Maternally inherited Piwi protein enters somatic nuclei in early embryos prior to zygotic genome activation and persists therein for roughly half of the time required to complete embryonic development. To investigate the role of the piRNA pathway in the embryonic soma, we created a conditionally unstable Piwi protein. This enabled maternally deposited Piwi to be cleared from newly laid embryos within 30 min and well ahead of the activation of zygotic transcription. Examination of RNA and protein profiles over time, and correlation with patterns of H3K9me3 deposition, suggests a role for maternally deposited Piwi in attenuating zygotic transposon expression in somatic cells of the developing embryo. In particular, robust deposition of piRNAs targeting roo, an element whose expression is mainly restricted to embryonic development, results in the deposition of transient heterochromatic marks at active roo insertions. We hypothesize that roo, an extremely successful mobile element, may have adopted a lifestyle of expression in the embryonic soma to evade silencing in germ cells.
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Affiliation(s)
- Martin H Fabry
- CRUK Cambridge Institute, University of Cambridge, Li Ka Shing CentreCambridgeUnited Kingdom
| | - Federica A Falconio
- CRUK Cambridge Institute, University of Cambridge, Li Ka Shing CentreCambridgeUnited Kingdom
| | - Fadwa Joud
- CRUK Cambridge Institute, University of Cambridge, Li Ka Shing CentreCambridgeUnited Kingdom
| | - Emily K Lythgoe
- CRUK Cambridge Institute, University of Cambridge, Li Ka Shing CentreCambridgeUnited Kingdom
| | - Benjamin Czech
- CRUK Cambridge Institute, University of Cambridge, Li Ka Shing CentreCambridgeUnited Kingdom
| | - Gregory J Hannon
- CRUK Cambridge Institute, University of Cambridge, Li Ka Shing CentreCambridgeUnited Kingdom
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19
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Wei KHC, Chan C, Bachtrog D. Establishment of H3K9me3-dependent heterochromatin during embryogenesis in Drosophila miranda. eLife 2021; 10:55612. [PMID: 34128466 PMCID: PMC8285105 DOI: 10.7554/elife.55612] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Accepted: 06/14/2021] [Indexed: 12/27/2022] Open
Abstract
Heterochromatin is a key architectural feature of eukaryotic genomes crucial for silencing of repetitive elements. During Drosophila embryonic cellularization, heterochromatin rapidly appears over repetitive sequences, but the molecular details of how heterochromatin is established are poorly understood. Here, we map the genome-wide distribution of H3K9me3-dependent heterochromatin in individual embryos of Drosophila miranda at precisely staged developmental time points. We find that canonical H3K9me3 enrichment is established prior to cellularization and matures into stable and broad heterochromatin domains through development. Intriguingly, initial nucleation sites of H3K9me3 enrichment appear as early as embryonic stage 3 over transposable elements (TEs) and progressively broaden, consistent with spreading to neighboring nucleosomes. The earliest nucleation sites are limited to specific regions of a small number of recently active retrotransposon families and often appear over promoter and 5' regions of LTR retrotransposons, while late nucleation sites develop broadly across the entirety of most TEs. Interestingly, early nucleating TEs are strongly associated with abundant maternal piRNAs and show early zygotic transcription. These results support a model of piRNA-associated co-transcriptional silencing while also suggesting additional mechanisms for site-restricted H3K9me3 nucleation at TEs in pre-cellular Drosophila embryos.
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Affiliation(s)
- Kevin H-C Wei
- Department of Integrative Biology, University of California, Berkeley, Berkeley, United States
| | - Carolus Chan
- Department of Integrative Biology, University of California, Berkeley, Berkeley, United States
| | - Doris Bachtrog
- Department of Integrative Biology, University of California, Berkeley, Berkeley, United States
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20
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Child MB, Bateman JR, Jahangiri A, Reimer A, Lammers NC, Sabouni N, Villamarin D, McKenzie-Smith GC, Johnson JE, Jost D, Garcia HG. Live imaging and biophysical modeling support a button-based mechanism of somatic homolog pairing in Drosophila. eLife 2021; 10:64412. [PMID: 34100718 PMCID: PMC8294847 DOI: 10.7554/elife.64412] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Accepted: 06/07/2021] [Indexed: 12/22/2022] Open
Abstract
Three-dimensional eukaryotic genome organization provides the structural basis for gene regulation. In Drosophila melanogaster, genome folding is characterized by somatic homolog pairing, where homologous chromosomes are intimately paired from end to end; however, how homologs identify one another and pair has remained mysterious. Recently, this process has been proposed to be driven by specifically interacting 'buttons' encoded along chromosomes. Here, we turned this hypothesis into a quantitative biophysical model to demonstrate that a button-based mechanism can lead to chromosome-wide pairing. We tested our model using live-imaging measurements of chromosomal loci tagged with the MS2 and PP7 nascent RNA labeling systems. We show solid agreement between model predictions and experiments in the pairing dynamics of individual homologous loci. Our results strongly support a button-based mechanism of somatic homolog pairing in Drosophila and provide a theoretical framework for revealing the molecular identity and regulation of buttons.
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Affiliation(s)
- Myron Barber Child
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States.,Department of Physics, University of California, Berkeley, Berkeley, United States
| | - Jack R Bateman
- Biology Department, Bowdoin College, Brunswick, United States
| | - Amir Jahangiri
- Univ Grenoble Alpes CNRS, Grenoble INP, TIMC-IMAG, Grenoble, France
| | - Armando Reimer
- Biophysics Graduate Group, University of California, Berkeley, Berkeley, United States
| | - Nicholas C Lammers
- Biophysics Graduate Group, University of California, Berkeley, Berkeley, United States
| | - Nica Sabouni
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | | | | | | | - Daniel Jost
- Univ Grenoble Alpes CNRS, Grenoble INP, TIMC-IMAG, Grenoble, France.,Université de Lyon, ENS de Lyon, Univ Claude Bernard, CNRS, Laboratory of Biology and Modeling of the Cell, Lyon, France
| | - Hernan G Garcia
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States.,Department of Physics, University of California, Berkeley, Berkeley, United States.,Biophysics Graduate Group, University of California, Berkeley, Berkeley, United States.,Institute for Quantitative Biosciences-QB3, University of California, Berkeley, Berkeley, United States
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21
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Keenen MM, Brown D, Brennan LD, Renger R, Khoo H, Carlson CR, Huang B, Grill SW, Narlikar GJ, Redding S. HP1 proteins compact DNA into mechanically and positionally stable phase separated domains. eLife 2021; 10:e64563. [PMID: 33661100 PMCID: PMC7932698 DOI: 10.7554/elife.64563] [Citation(s) in RCA: 101] [Impact Index Per Article: 33.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Accepted: 02/22/2021] [Indexed: 12/11/2022] Open
Abstract
In mammals, HP1-mediated heterochromatin forms positionally and mechanically stable genomic domains even though the component HP1 paralogs, HP1α, HP1β, and HP1γ, display rapid on-off dynamics. Here, we investigate whether phase-separation by HP1 proteins can explain these biological observations. Using bulk and single-molecule methods, we show that, within phase-separated HP1α-DNA condensates, HP1α acts as a dynamic liquid, while compacted DNA molecules are constrained in local territories. These condensates are resistant to large forces yet can be readily dissolved by HP1β. Finally, we find that differences in each HP1 paralog's DNA compaction and phase-separation properties arise from their respective disordered regions. Our findings suggest a generalizable model for genome organization in which a pool of weakly bound proteins collectively capitalize on the polymer properties of DNA to produce self-organizing domains that are simultaneously resistant to large forces at the mesoscale and susceptible to competition at the molecular scale.
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Affiliation(s)
- Madeline M Keenen
- Department of Biochemistry and Biophysics, University of California, San FranciscoSan FranciscoUnited States
- Tetrad Graduate Program, University of California, San FranciscoSan FranciscoUnited States
| | - David Brown
- Department of Pharmaceutical Chemistry, University of California, San FranciscoSan FranciscoUnited States
| | - Lucy D Brennan
- Department of Biochemistry and Biophysics, University of California, San FranciscoSan FranciscoUnited States
| | - Roman Renger
- Max Planck Institute of Molecular Cell Biology and GeneticsDresdenGermany
- German Center for Neurodegenerative Diseases (DZNE)BonnGermany
| | - Harrison Khoo
- Department of Mechanical Engineering, Johns Hopkins UniversityBaltimoreUnited States
| | - Christopher R Carlson
- Tetrad Graduate Program, University of California, San FranciscoSan FranciscoUnited States
- Department of Physiology, University of California, San FranciscoSan FranciscoUnited States
| | - Bo Huang
- Department of Biochemistry and Biophysics, University of California, San FranciscoSan FranciscoUnited States
- Department of Pharmaceutical Chemistry, University of California, San FranciscoSan FranciscoUnited States
- Chan Zuckerberg BiohubSan FranciscoUnited States
| | - Stephan W Grill
- Max Planck Institute of Molecular Cell Biology and GeneticsDresdenGermany
- Cluster of Excellence Physics of Life, Technische Universität DresdenDresdenGermany
| | - Geeta J Narlikar
- Department of Biochemistry and Biophysics, University of California, San FranciscoSan FranciscoUnited States
| | - Sy Redding
- Department of Biochemistry and Biophysics, University of California, San FranciscoSan FranciscoUnited States
- Marine Biological LaboratoryWoods HoleUnited States
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22
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Lauria Sneideman MP, Meller VH. Drosophila Satellite Repeats at the Intersection of Chromatin, Gene Regulation and Evolution. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2021; 60:1-26. [PMID: 34386870 DOI: 10.1007/978-3-030-74889-0_1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Satellite repeats make up a large fraction of the genomes of many higher eukaryotes. Until recently these sequences were viewed as molecular parasites with few functions. Drosophila melanogaster and related species have a wealth of diverse satellite repeats. Comparative studies of Drosophilids have been instrumental in understanding how these rapidly evolving sequences change and move. Remarkably, satellite repeats have been found to modulate gene expression and mediate genetic conflicts between chromosomes and between closely related fly species. This suggests that satellites play a key role in speciation. We have taken advantage of the depth of research on satellite repeats in flies to review the known functions of these sequences and consider their central role in evolution and gene expression.
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Affiliation(s)
| | - Victoria H Meller
- Department of Biological Sciences, Wayne State University, Detroit, MI, USA.
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23
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Wei KHC, Gibilisco L, Bachtrog D. Epigenetic conflict on a degenerating Y chromosome increases mutational burden in Drosophila males. Nat Commun 2020; 11:5537. [PMID: 33139741 PMCID: PMC7608633 DOI: 10.1038/s41467-020-19134-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Accepted: 09/24/2020] [Indexed: 01/04/2023] Open
Abstract
Large portions of eukaryotic genomes consist of transposable elements (TEs), and the establishment of transcription-repressing heterochromatin during early development safeguards genome integrity in Drosophila. Repeat-rich Y chromosomes can act as reservoirs for TEs ('toxic' Y effect), and incomplete epigenomic defenses during early development can lead to deleterious TE mobilization. Here, we contrast the dynamics of early TE activation in two Drosophila species with vastly different Y chromosomes of different ages. Zygotic TE expression is elevated in male embryos relative to females in both species, mostly due to expression of Y-linked TEs. Interestingly, male-biased TE expression diminishes across development in D. pseudoobscura, but remains elevated in D. miranda, the species with the younger and larger Y chromosome. The repeat-rich Y of D. miranda still contains many actively transcribed genes, which compromise the formation of silencing heterochromatin. Elevated TE expression results in more de novo insertions of repeats in males compared to females. This lends support to the idea that the 'toxic' Y chromosome can create a mutational burden in males when genome-wide defense mechanisms are compromised, and suggests a previously unappreciated epigenetic conflict on evolving Y chromosomes between transcription of essential genes and silencing of selfish DNA.
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Affiliation(s)
- Kevin H-C Wei
- Department of Integrative Biology, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Lauren Gibilisco
- Department of Integrative Biology, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Doris Bachtrog
- Department of Integrative Biology, University of California Berkeley, Berkeley, CA, 94720, USA.
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24
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Ryder PV, Lerit DA. Quantitative analysis of subcellular distributions with an open-source, object-based tool. Biol Open 2020; 9:bio055228. [PMID: 32973081 PMCID: PMC7595693 DOI: 10.1242/bio.055228] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 09/17/2020] [Indexed: 01/02/2023] Open
Abstract
The subcellular localization of objects, such as organelles, proteins, or other molecules, instructs cellular form and function. Understanding the underlying spatial relationships between objects through colocalization analysis of microscopy images is a fundamental approach used to inform biological mechanisms. We generated an automated and customizable computational tool, the SubcellularDistribution pipeline, to facilitate object-based image analysis from three-dimensional (3D) fluorescence microcopy images. To test the utility of the SubcellularDistribution pipeline, we examined the subcellular distribution of mRNA relative to centrosomes within syncytial Drosophila embryos. Centrosomes are microtubule-organizing centers, and RNA enrichments at centrosomes are of emerging importance. Our open-source and freely available software detected RNA distributions comparably to commercially available image analysis software. The SubcellularDistribution pipeline is designed to guide the user through the complete process of preparing image analysis data for publication, from image segmentation and data processing to visualization.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Pearl V Ryder
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Dorothy A Lerit
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
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25
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Strong IJT, Lei X, Chen F, Yuan K, O’Farrell PH. Interphase-arrested Drosophila embryos activate zygotic gene expression and initiate mid-blastula transition events at a low nuclear-cytoplasmic ratio. PLoS Biol 2020; 18:e3000891. [PMID: 33090988 PMCID: PMC7608951 DOI: 10.1371/journal.pbio.3000891] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 11/03/2020] [Accepted: 09/14/2020] [Indexed: 11/18/2022] Open
Abstract
Externally deposited eggs begin development with an immense cytoplasm and a single overwhelmed nucleus. Rapid mitotic cycles restore normality as the ratio of nuclei to cytoplasm (N/C) increases. A threshold N/C has been widely proposed to activate zygotic genome transcription and onset of morphogenesis at the mid-blastula transition (MBT). To test whether a threshold N/C is required for these events, we blocked N/C increase by down-regulating cyclin/Cdk1 to arrest early cell cycles in Drosophila. Embryos that were arrested two cell cycles prior to the normal MBT activated widespread transcription of the zygotic genome including genes previously described as N/C dependent. Zygotic transcription of these genes largely retained features of their regulation in space and time. Furthermore, zygotically regulated post-MBT events such as cellularization and gastrulation movements occurred in these cell cycle-arrested embryos. These results are not compatible with models suggesting that these MBT events are directly coupled to N/C. Cyclin/Cdk1 activity normally declines in tight association with increasing N/C and is regulated by N/C. By experimentally promoting the decrease in cyclin/Cdk1, we uncoupled MBT from N/C increase, arguing that N/C-guided down-regulation of cyclin/Cdk1 is sufficient for genome activation and MBT.
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Affiliation(s)
- Isaac J. T. Strong
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, United States of America
| | - Xiaoyun Lei
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Fang Chen
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Kai Yuan
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Oncology, Xiangya Hospital, Central South University, Changsha, Hunan, China
- Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Patrick H. O’Farrell
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, United States of America
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26
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Reinig J, Ruge F, Howard M, Ringrose L. A theoretical model of Polycomb/Trithorax action unites stable epigenetic memory and dynamic regulation. Nat Commun 2020; 11:4782. [PMID: 32963223 PMCID: PMC7508846 DOI: 10.1038/s41467-020-18507-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Accepted: 08/24/2020] [Indexed: 12/12/2022] Open
Abstract
Polycomb and Trithorax group proteins maintain stable epigenetic memory of gene expression states for some genes, but many targets show highly dynamic regulation. Here we combine experiment and theory to examine the mechanistic basis of these different modes of regulation. We present a mathematical model comprising a Polycomb/Trithorax response element (PRE/TRE) coupled to a promoter and including Drosophila developmental timing. The model accurately recapitulates published studies of PRE/TRE mediated epigenetic memory of both silencing and activation. With minimal parameter changes, the same model can also recapitulate experimental data for a different PRE/TRE that allows dynamic regulation of its target gene. The model predicts that both cell cycle length and PRE/TRE identity are critical for determining whether the system gives stable memory or dynamic regulation. Our work provides a simple unifying framework for a rich repertoire of PRE/TRE functions, and thus provides insights into genome-wide Polycomb/Trithorax regulation. Polycomb (PcG) and Trithorax (TrxG) group regulate several hundred target genes with important roles in development and disease. Here the authors combine experiment and theory to provide evidence that the Polycomb/Trithorax system has the potential for a rich repertoire of regulatory modes beyond simple epigenetic memory.
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Affiliation(s)
- Jeannette Reinig
- Humboldt Universität zu Berlin, IRI- Lifesciences, Philippstr. 13, 10115, Berlin, Germany
| | - Frank Ruge
- IMBA, Institute of Molecular Biotechnology, Dr. Bohr- Gasse 3, 1030, Vienna, Austria
| | - Martin Howard
- John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK
| | - Leonie Ringrose
- Humboldt Universität zu Berlin, IRI- Lifesciences, Philippstr. 13, 10115, Berlin, Germany. .,IMBA, Institute of Molecular Biotechnology, Dr. Bohr- Gasse 3, 1030, Vienna, Austria.
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27
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Liu J, Ali M, Zhou Q. Establishment and evolution of heterochromatin. Ann N Y Acad Sci 2020; 1476:59-77. [PMID: 32017156 PMCID: PMC7586837 DOI: 10.1111/nyas.14303] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 10/31/2019] [Accepted: 01/02/2020] [Indexed: 12/12/2022]
Abstract
The eukaryotic genome is packaged into transcriptionally active euchromatin and silent heterochromatin, with most studies focused on the former encompassing the majority of protein-coding genes. The recent development of various sequencing techniques has refined this classic dichromatic partition and has better illuminated the composition, establishment, and evolution of this genomic and epigenomic "dark matter" in the context of topologically associated domains and phase-separated droplets. Heterochromatin includes genomic regions that can be densely stained by chemical dyes, which have been shown to be enriched for repetitive elements and epigenetic marks, including H3K9me2/3 and H3K27me3. Heterochromatin is usually replicated late, concentrated at the nuclear periphery or around nucleoli, and usually lacks highly expressed genes; and now it is considered to be as neither genetically inert nor developmentally static. Heterochromatin guards genome integrity against transposon activities and exerts important regulatory functions by targeting beyond its contained genes. Both its nucleotide sequences and regulatory proteins exhibit rapid coevolution between species. In addition, there are dynamic transitions between euchromatin and heterochromatin during developmental and evolutionary processes. We summarize here the ever-changing characteristics of heterochromatin and propose models and principles for the evolutionary transitions of heterochromatin that have been mainly learned from studies of Drosophila and yeast. Finally, we highlight the role of sex chromosomes in studying heterochromatin evolution.
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Affiliation(s)
- Jing Liu
- MOE Laboratory of Biosystems Homeostasis & Protection, Life Sciences InstituteZhejiang UniversityHangzhouChina
- Department of Molecular Evolution and DevelopmentUniversity of ViennaViennaAustria
| | - Mujahid Ali
- Department of Molecular Evolution and DevelopmentUniversity of ViennaViennaAustria
| | - Qi Zhou
- MOE Laboratory of Biosystems Homeostasis & Protection, Life Sciences InstituteZhejiang UniversityHangzhouChina
- Department of Molecular Evolution and DevelopmentUniversity of ViennaViennaAustria
- Center for Reproductive Medicine, The 2nd Affiliated Hospital, School of MedicineZhejiang UniversityHangzhouChina
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28
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Tang R, Jiang Z, Chen F, Yu W, Fan K, Tan J, Zhang Z, Liu X, Li P, Yuan K. The Kinase Activity of Drosophila BubR1 Is Required for Insulin Signaling-Dependent Stem Cell Maintenance. Cell Rep 2020; 31:107794. [PMID: 32579921 DOI: 10.1016/j.celrep.2020.107794] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 04/29/2020] [Accepted: 05/31/2020] [Indexed: 02/06/2023] Open
Abstract
As a core component of the mitotic checkpoint complex, BubR1 has a modular organization of molecular functions, with KEN box and other motifs at the N terminus inhibiting the anaphase-promoting complex/cyclosome, and a kinase domain at the C terminus, whose function remains unsettled, especially at organismal levels. We generate knock-in BubR1 mutations in the Drosophila genome to separately disrupt the KEN box and the kinase domain. All of the mutants are homozygously viable and fertile and show no defects in mitotic progression. The mutants without kinase activity have an increased lifespan and phenotypic changes associated with attenuated insulin signaling, including reduced InR on the cell membrane, weakened PI3K and AKT activity, and elevated expression of dFoxO targets. The BubR1 kinase-dead mutants have a reduced cap cell number in female germaria, which can be rescued by expressing a constitutively active InR. We conclude that one major physiological role of BubR1 kinase in Drosophila is to modulate insulin signaling.
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Affiliation(s)
- Ruijun Tang
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Neurosurgery, Xiangya Hospital, and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China
| | - Zhenghui Jiang
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Neurosurgery, Xiangya Hospital, and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China
| | - Fang Chen
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Neurosurgery, Xiangya Hospital, and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Weiyu Yu
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Neurosurgery, Xiangya Hospital, and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China
| | - Kaijing Fan
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Neurosurgery, Xiangya Hospital, and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China
| | - Jieqiong Tan
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Neurosurgery, Xiangya Hospital, and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China
| | - Zhuohua Zhang
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Neurosurgery, Xiangya Hospital, and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China
| | - Xing Liu
- MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China.
| | - Pishun Li
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Neurosurgery, Xiangya Hospital, and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Kai Yuan
- Hunan Key Laboratory of Molecular Precision Medicine, Department of Neurosurgery, Xiangya Hospital, and Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China; Center for Clinical Biorepositories and Biospecimens, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China.
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29
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Walther M, Schrahn S, Krauss V, Lein S, Kessler J, Jenuwein T, Reuter G. Heterochromatin formation in Drosophila requires genome-wide histone deacetylation in cleavage chromatin before mid-blastula transition in early embryogenesis. Chromosoma 2020; 129:83-98. [PMID: 31950239 PMCID: PMC7021753 DOI: 10.1007/s00412-020-00732-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 12/13/2019] [Accepted: 01/02/2020] [Indexed: 02/05/2023]
Abstract
Su(var) mutations define epigenetic factors controlling heterochromatin formation and gene silencing in Drosophila. Here, we identify SU(VAR)2-1 as a novel chromatin regulator that directs global histone deacetylation during the transition of cleavage chromatin into somatic blastoderm chromatin in early embryogenesis. SU(VAR)2-1 is heterochromatin-associated in blastoderm nuclei but not in later stages of development. In larval polytene chromosomes, SU(VAR)2-1 is a band-specific protein. SU(VAR)2-1 directs global histone deacetylation by recruiting the histone deacetylase RPD3. In Su(var)2-1 mutants H3K9, H3K27, H4K8 and H4K16 acetylation shows elevated levels genome-wide and heterochromatin displays aberrant histone hyper-acetylation. Whereas H3K9me2- and HP1a-binding appears unaltered, the heterochromatin-specific H3K9me2S10ph composite mark is impaired in heterochromatic chromocenters of larval salivary polytene chromosomes. SU(VAR)2-1 contains an NRF1/EWG domain and a C2HC zinc-finger motif. Our study identifies SU(VAR)2-1 as a dosage-dependent, heterochromatin-initiating SU(VAR) factor, where the SU(VAR)2-1-mediated control of genome-wide histone deacetylation after cleavage and before mid-blastula transition (pre-MBT) is required to enable heterochromatin formation.
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Affiliation(s)
- Matthias Walther
- Developmental Genetics, Institute of Biology, Martin Luther University Halle, Weinbergweg 10, 06120, Halle/S., Germany
- Max Planck Institute of Immunobiology and Epigenetics, Stübeweg 51, 79108, Freiburg, Germany
| | - Sandy Schrahn
- Developmental Genetics, Institute of Biology, Martin Luther University Halle, Weinbergweg 10, 06120, Halle/S., Germany
| | - Veiko Krauss
- Cluster of Excellence in Plant Science (CEPLAS), University of Cologne, Biocenter, 50674, Cologne, Germany
| | - Sandro Lein
- Developmental Genetics, Institute of Biology, Martin Luther University Halle, Weinbergweg 10, 06120, Halle/S., Germany
| | - Jeannette Kessler
- Developmental Genetics, Institute of Biology, Martin Luther University Halle, Weinbergweg 10, 06120, Halle/S., Germany
| | - Thomas Jenuwein
- Max Planck Institute of Immunobiology and Epigenetics, Stübeweg 51, 79108, Freiburg, Germany
| | - Gunter Reuter
- Developmental Genetics, Institute of Biology, Martin Luther University Halle, Weinbergweg 10, 06120, Halle/S., Germany.
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30
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Mills WK, Lee YCG, Kochendoerfer AM, Dunleavy EM, Karpen GH. RNA from a simple-tandem repeat is required for sperm maturation and male fertility in Drosophila melanogaster. eLife 2019; 8:48940. [PMID: 31687931 PMCID: PMC6879302 DOI: 10.7554/elife.48940] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 11/03/2019] [Indexed: 11/26/2022] Open
Abstract
Tandemly-repeated DNAs, or satellites, are enriched in heterochromatic regions of eukaryotic genomes and contribute to nuclear structure and function. Some satellites are transcribed, but we lack direct evidence that specific satellite RNAs are required for normal organismal functions. Here, we show satellite RNAs derived from AAGAG tandem repeats are transcribed in many cells throughout Drosophila melanogaster development, enriched in neurons and testes, often localized within heterochromatic regions, and important for viability. Strikingly, we find AAGAG transcripts are necessary for male fertility, and that AAGAG RNA depletion results in defective histone-protamine exchange, sperm maturation and chromatin organization. Since these events happen late in spermatogenesis when the transcripts are not detected, we speculate that AAGAG RNA in primary spermatocytes ‘primes’ post-meiosis steps for sperm maturation. In addition to demonstrating essential functions for AAGAG RNAs, comparisons between closely related Drosophila species suggest that satellites and their transcription evolve quickly to generate new functions.
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Affiliation(s)
- Wilbur Kyle Mills
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States.,Lawrence Berkeley National Laboratory, Berkeley, United States
| | - Yuh Chwen G Lee
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States.,Lawrence Berkeley National Laboratory, Berkeley, United States.,Department of Ecology and Evolutionary Biology, University of California, Irvine, Irvine, United States
| | | | - Elaine M Dunleavy
- Centre for Chromosome Biology, National University of Ireland, Galway, Ireland
| | - Gary H Karpen
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
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31
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Benner L, Castro EA, Whitworth C, Venken KJT, Yang H, Fang J, Oliver B, Cook KR, Lerit DA. Drosophila Heterochromatin Stabilization Requires the Zinc-Finger Protein Small Ovary. Genetics 2019; 213:877-895. [PMID: 31558581 PMCID: PMC6827387 DOI: 10.1534/genetics.119.302590] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Accepted: 09/21/2019] [Indexed: 02/04/2023] Open
Abstract
Heterochromatin-mediated repression is essential for controlling the expression of transposons and for coordinated cell type-specific gene regulation. The small ovary (sov) locus was identified in a screen for female-sterile mutations in Drosophila melanogaster, and mutants show dramatic ovarian morphogenesis defects. We show that the null sov phenotype is lethal and map the locus to the uncharacterized gene CG14438, which encodes a nuclear zinc-finger protein that colocalizes with the essential Heterochromatin Protein 1 (HP1a). We demonstrate Sov functions to repress inappropriate gene expression in the ovary, silence transposons, and suppress position-effect variegation in the eye, suggesting a central role in heterochromatin stabilization.
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Affiliation(s)
- Leif Benner
- Section of Developmental Genomics, Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
- Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218
| | - Elias A Castro
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Cale Whitworth
- Section of Developmental Genomics, Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
- Department of Biology, Indiana University, Bloomington, Indiana 47405
| | - Koen J T Venken
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology
- McNair Medical Institute at the Robert and Janice McNair Foundation
- Dan L. Duncan Cancer Center, Center for Drug Discovery
- Department of Pharmacology and Chemical Biology, Baylor College of Medicine, Houston, Texas 77030
| | - Haiwang Yang
- Section of Developmental Genomics, Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Junnan Fang
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Brian Oliver
- Section of Developmental Genomics, Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Kevin R Cook
- Department of Biology, Indiana University, Bloomington, Indiana 47405
| | - Dorothy A Lerit
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322
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32
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Wu L, Jia Q, Zhang X, Zhang X, Liu S, Park Y, Feyereisen R, Zhu KY, Ma E, Zhang J, Li S. CYP303A1 has a conserved function in adult eclosion in Locusta migratoria and Drosophila melanogaster. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2019; 113:103210. [PMID: 31422152 DOI: 10.1016/j.ibmb.2019.103210] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 07/15/2019] [Accepted: 07/15/2019] [Indexed: 06/10/2023]
Abstract
Insect cytochrome P450 monooxygenases (CYPs) play essential roles in both xenobiotic metabolism and developmental processes. However, the exact physiological function of many CYP genes remains largely unknown. Screening the expression of the CYP genes from the CYP2 and mitochondrial CYP clans of Drosophila melanogaster revealed that Cyp303a1 is highly expressed in the pupal stage. Knockdown of CYP303A1 transcripts by RNAi using the Gal4/UAS system with a ubiquitous driver (tubulin-Gal4) in Drosophila or by dsRNA injection in the last nymph stage of Locusta migratoria resulted in severe defects in eclosion and lethality during and after adult emergence. In Drosophila, tissue-specific RNAi of Cyp303a1 with a wing-specific driver (MS1096-Gal4) revealed that Cyp303a1 was essential for wing extension. Stage-specific RNAi of Cyp303a1 using Gal80ts for thermal-dependent-suppression found that the expression of Cyp303a1 at the middle pupal stage was absolutely required. Meanwhile, Cyp303a1 mutants exhibited more than 80% lethality at the late embryonic development stages. Embryonic lethality of the Cyp303a1 mutants was fully rescued by the ubiquitous overexpression of exogenous Cyp303a1. Taken together, we conclude that Cyp303a1 is indispensable for embryonic development and adult eclosion in D. melanogaster, the latter role being conserved over 400 million years of insect evolution.
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Affiliation(s)
- Lixian Wu
- Research Institute of Applied Biology, Shanxi University, Taiyuan, Shanxi 030006, China; College of Life Science, Shanxi University, Taiyuan, Shanxi 030006, China; Guangdong Provincial Key Laboratory of Insect Development Biology and Applied Technology, Institute of Insect Science and Technology, School of Life Sciences, South China Normal University, Guangzhou 510631, China
| | - Qiangqiang Jia
- Guangdong Provincial Key Laboratory of Insect Development Biology and Applied Technology, Institute of Insect Science and Technology, School of Life Sciences, South China Normal University, Guangzhou 510631, China
| | - Xubo Zhang
- Research Institute of Applied Biology, Shanxi University, Taiyuan, Shanxi 030006, China
| | - Xueyao Zhang
- Research Institute of Applied Biology, Shanxi University, Taiyuan, Shanxi 030006, China
| | - Suning Liu
- Guangdong Provincial Key Laboratory of Insect Development Biology and Applied Technology, Institute of Insect Science and Technology, School of Life Sciences, South China Normal University, Guangzhou 510631, China
| | - Yoonseong Park
- Department of Entomology, Kansas State University, Manhattan, KS 66506, USA
| | - René Feyereisen
- Department of Plant and Environmental Sciences, University of Copenhagen, Copenhagen 1017, Denmark; Department of Plant and Crops, Ghent University, B-9000 Ghent, Belgium
| | - Kun Yan Zhu
- Department of Entomology, Kansas State University, Manhattan, KS 66506, USA
| | - Enbo Ma
- Research Institute of Applied Biology, Shanxi University, Taiyuan, Shanxi 030006, China
| | - Jianzhen Zhang
- Research Institute of Applied Biology, Shanxi University, Taiyuan, Shanxi 030006, China.
| | - Sheng Li
- Guangdong Provincial Key Laboratory of Insect Development Biology and Applied Technology, Institute of Insect Science and Technology, School of Life Sciences, South China Normal University, Guangzhou 510631, China.
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33
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Sato Y, Hilbert L, Oda H, Wan Y, Heddleston JM, Chew TL, Zaburdaev V, Keller P, Lionnet T, Vastenhouw N, Kimura H. Histone H3K27 acetylation precedes active transcription during zebrafish zygotic genome activation as revealed by live-cell analysis. Development 2019; 146:146/19/dev179127. [PMID: 31570370 PMCID: PMC6803375 DOI: 10.1242/dev.179127] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2019] [Accepted: 09/06/2019] [Indexed: 12/14/2022]
Abstract
Histone post-translational modifications are key gene expression regulators, but their rapid dynamics during development remain difficult to capture. We applied a Fab-based live endogenous modification labeling technique to monitor the changes in histone modification levels during zygotic genome activation (ZGA) in living zebrafish embryos. Among various histone modifications, H3 Lys27 acetylation (H3K27ac) exhibited most drastic changes, accumulating in two nuclear foci in the 64- to 1k-cell-stage embryos. The elongating form of RNA polymerase II, which is phosphorylated at Ser2 in heptad repeats within the C-terminal domain (RNAP2 Ser2ph), and miR-430 transcripts were also concentrated in foci closely associated with H3K27ac. When treated with α-amanitin to inhibit transcription or JQ-1 to inhibit binding of acetyl-reader proteins, H3K27ac foci still appeared but RNAP2 Ser2ph and miR-430 morpholino were not concentrated in foci, suggesting that H3K27ac precedes active transcription during ZGA. We anticipate that the method presented here could be applied to a variety of developmental processes in any model and non-model organisms.
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Affiliation(s)
- Yuko Sato
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8503, Japan
| | - Lennart Hilbert
- Center for Systems Biology Dresden, Dresden 01307, Germany.,Max Planck Institute for the Physics of Complex Systems, Dresden 01187, Germany.,Max Planck Institute of Molecular Cell Biology and Genetics, Dresden 01307, Germany
| | - Haruka Oda
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8503, Japan
| | - Yinan Wan
- Howard Hughes Medical Institute, Janelia Research Campus, VA 20147, USA
| | - John M Heddleston
- Advanced Imaging Center, Howard Hughes Medical Institute, Janelia Research Campus, VA 20147, USA
| | - Teng-Leong Chew
- Advanced Imaging Center, Howard Hughes Medical Institute, Janelia Research Campus, VA 20147, USA
| | - Vasily Zaburdaev
- Center for Systems Biology Dresden, Dresden 01307, Germany.,Max Planck Institute for the Physics of Complex Systems, Dresden 01187, Germany
| | - Philipp Keller
- Howard Hughes Medical Institute, Janelia Research Campus, VA 20147, USA
| | - Timothee Lionnet
- Institute for Systems Genetics and Department of Cell Biology, New York University Langone Health, NY 10016, USA
| | - Nadine Vastenhouw
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden 01307, Germany
| | - Hiroshi Kimura
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8503, Japan
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34
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Monitoring of switches in heterochromatin-induced silencing shows incomplete establishment and developmental instabilities. Proc Natl Acad Sci U S A 2019; 116:20043-20053. [PMID: 31527269 DOI: 10.1073/pnas.1909724116] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Position effect variegation (PEV) in Drosophila results from new juxtapositions of euchromatic and heterochromatic chromosomal regions, and manifests as striking bimodal patterns of gene expression. The semirandom patterns of PEV, reflecting clonal relationships between cells, have been interpreted as gene-expression states that are set in development and thereafter maintained without change through subsequent cell divisions. The rate of instability of PEV is almost entirely unexplored beyond the final expression of the modified gene; thus the origin of the expressivity and patterns of PEV remain unexplained. Many properties of PEV are not predicted from currently accepted biochemical and theoretical models. In this work we investigate the time at which expressivity of silencing is set, and find that it is determined before heterochromatin exists. We employ a mathematical simulation and a corroborating experimental approach to monitor switching (i.e., gains and losses of silencing) through development. In contrast to current views, we find that gene silencing is incompletely set early in embryogenesis, but nevertheless is repeatedly lost and gained in individual cells throughout development. Our data support an alternative to locus-specific "epigenetic" silencing at variegating gene promoters that more fully accounts for the final patterns of PEV.
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35
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van Steensel B, Furlong EEM. The role of transcription in shaping the spatial organization of the genome. Nat Rev Mol Cell Biol 2019; 20:327-337. [PMID: 30886333 PMCID: PMC7116054 DOI: 10.1038/s41580-019-0114-6] [Citation(s) in RCA: 125] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The spatial organization of the genome into compartments and topologically associated domains can have an important role in the regulation of gene expression. But could gene expression conversely regulate genome organization? Here, we review recent studies that assessed the requirement of transcription and/or the transcription machinery for the establishment or maintenance of genome topology. The results reveal different requirements at different genomic scales. Transcription is generally not required for higher-level genome compartmentalization, has only moderate effects on domain organization and is not sufficient to create new domain boundaries. However, on a finer scale, transcripts or transcription does seem to have a role in the formation of subcompartments and subdomains and in stabilizing enhancer-promoter interactions. Recent evidence suggests a dynamic, reciprocal interplay between fine-scale genome organization and transcription, in which each is able to modulate or reinforce the activity of the other.
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Affiliation(s)
- Bas van Steensel
- Division of Gene Regulation and Oncode Institute, Netherlands Cancer Institute, Amsterdam, Netherlands.
- Department of Cell Biology, Erasmus University Medical Centre, Rotterdam, Netherlands.
| | - Eileen E M Furlong
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Heidelberg, Germany.
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36
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Microinjection Techniques in Fly Embryos to Study the Function and Dynamics of SMC Complexes. Methods Mol Biol 2019. [PMID: 31147923 DOI: 10.1007/978-1-4939-9520-2_19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/07/2023]
Abstract
Structural maintenance of chromosomes (SMC) proteins are critical to maintain mitotic fidelity in all organisms. Over the last decades, acute inactivation of these complexes, together with the analysis of their dynamic binding to mitotic chromatin, has provided important insights on the molecular mechanism of these complexes as well as into the consequences of their failure at different stages of mitosis.Here, we describe a methodology to study both SMC function and dynamics using Drosophila melanogaster syncytial embryos. This system presents several advantages over canonical inactivation or imaging approaches. Efficient and fast inactivation of SMC complexes can be achieved by the use of tobacco etch virus (TEV) protease in vivo to cleave engineered versions of the SMC complexes. In contrast to genetically encoded TEV protease expression, Drosophila embryos enable prompt delivery of the protease by microinjection techniques, as detailed here, thereby allowing inactivation of the complexes within few minutes. Such an acute inactivation approach, when coupled with real-time imaging, allows for the analysis of the immediate consequences upon protein inactivation. As described here, this system also presents unique advantages to follow the kinetics of the loading of SMC complexes onto mitotic chromatin. We describe the use of Drosophila embryos to study localization and turnover of these molecules through live imaging and fluorescence recovery after photobleaching (FRAP) approaches.
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37
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Abstract
In this Perspective, Armstrong and Duronio discuss the findings in this issue of Genes & Developmnet by Seller et al., who developed a new technology for inhibiting maternal gene function to identify the H3K9 methyltransferase necessary for initiating constitutive heterochromatin formation during early Drosophila embryogenesis. Constitutive heterochromatin is a prevalent feature of eukaryotic genomes important for promoting cell differentiation and maintaining genome stability. During animal reproduction, constitutive heterochromatin is disassembled in gametes prior to formation of the zygote and then subsequently re-established as development ensues and cells differentiate. Despite progress in understanding the mechanisms that maintain heterochromatin in differentiated cell types, how constitutive heterochromatin is assembled de novo during early development remains poorly understood. In this issue of Genes & Development, Seller and colleagues (pp. 403–417) develop a new technology for inhibiting maternal gene function to identify the H3K9 methyltransferase necessary for initiating constitutive heterochromatin formation during early Drosophila embryogenesis.
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Affiliation(s)
- Robin L Armstrong
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - Robert J Duronio
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.,Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.,Department of Genetics, University of North Carolina, Chapel Hill, North Carolina 27599, USA.,Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, North Carolina 27599, USA.,Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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38
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Seller CA, Cho CY, O'Farrell PH. Rapid embryonic cell cycles defer the establishment of heterochromatin by Eggless/SetDB1 in Drosophila. Genes Dev 2019; 33:403-417. [PMID: 30808658 PMCID: PMC6446540 DOI: 10.1101/gad.321646.118] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 01/14/2019] [Indexed: 12/15/2022]
Abstract
Acquisition of chromatin modifications during embryogenesis distinguishes different regions of an initially naïve genome. In many organisms, repetitive DNA is packaged into constitutive heterochromatin that is marked by di/trimethylation of histone H3K9 and the associated protein HP1a. These modifications enforce the unique epigenetic properties of heterochromatin. However, in the early Drosophila melanogaster embryo, the heterochromatin lacks these modifications, which appear only later, when rapid embryonic cell cycles slow down at the midblastula transition (MBT). Here we focus on the initial steps restoring heterochromatic modifications in the embryo. We describe the JabbaTrap, a technique for inactivating maternally provided proteins in embryos. Using the JabbaTrap, we reveal a major requirement for the methyltransferase Eggless/SetDB1 in the establishment of heterochromatin. In contrast, other methyltransferases contribute minimally. Live imaging reveals that endogenous Eggless gradually accumulates on chromatin in interphase but then dissociates in mitosis, and its accumulation must restart in the next cell cycle. Cell cycle slowing as the embryo approaches the MBT permits increasing accumulation and action of Eggless at its targets. Experimental manipulation of interphase duration shows that cell cycle speed regulates Eggless. We propose that developmental slowing of the cell cycle times embryonic heterochromatin formation.
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Affiliation(s)
- Charles A Seller
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94143, USA
| | - Chun-Yi Cho
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94143, USA
| | - Patrick H O'Farrell
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94143, USA
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39
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Shindo Y, Amodeo AA. Dynamics of Free and Chromatin-Bound Histone H3 during Early Embryogenesis. Curr Biol 2019; 29:359-366.e4. [DOI: 10.1016/j.cub.2018.12.020] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Revised: 10/29/2018] [Accepted: 12/13/2018] [Indexed: 11/27/2022]
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40
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Czech B, Munafò M, Ciabrelli F, Eastwood EL, Fabry MH, Kneuss E, Hannon GJ. piRNA-Guided Genome Defense: From Biogenesis to Silencing. Annu Rev Genet 2018; 52:131-157. [PMID: 30476449 PMCID: PMC10784713 DOI: 10.1146/annurev-genet-120417-031441] [Citation(s) in RCA: 302] [Impact Index Per Article: 50.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
PIWI-interacting RNAs (piRNAs) and their associated PIWI clade Argonaute proteins constitute the core of the piRNA pathway. In gonadal cells, this conserved pathway is crucial for genome defense, and its main function is to silence transposable elements. This is achieved through posttranscriptional and transcriptional gene silencing. Precursors that give rise to piRNAs require specialized transcription and transport machineries because piRNA biogenesis is a cytoplasmic process. The ping-pong cycle, a posttranscriptional silencing mechanism, combines the cleavage-dependent silencing of transposon RNAs with piRNA production. PIWI proteins also function in the nucleus, where they scan for nascent target transcripts with sequence complementarity, instructing transcriptional silencing and deposition of repressive chromatin marks at transposon loci. Although studies have revealed numerous factors that participate in each branch of the piRNA pathway, the precise molecular roles of these factors often remain unclear. In this review, we summarize our current understanding of the mechanisms involved in piRNA biogenesis and function.
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Affiliation(s)
- Benjamin Czech
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, United Kingdom; ,
| | - Marzia Munafò
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, United Kingdom; ,
| | - Filippo Ciabrelli
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, United Kingdom; ,
| | - Evelyn L Eastwood
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, United Kingdom; ,
| | - Martin H Fabry
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, United Kingdom; ,
| | - Emma Kneuss
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, United Kingdom; ,
| | - Gregory J Hannon
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, United Kingdom; ,
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41
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Hug CB, Vaquerizas JM. The Birth of the 3D Genome during Early Embryonic Development. Trends Genet 2018; 34:903-914. [PMID: 30292539 DOI: 10.1016/j.tig.2018.09.002] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 08/23/2018] [Accepted: 09/06/2018] [Indexed: 12/15/2022]
Abstract
The 3D structure of chromatin in the nucleus is important for the regulation of gene expression and the correct deployment of developmental programs. The differentiation of germ cells and early embryonic development (when the zygotic genome is activated and transcription is taking place for the first time) are accompanied by dramatic changes in gene expression and the epigenetic landscape. Recent studies used Hi-C to investigate the 3D chromatin organization during these developmental transitions, uncovering remarkable remodeling of the 3D genome. Here, we highlight the changes described so far and discuss some of the implications that these findings have for our understanding of the mechanisms and functionality of 3D chromatin architecture.
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Affiliation(s)
- Clemens B Hug
- Max Planck Institute for Molecular Biomedicine, Roentgenstrasse 20, 48149 Muenster, Germany
| | - Juan M Vaquerizas
- Max Planck Institute for Molecular Biomedicine, Roentgenstrasse 20, 48149 Muenster, Germany. https://twitter.com/vaquerizasjm
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42
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Armstrong RL, Penke TJR, Strahl BD, Matera AG, McKay DJ, MacAlpine DM, Duronio RJ. Chromatin conformation and transcriptional activity are permissive regulators of DNA replication initiation in Drosophila. Genome Res 2018; 28:1688-1700. [PMID: 30279224 PMCID: PMC6211642 DOI: 10.1101/gr.239913.118] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Accepted: 09/24/2018] [Indexed: 12/19/2022]
Abstract
Chromatin structure has emerged as a key contributor to spatial and temporal control over the initiation of DNA replication. However, despite genome-wide correlations between early replication of gene-rich, accessible euchromatin and late replication of gene-poor, inaccessible heterochromatin, a causal relationship between chromatin structure and replication initiation remains elusive. Here, we combined histone gene engineering and whole-genome sequencing in Drosophila to determine how perturbing chromatin structure affects replication initiation. We found that most pericentric heterochromatin remains late replicating in H3K9R mutants, even though H3K9R pericentric heterochromatin is depleted of HP1a, more accessible, and transcriptionally active. These data indicate that HP1a loss, increased chromatin accessibility, and elevated transcription do not result in early replication of heterochromatin. Nevertheless, a small amount of pericentric heterochromatin with increased accessibility replicates earlier in H3K9R mutants. Transcription is de-repressed in these regions of advanced replication but not in those regions of the H3K9R mutant genome that replicate later, suggesting that transcriptional repression may contribute to late replication. We also explored relationships among chromatin, transcription, and replication in euchromatin by analyzing H4K16R mutants. In Drosophila, the X Chromosome gene expression is up-regulated twofold and replicates earlier in XY males than it does in XX females. We found that H4K16R mutation prevents normal male development and abrogates hyperexpression and earlier replication of the male X, consistent with previously established genome-wide correlations between transcription and early replication. In contrast, H4K16R females are viable and fertile, indicating that H4K16 modification is dispensable for genome replication and gene expression.
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Affiliation(s)
- Robin L Armstrong
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - Taylor J R Penke
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - Brian D Strahl
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.,Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599, USA.,Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - A Gregory Matera
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.,Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599, USA.,Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, North Carolina 27599, USA.,Department of Genetics.,Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - Daniel J McKay
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.,Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, North Carolina 27599, USA.,Department of Genetics.,Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - David M MacAlpine
- Department of Pharmacology and Cancer Biology, Duke University, Durham, North Carolina 27710, USA
| | - Robert J Duronio
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.,Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599, USA.,Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, North Carolina 27599, USA.,Department of Genetics.,Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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43
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Mutlu B, Chen HM, Moresco JJ, Orelo BD, Yang B, Gaspar JM, Keppler-Ross S, Yates JR, Hall DH, Maine EM, Mango SE. Regulated nuclear accumulation of a histone methyltransferase times the onset of heterochromatin formation in C. elegans embryos. SCIENCE ADVANCES 2018; 4:eaat6224. [PMID: 30140741 PMCID: PMC6105299 DOI: 10.1126/sciadv.aat6224] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2018] [Accepted: 07/18/2018] [Indexed: 05/19/2023]
Abstract
Heterochromatin formation during early embryogenesis is timed precisely, but how this process is regulated remains elusive. We report the discovery of a histone methyltransferase complex whose nuclear accumulation and activation establish the onset of heterochromatin formation in Caenorhabditis elegans embryos. We find that the inception of heterochromatin generation coincides with the accumulation of the histone H3 lysine 9 (H3K9) methyltransferase MET-2 (SETDB) into nuclear hubs. The absence of MET-2 results in delayed and disturbed heterochromatin formation, whereas accelerated nuclear localization of the methyltransferase leads to precocious H3K9 methylation. We identify two factors that bind to and function with MET-2: LIN-65, which resembles activating transcription factor 7-interacting protein (ATF7IP) and localizes MET-2 into nuclear hubs, and ARLE-14, which is orthologous to adenosine 5'-diphosphate-ribosylation factor-like 14 effector protein (ARL14EP) and promotes stable association of MET-2 with chromatin. These data reveal that nuclear accumulation of MET-2 in conjunction with LIN-65 and ARLE-14 regulates timing of heterochromatin domains during embryogenesis.
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Affiliation(s)
- Beste Mutlu
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
| | - Huei-Mei Chen
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
| | - James J. Moresco
- Department of Chemical Physiology, The Scripps Research Institute, La Jolla, San Diego, CA 92037, USA
| | - Barbara D. Orelo
- Department of Chemical Physiology, The Scripps Research Institute, La Jolla, San Diego, CA 92037, USA
| | - Bing Yang
- Department of Biology, Syracuse University, Syracuse, NY 13244, USA
| | - John M. Gaspar
- Informatics Group, Faculty of Arts and Sciences, Harvard University, Cambridge, MA 02138, USA
| | - Sabine Keppler-Ross
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
| | - John R. Yates
- Department of Chemical Physiology, The Scripps Research Institute, La Jolla, San Diego, CA 92037, USA
| | - David H. Hall
- Center for C. elegans Anatomy, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Eleanor M. Maine
- Department of Biology, Syracuse University, Syracuse, NY 13244, USA
| | - Susan E. Mango
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
- Corresponding author.
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44
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Seller CA, O’Farrell PH. Rif1 prolongs the embryonic S phase at the Drosophila mid-blastula transition. PLoS Biol 2018; 16:e2005687. [PMID: 29746464 PMCID: PMC5963817 DOI: 10.1371/journal.pbio.2005687] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 05/22/2018] [Accepted: 04/23/2018] [Indexed: 01/09/2023] Open
Abstract
In preparation for dramatic morphogenetic events of gastrulation, rapid embryonic cell cycles slow at the mid-blastula transition (MBT). In Drosophila melanogaster embryos, down-regulation of cyclin-dependent kinase 1 (Cdk1) activity initiates this slowing by delaying replication of heterochromatic satellite sequences and extending S phase. We found that Cdk1 activity inhibited the chromatin association of Rap1 interacting factor 1 (Rif1), a candidate repressor of replication. Furthermore, Rif1 bound selectively to satellite sequences following Cdk1 down-regulation at the MBT. In the next S phase, Rif1 dissociated from different satellites in an orderly schedule that anticipated their replication. Rif1 lacking potential phosphorylation sites failed to dissociate and dominantly prevented completion of replication. Loss of Rif1 in mutant embryos shortened the post-MBT S phase and rescued embryonic cell cycles disrupted by depletion of the S phase–promoting kinase, cell division cycle 7 (Cdc7). Our work shows that Rif1 and S phase kinases compose a replication timer controlling first the developmental onset of late replication and then the precise schedule of replication within S phase. In addition, we describe how onset of late replication fits into the progressive maturation of heterochromatin during development. Cells divide rapidly in the early embryos of most animals. However, during a conserved period of development known as the mid-blastula transition (MBT), the cell cycle slows down dramatically. In Drosophila embryos, genome duplication abruptly slows to initiate this cell cycle prolongation. This is achieved through the onset of late replication, a well-recognized phenomenon in which specific sequences of the genome await replication until long after other sequences have finished. Even though this temporal program of replication is a major determinant of the duration of S phase, the factors involved in this process remain unknown. Here, we use genetics and real-time microscopy to visualize replication in developing fly embryos and show that the protein Rap1 interacting factor 1 (Rif1) mediates the introduction of late replication at the MBT. We find that at this stage, Rif1 binds to and selectively delays the replication of large blocks of repetitive DNA known as satellite sequences. During the rapid cell cycles before the MBT, we show that the cyclin-dependent kinase 1 (Cdk1) prevents Rif1 from slowing down DNA replication by driving its removal from the chromatin. The developmental down-regulation of Cdk1 at the MBT allows Rif1 to associate with the satellite sequences and initiate cell cycle slowing. Our work provides new insights into the temporal programming of S phase and into the embryonic origin of late replication.
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Affiliation(s)
- Charles A. Seller
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, United States of America
| | - Patrick H. O’Farrell
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, United States of America
- * E-mail:
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45
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Abstract
The activation of the zygotic genome and onset of transcription in blastula embryos is linked to changes in cell behavior and remodeling of the cell cycle and constitutes a transition from exclusive maternal to zygotic control of development. This step in development is referred to as mid-blastula transition and has served as a paradigm for the link between developmental program and cell behavior and morphology. Here, we discuss the mechanism and functional relationships between the zygotic genome activation and cell cycle control during mid-blastula transition with a focus on Drosophila embryos.
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Affiliation(s)
- Boyang Liu
- Institute for Developmental Biochemistry, Medical School, University of Göttingen, Justus-von-Liebig-Weg11, Göttingen 37077, Germany
| | - Jörg Grosshans
- Institute for Developmental Biochemistry, Medical School, University of Göttingen, Justus-von-Liebig-Weg11, Göttingen 37077, Germany.
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46
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Strom AR, Emelyanov AV, Mir M, Fyodorov DV, Darzacq X, Karpen GH. Phase separation drives heterochromatin domain formation. Nature 2017; 547:241-245. [PMID: 28636597 PMCID: PMC6022742 DOI: 10.1038/nature22989] [Citation(s) in RCA: 1165] [Impact Index Per Article: 166.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Accepted: 05/31/2017] [Indexed: 12/13/2022]
Abstract
Constitutive heterochromatin is an important component of eukaryotic genomes that has essential roles in nuclear architecture, DNA repair and genome stability, and silencing of transposon and gene expression. Heterochromatin is highly enriched for repetitive sequences, and is defined epigenetically by methylation of histone H3 at lysine 9 and recruitment of its binding partner heterochromatin protein 1 (HP1). A prevalent view of heterochromatic silencing is that these and associated factors lead to chromatin compaction, resulting in steric exclusion of regulatory proteins such as RNA polymerase from the underlying DNA. However, compaction alone does not account for the formation of distinct, multi-chromosomal, membrane-less heterochromatin domains within the nucleus, fast diffusion of proteins inside the domain, and other dynamic features of heterochromatin. Here we present data that support an alternative hypothesis: that the formation of heterochromatin domains is mediated by phase separation, a phenomenon that gives rise to diverse non-membrane-bound nuclear, cytoplasmic and extracellular compartments. We show that Drosophila HP1a protein undergoes liquid-liquid demixing in vitro, and nucleates into foci that display liquid properties during the first stages of heterochromatin domain formation in early Drosophila embryos. Furthermore, in both Drosophila and mammalian cells, heterochromatin domains exhibit dynamics that are characteristic of liquid phase-separation, including sensitivity to the disruption of weak hydrophobic interactions, and reduced diffusion, increased coordinated movement and inert probe exclusion at the domain boundary. We conclude that heterochromatic domains form via phase separation, and mature into a structure that includes liquid and stable compartments. We propose that emergent biophysical properties associated with phase-separated systems are critical to understanding the unusual behaviours of heterochromatin, and how chromatin domains in general regulate essential nuclear functions.
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Affiliation(s)
- Amy R Strom
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
| | - Alexander V Emelyanov
- Albert Einstein College of Medicine, Department of Cell Biology, New York, New York, USA
| | - Mustafa Mir
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
| | - Dmitry V Fyodorov
- Albert Einstein College of Medicine, Department of Cell Biology, New York, New York, USA
| | - Xavier Darzacq
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
| | - Gary H Karpen
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
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Lee YCG, Karpen GH. Pervasive epigenetic effects of Drosophila euchromatic transposable elements impact their evolution. eLife 2017; 6. [PMID: 28695823 PMCID: PMC5505702 DOI: 10.7554/elife.25762] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Accepted: 06/09/2017] [Indexed: 12/21/2022] Open
Abstract
Transposable elements (TEs) are widespread genomic parasites, and their evolution has remained a critical question in evolutionary genomics. Here, we study the relatively unexplored epigenetic impacts of TEs and provide the first genome-wide quantification of such effects in D. melanogaster and D. simulans. Surprisingly, the spread of repressive epigenetic marks (histone H3K9me2) to nearby DNA occurs at >50% of euchromatic TEs, and can extend up to 20 kb. This results in differential epigenetic states of genic alleles and, in turn, selection against TEs. Interestingly, the lower TE content in D. simulans compared to D. melanogaster correlates with stronger epigenetic effects of TEs and higher levels of host genetic factors known to promote epigenetic silencing. Our study demonstrates that the epigenetic effects of euchromatic TEs, and host genetic factors modulating such effects, play a critical role in the evolution of TEs both within and between species. DOI:http://dx.doi.org/10.7554/eLife.25762.001 The DNA inside an organism encodes all the instructions needed for the organism to develop and work properly. Organisms carefully organize and maintain their DNA (collectively known as the genome) so that the genetic information remains intact and the cell can understand the instructions. However, there are some pieces of DNA that are capable of moving around the genome. For example, pieces known as transposable elements can make new copies of themselves and jump into new locations in the genome. Most transposons do not appear to have any important roles, and in fact they are usually harmful to organisms. Despite this, transposons are present in the genomes of almost all species. The number of transposons in a genome varies greatly between individuals and species, but it is not clear why this is the case. Organisms have evolved ways to limit the damage caused by transposons. For example, many cells package regions of DNA containing transposons into a tightly packed structure known as heterochromatin. However, this type of DNA packaging sometimes spreads to neighboring sections of DNA. This is a problem because cells are not usually able to read the information contained within heterochromatin. This means that transposons can prevent some instructions from being produced when they should be. Lee and Karpen used fruit flies to investigate to what extent transposons harm organisms by changing the way DNA is packaged, and whether this influences how transposons evolve. The experiments show that that more than half of the transposons in fruit flies cause neighboring sections of DNA to be packaged into heterochromatin. This can negatively impact up to 20% of genes in the genome. As a result, transposons that have harmful effects on DNA packaging are more likely to be lost from the fly population during evolution than transposons that do not have harmful effects. Fruit fly species containing transposons that tend to package more neighboring sections of DNA into heterochromatin generally have fewer transposons than genomes containing less harmful transposons. The findings of Lee and Karpen provide new insight as to why the numbers of transposons vary among organisms. The next challenge is to find out whether transposons that alter how DNA is packaged are also common in primates and other animals. DOI:http://dx.doi.org/10.7554/eLife.25762.002
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Affiliation(s)
- Yuh Chwen G Lee
- Division of Biological Systems and Engineering, Lawrence Berkeley National Laboratory, Berkeley, United States.,Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, United States
| | - Gary H Karpen
- Division of Biological Systems and Engineering, Lawrence Berkeley National Laboratory, Berkeley, United States.,Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, United States
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48
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Ren R, Deng L, Xue Y, Suzuki K, Zhang W, Yu Y, Wu J, Sun L, Gong X, Luan H, Yang F, Ju Z, Ren X, Wang S, Tang H, Geng L, Zhang W, Li J, Qiao J, Xu T, Qu J, Liu GH. Visualization of aging-associated chromatin alterations with an engineered TALE system. Cell Res 2017; 27:483-504. [PMID: 28139645 PMCID: PMC5385610 DOI: 10.1038/cr.2017.18] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Revised: 12/06/2016] [Accepted: 12/28/2016] [Indexed: 02/07/2023] Open
Abstract
Visualization of specific genomic loci in live cells is a prerequisite for the investigation of dynamic changes in chromatin architecture during diverse biological processes, such as cellular aging. However, current precision genomic imaging methods are hampered by the lack of fluorescent probes with high specificity and signal-to-noise contrast. We find that conventional transcription activator-like effectors (TALEs) tend to form protein aggregates, thereby compromising their performance in imaging applications. Through screening, we found that fusing thioredoxin with TALEs prevented aggregate formation, unlocking the full power of TALE-based genomic imaging. Using thioredoxin-fused TALEs (TTALEs), we achieved high-quality imaging at various genomic loci and observed aging-associated (epi) genomic alterations at telomeres and centromeres in human and mouse premature aging models. Importantly, we identified attrition of ribosomal DNA repeats as a molecular marker for human aging. Our study establishes a simple and robust imaging method for precisely monitoring chromatin dynamics in vitro and in vivo.
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Affiliation(s)
- Ruotong Ren
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Liping Deng
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Yanhong Xue
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Keiichiro Suzuki
- Gene Expression Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Weiqi Zhang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yang Yu
- Department of Gynecology and Obstetrics, Peking University Third Hospital, Beijing 100191, China
| | - Jun Wu
- Gene Expression Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Liang Sun
- The MOH Key Laboratory of Geriatrics, Beijing Hospital, National Center of Gerontology, Beijing 100730, China
| | - Xiaojun Gong
- Department of Pediatrics, Beijing Shijitan Hospital Capital Medical University, Peking University Ninth School of Clinical Medicine, Beijing 100038, China
| | - Huiqin Luan
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Fan Yang
- Key Laboratory of Regenerative Medicine of Ministry of Education, Institute of Aging and Regenerative Medicine, Jinan University, Guangzhou, Guangdong 510632, China
| | - Zhenyu Ju
- Institute of Aging Research, Hangzhou Normal University School of Medicine, Hangzhou, Zhejiang 311121, China
| | - Xiaoqing Ren
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Si Wang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Hong Tang
- Department of Pediatrics, Beijing Shijitan Hospital Capital Medical University, Peking University Ninth School of Clinical Medicine, Beijing 100038, China
| | - Lingling Geng
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Weizhou Zhang
- Department of Pathology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Jian Li
- The MOH Key Laboratory of Geriatrics, Beijing Hospital, National Center of Gerontology, Beijing 100730, China
| | - Jie Qiao
- Department of Gynecology and Obstetrics, Peking University Third Hospital, Beijing 100191, China
| | - Tao Xu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jing Qu
- University of Chinese Academy of Sciences, Beijing 100049, China
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Guang-Hui Liu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- Key Laboratory of Regenerative Medicine of Ministry of Education, Institute of Aging and Regenerative Medicine, Jinan University, Guangzhou, Guangdong 510632, China
- Beijing Institute for Brain Disorders, Beijing 100069, China
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49
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Imaging Translational and Post-Translational Gene Regulatory Dynamics in Living Cells with Antibody-Based Probes. Trends Genet 2017; 33:322-335. [PMID: 28359585 DOI: 10.1016/j.tig.2017.02.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 02/25/2017] [Accepted: 02/28/2017] [Indexed: 12/17/2022]
Abstract
Antibody derivatives, such as antibody fragments (Fabs) and single-chain variable fragments (scFvs), are now being used to image traditionally hard-to-see protein subpopulations, including nascent polypeptides being translated and post-translationally modified proteins. This has allowed researchers to directly image and quantify, for the first time, translation initiation and elongation kinetics with single-transcript resolution and the temporal ordering and kinetics of post-translational histone and RNA polymerase II modifications. Here, we review these developments and discuss the strengths and weaknesses of live-cell imaging with antibody-based probes. Further development of these probes will increase their versatility and open new avenues of research for dissecting complex gene regulatory dynamics.
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50
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Penke TJR, McKay DJ, Strahl BD, Matera AG, Duronio RJ. Direct interrogation of the role of H3K9 in metazoan heterochromatin function. Genes Dev 2016; 30:1866-80. [PMID: 27566777 PMCID: PMC5024684 DOI: 10.1101/gad.286278.116] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 08/05/2016] [Indexed: 11/24/2022]
Abstract
A defining feature of heterochromatin is methylation of Lys9 of histone H3 (H3K9me), a binding site for heterochromatin protein 1 (HP1). Penke et al. generated and analyzed H3K9R mutant flies, separating the functions of H3K9 and nonhistone substrates of H3K9 methyltransferases. A defining feature of heterochromatin is methylation of Lys9 of histone H3 (H3K9me), a binding site for heterochromatin protein 1 (HP1). Although H3K9 methyltransferases and HP1 are necessary for proper heterochromatin structure, the specific contribution of H3K9 to heterochromatin function and animal development is unknown. Using our recently developed platform to engineer histone genes in Drosophila, we generated H3K9R mutant flies, separating the functions of H3K9 and nonhistone substrates of H3K9 methyltransferases. Nucleosome occupancy and HP1a binding at pericentromeric heterochromatin are markedly decreased in H3K9R mutants. Despite these changes in chromosome architecture, a small percentage of H3K9R mutants complete development. Consistent with this result, expression of most protein-coding genes, including those within heterochromatin, is similar between H3K9R and controls. In contrast, H3K9R mutants exhibit increased open chromatin and transcription from piRNA clusters and transposons, resulting in transposon mobilization. Hence, transposon silencing is a major developmental function of H3K9.
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Affiliation(s)
- Taylor J R Penke
- Curriculum in Genetics and Molecular Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Daniel J McKay
- Curriculum in Genetics and Molecular Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA; Integrative Program for Biological and Genome Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA; Department of Genetics, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA; Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Brian D Strahl
- Curriculum in Genetics and Molecular Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA; Department of Biochemistry and Biophysics, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA; Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - A Gregory Matera
- Curriculum in Genetics and Molecular Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA; Integrative Program for Biological and Genome Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA; Department of Genetics, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA; Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA; Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Robert J Duronio
- Curriculum in Genetics and Molecular Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA; Integrative Program for Biological and Genome Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA; Department of Genetics, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA; Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA; Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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