1
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Bai J, Lin Y, Zhang J, Chen Z, Wang Y, Li M, Li J. Profiling of Chromatin Accessibility in Pigs across Multiple Tissues and Developmental Stages. Int J Mol Sci 2023; 24:11076. [PMID: 37446255 DOI: 10.3390/ijms241311076] [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: 05/06/2023] [Revised: 06/27/2023] [Accepted: 06/30/2023] [Indexed: 07/15/2023] Open
Abstract
The study of chromatin accessibility across tissues and developmental stages is essential for elucidating the transcriptional regulation of various phenotypes and biological processes. However, the chromatin accessibility profiles of multiple tissues in newborn pigs and across porcine liver development remain poorly investigated. Here, we used ATAC-seq and rRNA-depleted RNA-seq to profile open chromatin maps and transcriptional features of heart, kidney, liver, lung, skeletal muscle, and spleen in newborn pigs and porcine liver tissue in the suckling and adult stages, respectively. Specifically, by analyzing a union set of protein-coding genes (PCGs) and two types of transcripts (lncRNAs and TUCPs), we obtained a comprehensive annotation of consensus ATAC-seq peaks for each tissue and developmental stage. As expected, the PCGs with tissue-specific accessible promoters had active transcription and were relevant to tissue-specific functions. In addition, other non-coding tissue-specific peaks were involved in both physical activity and the morphogenesis of neonatal tissues. We also characterized stage-specific peaks and observed a close association between dynamic chromatin accessibility and hepatic function transition during liver postnatal development. Overall, this study expands our current understanding of epigenetic regulation in mammalian tissues and organ development, which can benefit both economic trait improvement and improve the biomedical usage of pigs.
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Affiliation(s)
- Jingyi Bai
- Institute of Animal Genetics and Breeding, College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, China
| | - Yu Lin
- Institute of Animal Genetics and Breeding, College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, China
| | - Jiaman Zhang
- Institute of Animal Genetics and Breeding, College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, China
| | - Ziyu Chen
- Institute of Animal Genetics and Breeding, College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, China
| | - Yujie Wang
- Institute of Animal Genetics and Breeding, College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, China
| | - Mingzhou Li
- Institute of Animal Genetics and Breeding, College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, China
| | - Jing Li
- Institute of Animal Genetics and Breeding, College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, China
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2
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Nucleosome-directed replication origin licensing independent of a consensus DNA sequence. Nat Commun 2022; 13:4947. [PMID: 35999198 PMCID: PMC9399094 DOI: 10.1038/s41467-022-32657-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Accepted: 08/09/2022] [Indexed: 02/08/2023] Open
Abstract
The numerous enzymes and cofactors involved in eukaryotic DNA replication are conserved from yeast to human, and the budding yeast Saccharomyces cerevisiae (S.c.) has been a useful model organism for these studies. However, there is a gap in our knowledge of why replication origins in higher eukaryotes do not use a consensus DNA sequence as found in S.c. Using in vitro reconstitution and single-molecule visualization, we show here that S.c. origin recognition complex (ORC) stably binds nucleosomes and that ORC-nucleosome complexes have the intrinsic ability to load the replicative helicase MCM double hexamers onto adjacent nucleosome-free DNA regardless of sequence. Furthermore, we find that Xenopus laevis nucleosomes can substitute for yeast ones in engaging with ORC. Combined with re-analyses of genome-wide ORC binding data, our results lead us to propose that the yeast origin recognition machinery contains the cryptic capacity to bind nucleosomes near a nucleosome-free region and license origins, and that this nucleosome-directed origin licensing paradigm generalizes to all eukaryotes. Most eukaryotes do not use a consensus DNA sequence as binding sites for the origin recognition complex (ORC) to initiate DNA replication, however budding yeast do. Here the authors show S. cerevisiae ORC can bind nucleosomes near nucleosome-free regions and recruit replicative helicases to form a pre-replication complex independent of the DNA sequence.
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3
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Ahmad SS, Samia NSN, Khan AS, Turjya RR, Khan MAAK. Bidirectional promoters: an enigmatic genome architecture and their roles in cancers. Mol Biol Rep 2021; 48:6637-6644. [PMID: 34378109 DOI: 10.1007/s11033-021-06612-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Accepted: 07/29/2021] [Indexed: 11/28/2022]
Abstract
Bidirectional promoters are the transcription regulatory regions of genes positioned head-to-head on opposite strands. Specific sequence signals, chromatin modifications and three-dimensional structures of the transcription site facilitate the unconventional yet tightly regulated transcription proceeding in both directions from these promoters. Mutations or aberrant epigenetic changes can lead to abnormal enhanced or reduced expression from either of the bidirectionally transcribed genes resulting in tumorigenesis. Moreover, bidirectionally transcribed genes might also contribute towards the immune regulation in tumor microenvironment. In this review, we aimed to expound the characteristic features of bidirectional promoters alongside their transcriptional regulations, and ultimately, the association of these enigmatic genomic elements in different cancers.
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Affiliation(s)
- Sheikh Shafin Ahmad
- Department of Mathematics and Natural Sciences, Brac University, Dhaka, Bangladesh
| | | | - Auroni Semonti Khan
- Department of Genetic Engineering and Biotechnology, Jagannath University, Dhaka, Bangladesh
| | - Rafeed Rahman Turjya
- Department of Mathematics and Natural Sciences, Brac University, Dhaka, Bangladesh
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4
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Clapier CR. Sophisticated Conversations between Chromatin and Chromatin Remodelers, and Dissonances in Cancer. Int J Mol Sci 2021; 22:5578. [PMID: 34070411 PMCID: PMC8197500 DOI: 10.3390/ijms22115578] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 05/18/2021] [Accepted: 05/18/2021] [Indexed: 01/13/2023] Open
Abstract
The establishment and maintenance of genome packaging into chromatin contribute to define specific cellular identity and function. Dynamic regulation of chromatin organization and nucleosome positioning are critical to all DNA transactions-in particular, the regulation of gene expression-and involve the cooperative action of sequence-specific DNA-binding factors, histone modifying enzymes, and remodelers. Remodelers are molecular machines that generate various chromatin landscapes, adjust nucleosome positioning, and alter DNA accessibility by using ATP binding and hydrolysis to perform DNA translocation, which is highly regulated through sophisticated structural and functional conversations with nucleosomes. In this review, I first present the functional and structural diversity of remodelers, while emphasizing the basic mechanism of DNA translocation, the common regulatory aspects, and the hand-in-hand progressive increase in complexity of the regulatory conversations between remodelers and nucleosomes that accompanies the increase in challenges of remodeling processes. Next, I examine how, through nucleosome positioning, remodelers guide the regulation of gene expression. Finally, I explore various aspects of how alterations/mutations in remodelers introduce dissonance into the conversations between remodelers and nucleosomes, modify chromatin organization, and contribute to oncogenesis.
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Affiliation(s)
- Cedric R Clapier
- Department of Oncological Sciences & Howard Hughes Medical Institute, Huntsman Cancer Institute, University of Utah School of Medicine, 2000 Circle of Hope, Salt Lake City, UT 84112, USA
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5
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Kharerin H, Bai L. Thermodynamic modeling of genome-wide nucleosome depleted regions in yeast. PLoS Comput Biol 2021; 17:e1008560. [PMID: 33428627 PMCID: PMC7822557 DOI: 10.1371/journal.pcbi.1008560] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Revised: 01/22/2021] [Accepted: 11/25/2020] [Indexed: 01/09/2023] Open
Abstract
Nucleosome positioning in the genome is essential for the regulation of many nuclear processes. We currently have limited capability to predict nucleosome positioning in vivo, especially the locations and sizes of nucleosome depleted regions (NDRs). Here, we present a thermodynamic model that incorporates the intrinsic affinity of histones, competitive binding of sequence-specific factors, and nucleosome remodeling to predict nucleosome positioning in budding yeast. The model shows that the intrinsic affinity of histones, at near-saturating histone concentration, is not sufficient in generating NDRs in the genome. However, the binding of a few factors, especially RSC towards GC-rich and poly(A/T) sequences, allows us to predict ~ 66% of genome-wide NDRs. The model also shows that nucleosome remodeling activity is required to predict the correct NDR sizes. The validity of the model was further supported by the agreement between the predicted and the measured nucleosome positioning upon factor deletion or on exogenous sequences introduced into yeast. Overall, our model quantitatively evaluated the impact of different genetic components on NDR formation and illustrated the vital roles of sequence-specific factors and nucleosome remodeling in this process. Nucleosome is the basic unit of chromatin, containing 147 base-pairs of DNA wrapped around a histone core. The positioning of nucleosomes, i.e., which parts of DNA are inside nucleosome and which parts are nucleosome-free, is highly regulated. In particular, regulatory sequences tend to be exposed in nucleosome-depleted regions (NDRs), and such exposure is crucial for a variety of processes including DNA replication, repair, and gene expression. Here, we used a thermodynamics model to predict nucleosome positioning on the yeast genome. The model shows that the intrinsic sequence preference of histones is not sufficient in generating NDRs. In contrast, binding of a few transcription factors, especially RSC, is largely responsible for NDR formation. Nucleosome remodeling activity is also required in the model to recapitulate the NDR sizes. This model contributes to our understanding of the mechanisms that regulate nucleosome positioning. It can also be used to predict nucleosome positioning in mutant yeast or on novel DNA sequences.
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Affiliation(s)
- Hungyo Kharerin
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- Center for Eukaryotic Gene Regulation, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Lu Bai
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- Center for Eukaryotic Gene Regulation, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- * E-mail:
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6
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Schüller A, Wolansky L, Berger H, Studt L, Gacek-Matthews A, Sulyok M, Strauss J. A novel fungal gene regulation system based on inducible VPR-dCas9 and nucleosome map-guided sgRNA positioning. Appl Microbiol Biotechnol 2020; 104:9801-9822. [PMID: 33006690 PMCID: PMC7595996 DOI: 10.1007/s00253-020-10900-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 08/31/2020] [Accepted: 09/08/2020] [Indexed: 12/16/2022]
Abstract
Programmable transcriptional regulation is a powerful tool to study gene functions. Current methods to selectively regulate target genes are mainly based on promoter exchange or on overexpressing transcriptional activators. To expand the discovery toolbox, we designed a dCas9-based RNA-guided synthetic transcription activation system for Aspergillus nidulans that uses enzymatically disabled "dead" Cas9 fused to three consecutive activation domains (VPR-dCas9). The dCas9-encoding gene is under the control of an estrogen-responsive promoter to allow induction timing and to avoid possible negative effects by strong constitutive expression of the highly active VPR domains. Especially in silent genomic regions, facultative heterochromatin and strictly positioned nucleosomes can constitute a relevant obstacle to the transcriptional machinery. To avoid this negative impact and to facilitate optimal positioning of RNA-guided VPR-dCas9 to targeted promoters, we have created a genome-wide nucleosome map from actively growing cells and stationary cultures to identify the cognate nucleosome-free regions (NFRs). Based on these maps, different single-guide RNAs (sgRNAs) were designed and tested for their targeting and activation potential. Our results demonstrate that the system can be used to regulate several genes in parallel and, depending on the VPR-dCas9 positioning, expression can be pushed to very high levels. We have used the system to turn on individual genes within two different biosynthetic gene clusters (BGCs) which are silent under normal growth conditions. This method also opens opportunities to stepwise activate individual genes in a cluster to decipher the correlated biosynthetic pathway. Graphical abstract KEYPOINTS: • An inducible RNA-guided transcriptional regulator based on VPR-dCas9 was established in Aspergillus nidulans. • Genome-wide nucleosome positioning maps were created that facilitate sgRNA positioning. • The system was successfully applied to activate genes within two silent biosynthetic gene clusters.
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Affiliation(s)
- Andreas Schüller
- Fungal Genetics Lab, Institute of Microbial Genetics, Department of Applied Genetics and Cell Biology, BOKU-University of Natural Resources and Life Sciences Vienna, BOKU-Campus Tulln, Konrad Lorenz Strasse 24, A-3430, Tulln an der Donau, Austria
| | - Lisa Wolansky
- Institute Krems Bioanalytics , IMC FH Krems University of Applied Sciences , Krems, Austria
| | - Harald Berger
- Fungal Genetics Lab, Institute of Microbial Genetics, Department of Applied Genetics and Cell Biology, BOKU-University of Natural Resources and Life Sciences Vienna, BOKU-Campus Tulln, Konrad Lorenz Strasse 24, A-3430, Tulln an der Donau, Austria
| | - Lena Studt
- Fungal Genetics Lab, Institute of Microbial Genetics, Department of Applied Genetics and Cell Biology, BOKU-University of Natural Resources and Life Sciences Vienna, BOKU-Campus Tulln, Konrad Lorenz Strasse 24, A-3430, Tulln an der Donau, Austria
| | - Agnieszka Gacek-Matthews
- Fungal Genetics Lab, Institute of Microbial Genetics, Department of Applied Genetics and Cell Biology, BOKU-University of Natural Resources and Life Sciences Vienna, BOKU-Campus Tulln, Konrad Lorenz Strasse 24, A-3430, Tulln an der Donau, Austria
- Institute of Microbiology, Functional Microbiology Division, University of Veterinary Sciences Vienna, Wien, Austria
| | - Michael Sulyok
- Institute of Bioanalytics and Agrometabolomics, Department of Agrobiotechnology, BOKU-University of Natural Resources and Life Sciences Vienna, BOKU-Campus Tulln, Konrad-Lorenz-Straße 20, A-3430 Tulln an der Donau, Austria
| | - Joseph Strauss
- Fungal Genetics Lab, Institute of Microbial Genetics, Department of Applied Genetics and Cell Biology, BOKU-University of Natural Resources and Life Sciences Vienna, BOKU-Campus Tulln, Konrad Lorenz Strasse 24, A-3430, Tulln an der Donau, Austria.
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7
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Palazzo AF, Koonin EV. Functional Long Non-coding RNAs Evolve from Junk Transcripts. Cell 2020; 183:1151-1161. [PMID: 33068526 DOI: 10.1016/j.cell.2020.09.047] [Citation(s) in RCA: 128] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 08/20/2020] [Accepted: 09/17/2020] [Indexed: 12/30/2022]
Abstract
Transcriptome studies reveal pervasive transcription of complex genomes, such as those of mammals. Despite popular arguments for functionality of most, if not all, of these transcripts, genome-wide analysis of selective constraints indicates that most of the produced RNA are junk. However, junk is not garbage. On the contrary, junk transcripts provide the raw material for the evolution of diverse long non-coding (lnc) RNAs by non-adaptive mechanisms, such as constructive neutral evolution. The generation of many novel functional entities, such as lncRNAs, that fuels organismal complexity does not seem to be driven by strong positive selection. Rather, the weak selection regime that dominates the evolution of most multicellular eukaryotes provides ample material for functional innovation with relatively little adaptation involved.
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Affiliation(s)
- Alexander F Palazzo
- Department of Biochemistry, University of Toronto, Toronto, ON M5G 1M1, Canada.
| | - Eugene V Koonin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA.
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8
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Singh A, Choudhuri P, Chandradoss KR, Lal M, Mishra SK, Sandhu KS. Does genome surveillance explain the global discrepancy between binding and effect of chromatin factors? FEBS Lett 2020; 594:1339-1353. [PMID: 31930486 DOI: 10.1002/1873-3468.13729] [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: 09/17/2019] [Revised: 12/16/2019] [Accepted: 12/19/2019] [Indexed: 11/11/2022]
Abstract
Knocking out a chromatin factor often does not alter the transcription of its binding targets. What explains the observed disconnect between binding and effect? We hypothesize that this discrepancy could be associated with the role of chromatin factors in maintaining genetic and epigenetic integrity at promoters, and not necessarily with transcription. Through re-analysis of published datasets, we present several lines of evidence that support our hypothesis and deflate the popular assumptions. We also tested the hypothesis through mutation accumulation assays on yeast knockouts of chromatin factors. Altogether, the proposed hypothesis presents a simple explanation for the global discord between chromatin factor binding and effect. Future work in this direction might fortify the hypothesis and elucidate the underlying mechanisms.
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Affiliation(s)
- Arashdeep Singh
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER)-Mohali, India
| | - Poulami Choudhuri
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER)-Mohali, India
| | | | - Mohan Lal
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER)-Mohali, India
| | - Shravan Kumar Mishra
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER)-Mohali, India
| | - Kuljeet Singh Sandhu
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER)-Mohali, India
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9
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Kubik S, Bruzzone MJ, Challal D, Dreos R, Mattarocci S, Bucher P, Libri D, Shore D. Opposing chromatin remodelers control transcription initiation frequency and start site selection. Nat Struct Mol Biol 2019; 26:744-754. [PMID: 31384063 DOI: 10.1038/s41594-019-0273-3] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 06/28/2019] [Indexed: 12/31/2022]
Abstract
Precise nucleosome organization at eukaryotic promoters is thought to be generated by multiple chromatin remodeler (CR) enzymes and to affect transcription initiation. Using an integrated analysis of chromatin remodeler binding and nucleosome occupancy following rapid remodeler depletion, we investigated the interplay between these enzymes and their impact on transcription in yeast. We show that many promoters are affected by multiple CRs that operate in concert or in opposition to position the key transcription start site (TSS)-associated +1 nucleosome. We also show that nucleosome movement after CR inactivation usually results from the activity of another CR and that in the absence of any remodeling activity, +1 nucleosomes largely maintain their positions. Finally, we present functional assays suggesting that +1 nucleosome positioning often reflects a trade-off between maximizing RNA polymerase recruitment and minimizing transcription initiation at incorrect sites. Our results provide a detailed picture of fundamental mechanisms linking promoter nucleosome architecture to transcription initiation.
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Affiliation(s)
- Slawomir Kubik
- Department of Molecular Biology and Institute of Genetics and Genomics of Geneva (iGE3), Geneva, Switzerland
| | - Maria Jessica Bruzzone
- Department of Molecular Biology and Institute of Genetics and Genomics of Geneva (iGE3), Geneva, Switzerland
| | - Drice Challal
- Institut Jacques Monod, CNRS-Université Paris Diderot, Paris, France
| | - René Dreos
- Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Stefano Mattarocci
- Department of Molecular Biology and Institute of Genetics and Genomics of Geneva (iGE3), Geneva, Switzerland
| | - Philipp Bucher
- Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Domenico Libri
- Institut Jacques Monod, CNRS-Université Paris Diderot, Paris, France
| | - David Shore
- Department of Molecular Biology and Institute of Genetics and Genomics of Geneva (iGE3), Geneva, Switzerland.
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10
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Parnell EJ, Stillman DJ. Multiple Negative Regulators Restrict Recruitment of the SWI/SNF Chromatin Remodeler to the HO Promoter in Saccharomyces cerevisiae. Genetics 2019; 212:1181-1204. [PMID: 31167839 PMCID: PMC6707452 DOI: 10.1534/genetics.119.302359] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Accepted: 05/30/2019] [Indexed: 01/22/2023] Open
Abstract
Activation of the Saccharomyces cerevisiae HO promoter is highly regulated, requiring the ordered recruitment of activators and coactivators and allowing production of only a few transcripts in mother cells within a short cell cycle window. We conducted genetic screens to identify the negative regulators of HO expression necessary to limit HO transcription. Known repressors of HO (Ash1 and Rpd3) were identified, as well as several additional chromatin-associated factors including the Hda1 histone deacetylase, the Isw2 chromatin remodeler, and the corepressor Tup1 We also identified clusters of HO promoter mutations that suggested roles for the Dot6/Tod6 (PAC site) and Ume6 repression pathways. We used ChIP assays with synchronized cells to validate the involvement of these factors and map the association of Ash1, Dot6, and Ume6 with the HO promoter to a brief window in the cell cycle between binding of the initial activating transcription factor and initiation of transcription. We found that Ash1 and Ume6 each recruit the Rpd3 histone deacetylase to HO, and their effects are additive. In contrast, Rpd3 was not recruited significantly to the PAC site, suggesting this site has a distinct mechanism for repression. Increases in HO expression and SWI/SNF recruitment were all additive upon loss of Ash1, Ume6, and PAC site factors, indicating the convergence of independent pathways for repression. Our results demonstrate that multiple protein complexes are important for limiting the spread of SWI/SNF-mediated nucleosome eviction across the HO promoter, suggesting that regulation requires a delicate balance of activities that promote and repress transcription.
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Affiliation(s)
- Emily J Parnell
- Department of Pathology, University of Utah Health Sciences Center, Salt Lake City, Utah 84112
| | - David J Stillman
- Department of Pathology, University of Utah Health Sciences Center, Salt Lake City, Utah 84112
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11
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van Eijk P, Nandi SP, Yu S, Bennett M, Leadbitter M, Teng Y, Reed SH. Nucleosome remodeling at origins of global genome-nucleotide excision repair occurs at the boundaries of higher-order chromatin structure. Genome Res 2018; 29:74-84. [PMID: 30552104 PMCID: PMC6314166 DOI: 10.1101/gr.237198.118] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 11/07/2018] [Indexed: 11/24/2022]
Abstract
Repair of UV-induced DNA damage requires chromatin remodeling. How repair is initiated in chromatin remains largely unknown. We recently demonstrated that global genome–nucleotide excision repair (GG-NER) in chromatin is organized into domains in relation to open reading frames. Here, we define these domains, identifying the genomic locations from which repair is initiated. By examining DNA damage–induced changes in the linear structure of nucleosomes at these sites, we demonstrate how chromatin remodeling is initiated during GG-NER. In undamaged cells, we show that the GG-NER complex occupies chromatin, establishing the nucleosome structure at these genomic locations, which we refer to as GG-NER complex binding sites (GCBSs). We demonstrate that these sites are frequently located at genomic boundaries that delineate chromosomally interacting domains (CIDs). These boundaries define domains of higher-order nucleosome–nucleosome interaction. We demonstrate that initiation of GG-NER in chromatin is accompanied by the disruption of dynamic nucleosomes that flank GCBSs by the GG-NER complex.
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Affiliation(s)
- Patrick van Eijk
- Institute of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff CF14 4XN, United Kingdom
| | - Shuvro Prokash Nandi
- Institute of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff CF14 4XN, United Kingdom
| | - Shirong Yu
- Institute of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff CF14 4XN, United Kingdom
| | - Mark Bennett
- Institute of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff CF14 4XN, United Kingdom
| | - Matthew Leadbitter
- Institute of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff CF14 4XN, United Kingdom
| | - Yumin Teng
- Institute of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff CF14 4XN, United Kingdom
| | - Simon H Reed
- Institute of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff CF14 4XN, United Kingdom
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12
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Azofeifa JG, Allen MA, Hendrix JR, Read T, Rubin JD, Dowell RD. Enhancer RNA profiling predicts transcription factor activity. Genome Res 2018; 28:334-344. [PMID: 29449408 PMCID: PMC5848612 DOI: 10.1101/gr.225755.117] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Accepted: 01/24/2018] [Indexed: 12/18/2022]
Abstract
Transcription factors (TFs) exert their regulatory influence through the binding of enhancers, resulting in coordination of gene expression programs. Active enhancers are often characterized by the presence of short, unstable transcripts termed enhancer RNAs (eRNAs). While their function remains unclear, we demonstrate that eRNAs are a powerful readout of TF activity. We infer sites of eRNA origination across hundreds of publicly available nascent transcription data sets and show that eRNAs initiate from sites of TF binding. By quantifying the colocalization of TF binding motif instances and eRNA origins, we derive a simple statistic capable of inferring TF activity. In doing so, we uncover dozens of previously unexplored links between diverse stimuli and the TFs they affect.
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Affiliation(s)
- Joseph G Azofeifa
- Department of Computer Science, University of Colorado, Boulder, Colorado 80309, USA
- BioFrontiers Institute, University of Colorado, Boulder, Colorado 80309, USA
| | - Mary A Allen
- BioFrontiers Institute, University of Colorado, Boulder, Colorado 80309, USA
| | - Josephina R Hendrix
- Department of Computer Science, University of Colorado, Boulder, Colorado 80309, USA
- Department of Molecular, Cellular and Developmental Biology
| | - Timothy Read
- BioFrontiers Institute, University of Colorado, Boulder, Colorado 80309, USA
- Department of Biochemistry, University of Colorado, Boulder, Colorado 80309, USA
| | - Jonathan D Rubin
- Department of Biochemistry, University of Colorado, Boulder, Colorado 80309, USA
| | - Robin D Dowell
- Department of Computer Science, University of Colorado, Boulder, Colorado 80309, USA
- BioFrontiers Institute, University of Colorado, Boulder, Colorado 80309, USA
- Department of Molecular, Cellular and Developmental Biology
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13
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Emerging mechanisms of long noncoding RNA function during normal and malignant hematopoiesis. Blood 2017; 130:1965-1975. [PMID: 28928124 DOI: 10.1182/blood-2017-06-788695] [Citation(s) in RCA: 121] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Accepted: 09/15/2017] [Indexed: 12/22/2022] Open
Abstract
Long noncoding RNAs (lncRNAs) are increasingly recognized as vital components of gene programs controlling cell differentiation and function. Central to their functions is an ability to act as scaffolds or as decoys that recruit or sequester effector proteins from their DNA, RNA, or protein targets. lncRNA-modulated effectors include regulators of transcription, chromatin organization, RNA processing, and translation, such that lncRNAs can influence gene expression at multiple levels. Here we review the current understanding of how lncRNAs help coordinate gene expression to modulate cell fate in the hematopoietic system. We focus on a growing number of mechanistic studies to synthesize emerging principles of lncRNA function, emphasizing how they facilitate diversification of gene programming during development. We also survey how disrupted lncRNA function can contribute to malignant transformation, highlighting opportunities for therapeutic intervention in specific myeloid and lymphoid cancers. Finally, we discuss challenges and prospects for further elucidation of lncRNA mechanisms.
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14
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Bowman GD, McKnight JN. Sequence-specific targeting of chromatin remodelers organizes precisely positioned nucleosomes throughout the genome. Bioessays 2016; 39:1-8. [PMID: 27862071 DOI: 10.1002/bies.201600183] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Eukaryotic genomes are functionally organized into chromatin, a compact packaging of nucleoproteins with the basic repeating unit known as the nucleosome. A major focus for the chromatin field has been understanding what rules govern nucleosome positioning throughout the genome, and here we review recent findings using a novel, sequence-targeted remodeling enzyme. Nucleosomes are often packed into evenly spaced arrays that are reproducibly positioned, but how such organization is established and maintained through dramatic events such as DNA replication is poorly understood. We hypothesize that a major fraction of positioned nucleosomes arises from sequence-specific targeting of chromatin remodelers to generate "founding" nucleosomes, providing reproducible, predictable, and condition-specific nucleation sites against which neighboring nucleosomes are packed into evenly spaced arrays.
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Affiliation(s)
- Gregory D Bowman
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD, USA
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15
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Al-Hadid Q, Yang Y. R-loop: an emerging regulator of chromatin dynamics. Acta Biochim Biophys Sin (Shanghai) 2016; 48:623-31. [PMID: 27252122 DOI: 10.1093/abbs/gmw052] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2016] [Accepted: 04/29/2016] [Indexed: 12/27/2022] Open
Abstract
The dynamic structure of chromatin, which exists in two conformational states: heterochromatin and euchromatin, alters the accessibility of the DNA to regulatory factors during transcription, replication, recombination, and DNA damage repair. Chemical modifications of histones and DNA, as well as adenosine triphospahate-dependent nucleosome remodeling, have been the major focus of research on chromatin dynamics over the past two decades. However, recent studies using a DNA-RNA hybrid-specific antibody and next-generation sequencing approaches have revealed that the formation of R-loops, one of the most common non-canonical DNA structures, is an emerging regulator of chromatin states. This review focuses on recent insights into the interplay between R-loop formation and the epigenetic modifications of chromatin in normal and disease states.
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Affiliation(s)
- Qais Al-Hadid
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope Cancer Center, Duarte, CA 91010, USA
| | - Yanzhong Yang
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope Cancer Center, Duarte, CA 91010, USA
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16
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Mostovoy Y, Thiemicke A, Hsu TY, Brem RB. The Role of Transcription Factors at Antisense-Expressing Gene Pairs in Yeast. Genome Biol Evol 2016; 8:1748-61. [PMID: 27190003 PMCID: PMC4943177 DOI: 10.1093/gbe/evw104] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Genes encoded close to one another on the chromosome are often coexpressed, by a mechanism and regulatory logic that remain poorly understood. We surveyed the yeast genome for tandem gene pairs oriented tail-to-head at which expression antisense to the upstream gene was conserved across species. The intergenic region at most such tandem pairs is a bidirectional promoter, shared by the downstream gene mRNA and the upstream antisense transcript. Genomic analyses of these intergenic loci revealed distinctive patterns of transcription factor regulation. Mutation of a given transcription factor verified its role as a regulator in trans of tandem gene pair loci, including the proximally initiating upstream antisense transcript and downstream mRNA and the distally initiating upstream mRNA. To investigate cis-regulatory activity at such a locus, we focused on the stress-induced NAD(P)H dehydratase YKL151C and its downstream neighbor, the metabolic enzyme GPM1. Previous work has implicated the region between these genes in regulation of GPM1 expression; our mutation experiments established its function in rich medium as a repressor in cis of the distally initiating YKL151C sense RNA, and an activator of the proximally initiating YKL151C antisense RNA. Wild-type expression of all three transcripts required the transcription factor Gcr2. Thus, at this locus, the intergenic region serves as a focal point of regulatory input, driving antisense expression and mediating the coordinated regulation of YKL151C and GPM1. Together, our findings implicate transcription factors in the joint control of neighboring genes specialized to opposing conditions and the antisense transcripts expressed between them.
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Affiliation(s)
- Yulia Mostovoy
- Department of Molecular and Cell Biology, University of California, Berkeley, California Present address: Cardiovascular Research Institute, University of California, San Francisco, CA
| | - Alexander Thiemicke
- Department of Molecular and Cell Biology, University of California, Berkeley, California Program in Molecular Medicine, Friedrich-Schiller-Universität, Jena, Germany Present address: Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN
| | - Tiffany Y Hsu
- Department of Molecular and Cell Biology, University of California, Berkeley, California Present address: Graduate Program in Biological and Biomedical Sciences, Harvard Medical School, Boston, MA
| | - Rachel B Brem
- Department of Molecular and Cell Biology, University of California, Berkeley, California Present address: Buck Institute for Research on Aging, Novato, CA
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McKnight JN, Tsukiyama T, Bowman GD. Sequence-targeted nucleosome sliding in vivo by a hybrid Chd1 chromatin remodeler. Genome Res 2016; 26:693-704. [PMID: 26993344 PMCID: PMC4864466 DOI: 10.1101/gr.199919.115] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2015] [Accepted: 03/14/2016] [Indexed: 01/15/2023]
Abstract
ATP-dependent chromatin remodelers regulate chromatin dynamics by modifying nucleosome positions and occupancy. DNA-dependent processes such as replication and transcription rely on chromatin to faithfully regulate DNA accessibility, yet how chromatin remodelers achieve well-defined nucleosome positioning in vivo is poorly understood. Here, we report a simple method for site-specifically altering nucleosome positions in live cells. By fusing the Chd1 remodeler to the DNA binding domain of the Saccharomyces cerevisiae Ume6 repressor, we have engineered a fusion remodeler that selectively positions nucleosomes on top of adjacent Ume6 binding motifs in a highly predictable and reproducible manner. Positioning of nucleosomes by the fusion remodeler recapitulates closed chromatin structure at Ume6-sensitive genes analogous to the endogenous Isw2 remodeler. Strikingly, highly precise positioning of single founder nucleosomes by either chimeric Chd1-Ume6 or endogenous Isw2 shifts phased chromatin arrays in cooperation with endogenous chromatin remodelers. Our results demonstrate feasibility of engineering precise nucleosome rearrangements through sequence-targeted chromatin remodeling and provide insight into targeted action and cooperation of endogenous chromatin remodelers in vivo.
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Affiliation(s)
- Jeffrey N McKnight
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
| | - Toshio Tsukiyama
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
| | - Gregory D Bowman
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland 21218, USA
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18
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Hildebrand EM, Biggins S. Regulation of Budding Yeast CENP-A levels Prevents Misincorporation at Promoter Nucleosomes and Transcriptional Defects. PLoS Genet 2016; 12:e1005930. [PMID: 26982580 PMCID: PMC4794243 DOI: 10.1371/journal.pgen.1005930] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 02/22/2016] [Indexed: 01/08/2023] Open
Abstract
The exclusive localization of the histone H3 variant CENP-A to centromeres is essential for accurate chromosome segregation. Ubiquitin-mediated proteolysis helps to ensure that CENP-A does not mislocalize to euchromatin, which can lead to genomic instability. Consistent with this, overexpression of the budding yeast CENP-ACse4 is lethal in cells lacking Psh1, the E3 ubiquitin ligase that targets CENP-ACse4 for degradation. To identify additional mechanisms that prevent CENP-ACse4 misincorporation and lethality, we analyzed the genome-wide mislocalization pattern of overexpressed CENP-ACse4 in the presence and absence of Psh1 by chromatin immunoprecipitation followed by high throughput sequencing. We found that ectopic CENP-ACse4 is enriched at promoters that contain histone H2A.ZHtz1 nucleosomes, but that H2A.ZHtz1 is not required for CENP-ACse4 mislocalization. Instead, the INO80 complex, which removes H2A.ZHtz1 from nucleosomes, promotes the ectopic deposition of CENP-ACse4. Transcriptional profiling revealed gene expression changes in the psh1Δ cells overexpressing CENP-ACse4. The down-regulated genes are enriched for CENP-ACse4 mislocalization to promoters, while the up-regulated genes correlate with those that are also transcriptionally up-regulated in an htz1Δ strain. Together, these data show that regulating centromeric nucleosome localization is not only critical for maintaining centromere function, but also for ensuring accurate promoter function and transcriptional regulation. Chromosomes carry the genetic material in cells. When cells divide, each daughter cell must inherit a single copy of each chromosome. The centromere is the locus on each chromosome that ensures the equal distribution of chromosomes during cell division. One essential protein involved in this task is CENP-ACse4, which normally localizes exclusively to centromeres. Here, we investigated where CENP-ACse4 spreads in the genome when parts of its regulatory machinery are removed. We found that CENP-ACse4 becomes mislocalized to promoters, the region upstream of each gene that controls the activity of the gene. Consistent with this, the mislocalization of CENP-ACse4 to promoters leads to problems with gene activity. Our work shows that mislocalization of centromeric proteins can have effects beyond chromosome segregation defects, such as interfering with gene expression on chromosome arms.
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Affiliation(s)
- Erica M. Hildebrand
- Howard Hughes Medical Institute, Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
- Molecular and Cellular Biology Program, University of Washington, Seattle, Washington, United States of America
| | - Sue Biggins
- Howard Hughes Medical Institute, Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
- * E-mail:
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A role for tuned levels of nucleosome remodeler subunit ACF1 during Drosophila oogenesis. Dev Biol 2016; 411:217-230. [PMID: 26851213 DOI: 10.1016/j.ydbio.2016.01.039] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 12/11/2015] [Accepted: 01/31/2016] [Indexed: 11/23/2022]
Abstract
The Chromatin Accessibility Complex (CHRAC) consists of the ATPase ISWI, the large ACF1 subunit and a pair of small histone-like proteins, CHRAC-14/16. CHRAC is a prototypical nucleosome sliding factor that mobilizes nucleosomes to improve the regularity and integrity of the chromatin fiber. This may facilitate the formation of repressive chromatin. Expression of the signature subunit ACF1 is restricted during embryonic development, but remains high in primordial germ cells. Therefore, we explored roles for ACF1 during Drosophila oogenesis. ACF1 is expressed in somatic and germline cells, with notable enrichment in germline stem cells and oocytes. The asymmetrical localization of ACF1 to these cells depends on the transport of the Acf1 mRNA by the Bicaudal-D/Egalitarian complex. Loss of ACF1 function in the novel Acf1(7) allele leads to defective egg chambers and their elimination through apoptosis. In addition, we find a variety of unusual 16-cell cyst packaging phenotypes in the previously known Acf1(1) allele, with a striking prevalence of egg chambers with two functional oocytes at opposite poles. Surprisingly, we found that the Acf1(1) deletion--despite disruption of the Acf1 reading frame--expresses low levels of a PHD-bromodomain module from the C-terminus of ACF1 that becomes enriched in oocytes. Expression of this module from the Acf1 genomic locus leads to packaging defects in the absence of functional ACF1, suggesting competitive interactions with unknown target molecules. Remarkably, a two-fold overexpression of CHRAC (ACF1 and CHRAC-16) leads to increased apoptosis and packaging defects. Evidently, finely tuned CHRAC levels are required for proper oogenesis.
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20
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Deniz Ö, Flores O, Aldea M, Soler-López M, Orozco M. Nucleosome architecture throughout the cell cycle. Sci Rep 2016; 6:19729. [PMID: 26818620 PMCID: PMC4730144 DOI: 10.1038/srep19729] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 09/29/2015] [Indexed: 11/09/2022] Open
Abstract
Nucleosomes provide additional regulatory mechanisms to transcription and DNA replication by mediating the access of proteins to DNA. During the cell cycle chromatin undergoes several conformational changes, however the functional significance of these changes to cellular processes are largely unexplored. Here, we present the first comprehensive genome-wide study of nucleosome plasticity at single base-pair resolution along the cell cycle in Saccharomyces cerevisiae. We determined nucleosome organization with a specific focus on two regulatory regions: transcription start sites (TSSs) and replication origins (ORIs). During the cell cycle, nucleosomes around TSSs display rearrangements in a cyclic manner. In contrast to gap (G1 and G2) phases, nucleosomes have a fuzzier organization during S and M phases, Moreover, the choreography of nucleosome rearrangements correlate with changes in gene expression during the cell cycle, indicating a strong association between nucleosomes and cell cycle-dependent gene functionality. On the other hand, nucleosomes are more dynamic around ORIs along the cell cycle, albeit with tighter regulation in early firing origins, implying the functional role of nucleosomes on replication origins. Our study provides a dynamic picture of nucleosome organization throughout the cell cycle and highlights the subsequent impact on transcription and replication activity.
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Affiliation(s)
- Özgen Deniz
- Institute for Research in Biomedicine (IRB Barcelona). Baldiri Reixac 10-12. 08028 Barcelona, Spain.,Joint BSC-CRG-IRB Program in Computational Biology. Baldiri Reixac 10-12. 08028 Barcelona, Spain
| | - Oscar Flores
- Institute for Research in Biomedicine (IRB Barcelona). Baldiri Reixac 10-12. 08028 Barcelona, Spain.,Joint BSC-CRG-IRB Program in Computational Biology. Baldiri Reixac 10-12. 08028 Barcelona, Spain
| | - Martí Aldea
- Molecular Biology Institute of Barcelona (IBMB) CSIC. Baldiri Reixac 4. 08028 Barcelona, Spain
| | - Montserrat Soler-López
- Institute for Research in Biomedicine (IRB Barcelona). Baldiri Reixac 10-12. 08028 Barcelona, Spain.,Joint BSC-CRG-IRB Program in Computational Biology. Baldiri Reixac 10-12. 08028 Barcelona, Spain
| | - Modesto Orozco
- Institute for Research in Biomedicine (IRB Barcelona). Baldiri Reixac 10-12. 08028 Barcelona, Spain.,Joint BSC-CRG-IRB Program in Computational Biology. Baldiri Reixac 10-12. 08028 Barcelona, Spain.,Department of Biochemistry and Molecular Biology. University of Barcelona, 08028 Barcelona, Spain
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21
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Systematic approaches to identify functional lncRNAs. Curr Opin Genet Dev 2016; 37:46-50. [PMID: 26821363 DOI: 10.1016/j.gde.2015.12.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Revised: 12/21/2015] [Accepted: 12/24/2015] [Indexed: 11/20/2022]
Abstract
Long noncoding RNAs (lncRNAs) were discovered in eukaryotes more than 30 years ago [1]. Recent advances in genomics have led to the discovery that lncRNAs are transcribed pervasively across the genome [2(•),3,4,5(•)]. There are an increasing number of reports that identify lncRNAs whose expression is modulated during cell differentiation or in disease states. However, biological functions for the vast majority of them are yet to be determined. Here, we propose two ways to identify lncRNAs that have biological functions: to identify lncRNAs with dedicated preinitiation complexes (PICs), and to focus on those whose transcription is highly regulated.
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McKnight RA, Yost CC, Yu X, Wiedmeier JE, Callaway CW, Brown AS, Lane RH, Fung CM. Intrauterine growth restriction perturbs nucleosome depletion at a growth hormone-responsive element in the mouse IGF-1 gene. Physiol Genomics 2015; 47:634-43. [DOI: 10.1152/physiolgenomics.00082.2015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Accepted: 10/13/2015] [Indexed: 01/08/2023] Open
Abstract
Intrauterine growth restriction (IUGR) is a common human pregnancy complication. IUGR offspring carry significant postnatal risk for early-onset metabolic syndrome, which is associated with persistent reduction in IGF-1 protein expression. We have previously shown that preadolescent IUGR male mice have decreased hepatic IGF-1 mRNA and circulating IGF-1 protein at postnatal day 21, the age when growth hormone (GH) normally upregulates hepatic IGF-1 expression. Here we studied nucleosome occupancy and CpG methylation at a putative growth hormone-responsive element in intron 2 (in2GHRE) of the hepatic IGF-1 gene in normal, sham-operated, and IUGR mice. Nucleosome occupancy and CpG methylation were determined in embryonic stem cells (ESCs) and in liver at postnatal days 14, 21, and 42. For CpG methylation, additional time points out to 2 yr were analyzed. We confirmed the putative mouse in2GHRE was GH-responsive, and in normal mice, a single nucleosome was displaced from the hepatic in2GHRE by postnatal day 21, which exposed two STAT5b DNA binding sites. Nucleosome displacement correlated with developmentally programmed CpG demethylation. Finally, IUGR significantly altered the nucleosome-depleted region (NDR) at the in2GHRE of IGF-1 on postnatal day 21, with either complete absence of the NDR or with a shifted NDR exposing only one of two STAT5b DNA binding sites. An NDR shift was also seen in offspring of sham-operated mothers. We conclude that prenatal insult such as IUGR or anesthesia/surgery could perturb the proper formation of a well-positioned NDR at the mouse hepatic IGF-1 in2GHRE necessary for transitioning to an open chromatin state.
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Affiliation(s)
- Robert A. McKnight
- Division of Neonatology, Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, Utah; and
| | - Christian C. Yost
- Division of Neonatology, Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, Utah; and
| | - Xing Yu
- Division of Neonatology, Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, Utah; and
| | - Julia E. Wiedmeier
- Division of Neonatology, Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, Utah; and
| | - Christopher W. Callaway
- Division of Neonatology, Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, Utah; and
| | - Ashley S. Brown
- Division of Neonatology, Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, Utah; and
| | - Robert H. Lane
- Division of Neonatology, Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Camille M. Fung
- Division of Neonatology, Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, Utah; and
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ACF chromatin-remodeling complex mediates stress-induced depressive-like behavior. Nat Med 2015; 21:1146-53. [PMID: 26390241 PMCID: PMC4598281 DOI: 10.1038/nm.3939] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 08/11/2015] [Indexed: 02/08/2023]
Abstract
Improved treatment for major depressive disorder (MDD) remains elusive because of the limited understanding of its underlying biological mechanisms. It is likely that stress-induced maladaptive transcriptional regulation in limbic neural circuits contributes to the development of MDD, possibly through epigenetic factors that regulate chromatin structure. We establish that persistent upregulation of the ACF (ATP-utilizing chromatin assembly and remodeling factor) ATP-dependent chromatin-remodeling complex, occurring in the nucleus accumbens of stress-susceptible mice and depressed humans, is necessary for stress-induced depressive-like behaviors. We found that altered ACF binding after chronic stress was correlated with altered nucleosome positioning, particularly around the transcription start sites of affected genes. These alterations in ACF binding and nucleosome positioning were associated with repressed expression of genes implicated in susceptibility to stress. Together, our findings identify the ACF chromatin-remodeling complex as a critical component in the development of susceptibility to depression and in regulating stress-related behaviors.
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24
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Mechanisms of Evolutionary Innovation Point to Genetic Control Logic as the Key Difference Between Prokaryotes and Eukaryotes. J Mol Evol 2015. [PMID: 26208881 DOI: 10.1007/s00239-015-9688-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The evolution of life from the simplest, original form to complex, intelligent animal life occurred through a number of key innovations. Here we present a new tool to analyze these key innovations by proposing that the process of evolutionary innovation may follow one of three underlying processes, namely a Random Walk, a Critical Path, or a Many Paths process, and in some instances may also constitute a "Pull-up the Ladder" event. Our analysis is based on the occurrence of function in modern biology, rather than specific structure or mechanism. A function in modern biology may be classified in this way either on the basis of its evolution or the basis of its modern mechanism. Characterizing key innovations in this way helps identify the likelihood that an innovation could arise. In this paper, we describe the classification, and methods to classify functional features of modern organisms into these three classes based on the analysis of how a function is implemented in modern biology. We present the application of our categorization to the evolution of eukaryotic gene control. We use this approach to support the argument that there are few, and possibly no basic chemical differences between the functional constituents of the machinery of gene control between eukaryotes, bacteria and archaea. This suggests that the difference between eukaryotes and prokaryotes that allows the former to develop the complex genetic architecture seen in animals and plants is something other than their chemistry. We tentatively identify the difference as a difference in control logic, that prokaryotic genes are by default 'on' and eukaryotic genes are by default 'off.' The Many Paths evolutionary process suggests that, from a 'default off' starting point, the evolution of the genetic complexity of higher eukaryotes is a high probability event.
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25
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Yan C, Zhang D, Raygoza Garay JA, Mwangi MM, Bai L. Decoupling of divergent gene regulation by sequence-specific DNA binding factors. Nucleic Acids Res 2015; 43:7292-305. [PMID: 26082499 PMCID: PMC4551913 DOI: 10.1093/nar/gkv618] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Accepted: 06/03/2015] [Indexed: 01/30/2023] Open
Abstract
Divergent gene pairs (DGPs) are abundant in eukaryotic genomes. Since two genes in a DGP potentially share the same regulatory sequence, one might expect that they should be co-regulated. However, an inspection of yeast DGPs containing cell-cycle or stress response genes revealed that most DGPs are differentially-regulated. The mechanism underlying DGP differential regulation is not understood. Here, we showed that co- versus differential regulation cannot be explained by genetic features including promoter length, binding site orientation, TATA elements, nucleosome distribution, or presence of non-coding RNAs. Using time-lapse fluorescence microscopy, we carried out an in-depth study of a differentially regulated DGP, PFK26-MOB1. We found that their differential regulation is mainly achieved through two DNA-binding factors, Tbf1 and Mcm1. Similar to 'enhancer-blocking insulators' in higher eukaryotes, these factors shield the proximal promoter from the action of more distant transcription regulators. We confirmed the blockage function of Tbf1 using synthetic promoters. We further presented evidence that the blockage mechanism is widely used among genome-wide DGPs. Besides elucidating the DGP regulatory mechanism, our work revealed a novel class of insulators in yeast.
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Affiliation(s)
- Chao Yan
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA Center for Eukaryotic Gene Regulation, The Pennsylvania State University, University Park, PA 16802, USA
| | - Daoyong Zhang
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA Center for Eukaryotic Gene Regulation, The Pennsylvania State University, University Park, PA 16802, USA
| | - Juan Antonio Raygoza Garay
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA Center for Infectious Disease Dynamics, The Pennsylvania State University, University Park, PA 16802, USA
| | - Michael M Mwangi
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA Center for Infectious Disease Dynamics, The Pennsylvania State University, University Park, PA 16802, USA
| | - Lu Bai
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA Center for Eukaryotic Gene Regulation, The Pennsylvania State University, University Park, PA 16802, USA Department of Physics, The Pennsylvania State University, University Park, PA 16802, USA
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26
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Li M, Hada A, Sen P, Olufemi L, Hall MA, Smith BY, Forth S, McKnight JN, Patel A, Bowman GD, Bartholomew B, Wang MD. Dynamic regulation of transcription factors by nucleosome remodeling. eLife 2015; 4. [PMID: 26047462 PMCID: PMC4456607 DOI: 10.7554/elife.06249] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 05/11/2015] [Indexed: 12/27/2022] Open
Abstract
The chromatin landscape and promoter architecture are dominated by the interplay of nucleosome and transcription factor (TF) binding to crucial DNA sequence elements. However, it remains unclear whether nucleosomes mobilized by chromatin remodelers can influence TFs that are already present on the DNA template. In this study, we investigated the interplay between nucleosome remodeling, by either yeast ISW1a or SWI/SNF, and a bound TF. We found that a TF serves as a major barrier to ISW1a remodeling, and acts as a boundary for nucleosome repositioning. In contrast, SWI/SNF was able to slide a nucleosome past a TF, with concurrent eviction of the TF from the DNA, and the TF did not significantly impact the nucleosome positioning. Our results provide direct evidence for a novel mechanism for both nucleosome positioning regulation by bound TFs and TF regulation via dynamic repositioning of nucleosomes. DOI:http://dx.doi.org/10.7554/eLife.06249.001 Cells contain thousands of genes that are encoded by molecules of DNA. In yeast and other eukaryotic organisms, this DNA is wrapped around proteins called histones to make structures called nucleosomes. This compacts the DNA and allows it to fit inside the tiny nucleus within the cell. The positioning of the nucleosomes influences how tightly packed the DNA is, which in turn influences the activity of genes. Less active genes tend to be found within regions of DNA that are tightly packed, while more active genes are found in less tightly packed regions. To activate a gene, proteins called transcription factors bind to a section of DNA within the gene called the promoter. Enzymes known as ‘chromatin remodelers’ can alter the locations of nucleosomes on DNA to allow the transcription factors access to the promoters of particular genes. In yeast, the SWI/SNF family of chromatin remodelers can disassemble nucleosomes to promote gene activity, while the ISW1 family organises nucleosomes into closely spaced groups to repress gene activity. However, it is not clear if, or how, chromatin remodelers can influence transcription factors that are already bound to DNA. Here, Li et al. studied the interactions between a transcription factor and the chromatin remodelers in yeast. The experiment used a piece of DNA that contained a bound transcription factor and a single nucleosome. Li et al. used a technique called ‘single molecule DNA unzipping’, which enabled them to precisely locate the position of the nucleosome and transcription factor before and after the nucleosome was remodeled. The experiments found that a chromatin remodeler called ISW1a moved the nucleosome away from the transcription factor, while a SWI/SNF chromatin remodeler moved the nucleosome towards it. Significantly, Li et al. also found that a transcription factor is a major barrier to ISW1a's remodeling activity, suggesting that ISW1a may use transcription factors as reference points to position nucleosomes. In contrast, SWI/SNF was able to slide a nucleosome past the transcription factor, which led to the transcription factor falling off the DNA. Therefore, SWI/SNF is able to move transcription factors out of the way to deactivate genes. Li et al. propose a new model for how chromatin remodelers can move nucleosomes and regulate transcription factors to alter gene activity. A future challenge will be to observe these types of activities in living cells. DOI:http://dx.doi.org/10.7554/eLife.06249.002
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Affiliation(s)
- Ming Li
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, United States
| | - Arjan Hada
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, United States
| | - Payel Sen
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, United States
| | - Lola Olufemi
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, United States
| | - Michael A Hall
- Department of Physics, Laboratory of Atomic and Solid State Physics, Howard Hughes Medical Institute, Cornell University, Ithaca, United States
| | - Benjamin Y Smith
- Department of Physics, Laboratory of Atomic and Solid State Physics, Howard Hughes Medical Institute, Cornell University, Ithaca, United States
| | - Scott Forth
- Department of Physics, Laboratory of Atomic and Solid State Physics, Howard Hughes Medical Institute, Cornell University, Ithaca, United States
| | - Jeffrey N McKnight
- Thomas C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, United States
| | - Ashok Patel
- Thomas C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, United States
| | - Gregory D Bowman
- Thomas C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, United States
| | - Blaine Bartholomew
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, United States
| | - Michelle D Wang
- Department of Physics, Laboratory of Atomic and Solid State Physics, Howard Hughes Medical Institute, Cornell University, Ithaca, United States
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Global alterations of the transcriptional landscape during yeast growth and development in the absence of Ume6-dependent chromatin modification. Mol Genet Genomics 2015; 290:2031-46. [PMID: 25957495 DOI: 10.1007/s00438-015-1051-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Accepted: 04/17/2015] [Indexed: 10/23/2022]
Abstract
Chromatin modification enzymes are important regulators of gene expression and some are evolutionarily conserved from yeast to human. Saccharomyces cerevisiae is a major model organism for genome-wide studies that aim at the identification of target genes under the control of conserved epigenetic regulators. Ume6 interacts with the upstream repressor site 1 (URS1) and represses transcription by recruiting both the conserved histone deacetylase Rpd3 (through the co-repressor Sin3) and the chromatin-remodeling factor Isw2. Cells lacking Ume6 are defective in growth, stress response, and meiotic development. RNA profiling studies and in vivo protein-DNA binding assays identified mRNAs or transcript isoforms that are directly repressed by Ume6 in mitosis. However, a comprehensive understanding of the transcriptional alterations, which underlie the complex ume6Δ mutant phenotype during fermentation, respiration, or sporulation, is lacking. We report the protein-coding transcriptome of a diploid MAT a/α wild-type and ume6/ume6 mutant strains cultured in rich media with glucose or acetate as a carbon source, or sporulation-inducing medium. We distinguished direct from indirect effects on mRNA levels by combining GeneChip data with URS1 motif predictions and published high-throughput in vivo Ume6-DNA binding data. To gain insight into the molecular interactions between successive waves of Ume6-dependent meiotic genes, we integrated expression data with information on protein networks. Our work identifies novel Ume6 repressed genes during growth and development and reveals a strong effect of the carbon source on the derepression pattern of transcripts in growing and developmentally arrested ume6/ume6 mutant cells. Since yeast is a useful model organism for chromatin-mediated effects on gene expression, our results provide a rich source for further genetic and molecular biological work on the regulation of cell growth and cell differentiation in eukaryotes.
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Chromatin remodeling factors Isw2 and Ino80 regulate checkpoint activity and chromatin structure in S phase. Genetics 2015; 199:1077-91. [PMID: 25701287 DOI: 10.1534/genetics.115.174730] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 02/13/2015] [Indexed: 12/19/2022] Open
Abstract
When cells undergo replication stress, proper checkpoint activation and deactivation are critical for genomic stability and cell survival and therefore must be highly regulated. Although mechanisms of checkpoint activation are well studied, mechanisms of checkpoint deactivation are far less understood. Previously, we reported that chromatin remodeling factors Isw2 and Ino80 attenuate the S-phase checkpoint activity in Saccharomyces cerevisiae, especially during recovery from hydroxyurea. In this study, we found that Isw2 and Ino80 have a more pronounced role in attenuating checkpoint activity during late S phase in the presence of methyl methanesulfonate (MMS). We therefore screened for checkpoint factors required for Isw2 and Ino80 checkpoint attenuation in the presence of MMS. Here we demonstrate that Isw2 and Ino80 antagonize checkpoint activators and attenuate checkpoint activity in S phase in MMS either through a currently unknown pathway or through RPA. Unexpectedly, we found that Isw2 and Ino80 increase chromatin accessibility around replicating regions in the presence of MMS through a novel mechanism. Furthermore, through growth assays, we provide additional evidence that Isw2 and Ino80 partially counteract checkpoint activators specifically in the presence of MMS. Based on these results, we propose that Isw2 and Ino80 attenuate S-phase checkpoint activity through a novel mechanism.
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Porrua O, Libri D. Transcription termination and the control of the transcriptome: why, where and how to stop. Nat Rev Mol Cell Biol 2015; 16:190-202. [DOI: 10.1038/nrm3943] [Citation(s) in RCA: 201] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Abstract
Long noncoding RNAs (lncRNAs) are pervasively transcribed across eukaryotic genomes, but functions of only a very small subset of them have been demonstrated. This has led to active debate about whether many of them have any biological functions. In addition, very few regulators of lncRNAs have been identified. We developed a novel genetic screen using reconstituted RNAi in Saccharomyces cerevisiae and systematically identified a large number of putative lncRNA repressors. Among them, we found that four highly conserved chromatin remodeling factors are global lncRNA repressors that play major roles in shaping the eukaryotic lncRNA transcriptome. Importantly, we identified >250 antisense lncRNAs (CRRATs [chromatin remodeling-repressed antisense transcripts]) whose repression by these chromatin remodeling factors is required for the maintenance of normal levels of overlapping mRNA transcripts. Our results strongly suggest that regulation of mRNA through repression of antisense lncRNAs is far more broadly used than previously appreciated.
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Bogenschutz NL, Rodriguez J, Tsukiyama T. Initiation of DNA replication from non-canonical sites on an origin-depleted chromosome. PLoS One 2014; 9:e114545. [PMID: 25486280 PMCID: PMC4259332 DOI: 10.1371/journal.pone.0114545] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2014] [Accepted: 11/11/2014] [Indexed: 12/18/2022] Open
Abstract
Eukaryotic DNA replication initiates from multiple sites on each chromosome called replication origins (origins). In the budding yeast Saccharomyces cerevisiae, origins are defined at discrete sites. Regular spacing and diverse firing characteristics of origins are thought to be required for efficient completion of replication, especially in the presence of replication stress. However, a S. cerevisiae chromosome III harboring multiple origin deletions has been reported to replicate relatively normally, and yet how an origin-deficient chromosome could accomplish successful replication remains unknown. To address this issue, we deleted seven well-characterized origins from chromosome VI, and found that these deletions do not cause gross growth defects even in the presence of replication inhibitors. We demonstrated that the origin deletions do cause a strong decrease in the binding of the origin recognition complex. Unexpectedly, replication profiling of this chromosome showed that DNA replication initiates from non-canonical loci around deleted origins in yeast. These results suggest that replication initiation can be unexpectedly flexible in this organism.
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Affiliation(s)
- Naomi L. Bogenschutz
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
- Molecular and Cellular Biology Program, University of Washington and Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Jairo Rodriguez
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Toshio Tsukiyama
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
- * E-mail:
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Koster MJE, Timmers HTM. Regulation of anti-sense transcription by Mot1p and NC2 via removal of TATA-binding protein (TBP) from the 3'-end of genes. Nucleic Acids Res 2014; 43:143-52. [PMID: 25432956 PMCID: PMC4288163 DOI: 10.1093/nar/gku1263] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The activity and dynamic nature of TATA-binding protein (TBP) crucial to RNA polymerase II-mediated transcription is under control of the Mot1p and NC2 complexes. Here we show that both TBP regulatory factors play ‘hidden’ roles in ensuring transcription fidelity by restricting anti-sense non-coding RNA (ncRNA) synthesis. Production of anti-sense ncRNA transcripts is suppressed by Mot1p- and NC2-mediated release of TBP from binding sites at the 3′-end of genes. In this, Mot1p and NC2 collaborate with the Nrd1p–Nab3p–Sen1p (NNS) complex that terminates the synthesis of anti-sense ncRNAs. In several cases anti-sense ncRNA expression interferes with expression of the cognate sense transcript. Our data reveal a novel regulatory mechanism to suppress anti-sense ncRNA expression and pre-initiation complex (PIC) formation at spurious sites.
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Affiliation(s)
- Maria J E Koster
- Department of Molecular Cancer Research, Center for Molecular Medicine, University Medical Center Utrecht, 3584 CG, Utrecht, The Netherlands
| | - H Th Marc Timmers
- Department of Molecular Cancer Research, Center for Molecular Medicine, University Medical Center Utrecht, 3584 CG, Utrecht, The Netherlands
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Schmidt HG, Sewitz S, Andrews SS, Lipkow K. An integrated model of transcription factor diffusion shows the importance of intersegmental transfer and quaternary protein structure for target site finding. PLoS One 2014; 9:e108575. [PMID: 25333780 PMCID: PMC4204827 DOI: 10.1371/journal.pone.0108575] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2014] [Accepted: 08/30/2014] [Indexed: 11/30/2022] Open
Abstract
We present a computational model of transcription factor motion that explains both the observed rapid target finding of transcription factors, and how this motion influences protein and genome structure. Using the Smoldyn software, we modelled transcription factor motion arising from a combination of unrestricted 3D diffusion in the nucleoplasm, sliding along the DNA filament, and transferring directly between filament sections by intersegmental transfer. This presents a fine-grain picture of the way in which transcription factors find their targets two orders of magnitude faster than 3D diffusion alone allows. Eukaryotic genomes contain sections of nucleosome free regions (NFRs) around the promoters; our model shows that the presence and size of these NFRs can be explained as their acting as antennas on which transcription factors slide to reach their targets. Additionally, our model shows that intersegmental transfer may have shaped the quaternary structure of transcription factors: sequence specific DNA binding proteins are unusually enriched in dimers and tetramers, perhaps because these allow intersegmental transfer, which accelerates target site finding. Finally, our model shows that a ‘hopping’ motion can emerge from 3D diffusion on small scales. This explains the apparently long sliding lengths that have been observed for some DNA binding proteins observed in vitro. Together, these results suggest that transcription factor diffusion dynamics help drive the evolution of protein and genome structure.
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Affiliation(s)
- Hugo G. Schmidt
- Department of Biochemistry & Cambridge Systems Biology Centre, University of Cambridge, Cambridge, United Kingdom
- * E-mail: (HS); (KL)
| | - Sven Sewitz
- Department of Biochemistry & Cambridge Systems Biology Centre, University of Cambridge, Cambridge, United Kingdom
- Nuclear Dynamics Programme, The Babraham Institute, Cambridge, United Kingdom
| | - Steven S. Andrews
- Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Karen Lipkow
- Department of Biochemistry & Cambridge Systems Biology Centre, University of Cambridge, Cambridge, United Kingdom
- Nuclear Dynamics Programme, The Babraham Institute, Cambridge, United Kingdom
- * E-mail: (HS); (KL)
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Li G, Liu S, Wang J, He J, Huang H, Zhang Y, Xu L. ISWI proteins participate in the genome-wide nucleosome distribution in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2014; 78:706-14. [PMID: 24606212 DOI: 10.1111/tpj.12499] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Revised: 01/28/2014] [Accepted: 02/24/2014] [Indexed: 05/25/2023]
Abstract
Chromatin is a highly organized structure with repetitive nucleosome subunits. Nucleosome distribution patterns, which contain information on epigenetic controls, are dynamically affected by ATP-dependent chromatin remodeling factors (remodelers). However, whether plants have specific nucleosome distribution patterns and how plant remodelers contribute to the pattern formation are not clear. In this study we used the micrococcal nuclease digestion followed by deep sequencing (MNase-seq) assay to show the genome-wide nucleosome pattern in Arabidopsis thaliana. We demonstrated that the nucleosome distribution patterns of Arabidopsis are associated with the gene expression level, and have several specific characteristics that are different from those of animals and yeast. In addition, we found that remodelers in the A. thaliana imitation switch (AtISWI) subfamily are important for the formation of the nucleosome distribution pattern. Double mutations in the AtISWI genes, CHROMATIN REMODELING 11 (CHR11) and CHR17, resulted in the loss of the evenly spaced nucleosome pattern in gene bodies, but did not affect nucleosome density, supporting a previous idea that the primary role of ISWI is to slide nucleosomes in gene bodies for pattern formation.
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Affiliation(s)
- Guang Li
- National Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai, 200032, China
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Lake RJ, Boetefuer EL, Tsai PF, Jeong J, Choi I, Won KJ, Fan HY. The sequence-specific transcription factor c-Jun targets Cockayne syndrome protein B to regulate transcription and chromatin structure. PLoS Genet 2014; 10:e1004284. [PMID: 24743307 PMCID: PMC3990521 DOI: 10.1371/journal.pgen.1004284] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Accepted: 02/20/2014] [Indexed: 11/19/2022] Open
Abstract
Cockayne syndrome is an inherited premature aging disease associated with numerous developmental and neurological defects, and mutations in the gene encoding the CSB protein account for the majority of Cockayne syndrome cases. Accumulating evidence suggests that CSB functions in transcription regulation, in addition to its roles in DNA repair, and those defects in this transcriptional activity might contribute to the clinical features of Cockayne syndrome. Transcription profiling studies have so far uncovered CSB-dependent effects on gene expression; however, the direct targets of CSB's transcriptional activity remain largely unknown. In this paper, we report the first comprehensive analysis of CSB genomic occupancy during replicative cell growth. We found that CSB occupancy sites display a high correlation to regions with epigenetic features of promoters and enhancers. Furthermore, we found that CSB occupancy is enriched at sites containing the TPA-response element. Consistent with this binding site preference, we show that CSB and the transcription factor c-Jun can be found in the same protein-DNA complex, suggesting that c-Jun can target CSB to specific genomic regions. In support of this notion, we observed decreased CSB occupancy of TPA-response elements when c-Jun levels were diminished. By modulating CSB abundance, we found that CSB can influence the expression of nearby genes and impact nucleosome positioning in the vicinity of its binding site. These results indicate that CSB can be targeted to specific genomic loci by sequence-specific transcription factors to regulate transcription and local chromatin structure. Additionally, comparison of CSB occupancy sites with the MSigDB Pathways database suggests that CSB might function in peroxisome proliferation, EGF receptor transactivation, G protein signaling and NF-κB activation, shedding new light on the possible causes and mechanisms of Cockayne syndrome. Cockayne syndrome is a devastating inherited disease, in which patients appear to age prematurely, have sun sensitivity and suffer from profound neurological and developmental defects. Mutations in the CSB gene account for the majority of Cockayne syndrome cases. CSB is an ATP-dependent chromatin remodeler, and these proteins can use energy from ATP-hydrolysis to alter contacts between DNA and histones of a nucleosome, the basic units of chromatin structure. CSB functions in DNA repair, but accumulating evidence reveals that CSB also functions in transcription regulation. Here, we determined the genomic localization of CSB to identify its gene targets and found that CSB occupancy displays high correlation to regions with epigenetic features of promoters and enhancers. Furthermore, CSB is enriched at genomic regions containing the binding site for the c-Jun transcription factor, and we found that these two proteins interact, uncovering a new targeting mechanism for CSB. We also demonstrate that CSB can influence gene expression in the vicinity of its binding sites and alter local chromatin structure. Together, this study supports the hypothesis that defects in the regulation of gene expression and chromatin structure by CSB might contribute to the diverse clinical features of Cockayne syndrome.
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Affiliation(s)
- Robert J. Lake
- Epigenetics Program, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Erica L. Boetefuer
- Epigenetics Program, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Biology Graduate Program, Graduate School of Arts and Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Pei-Fang Tsai
- Epigenetics Program, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Jieun Jeong
- Epigenetics Program, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Institute for Diabetes Obesity and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Inchan Choi
- Institute for Diabetes Obesity and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Kyoung-Jae Won
- Epigenetics Program, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Institute for Diabetes Obesity and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Hua-Ying Fan
- Epigenetics Program, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Institute for Diabetes Obesity and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- * E-mail:
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Mueller-Planitz F, Klinker H, Becker PB. Nucleosome sliding mechanisms: new twists in a looped history. Nat Struct Mol Biol 2013; 20:1026-32. [PMID: 24008565 DOI: 10.1038/nsmb.2648] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Accepted: 07/12/2013] [Indexed: 01/11/2023]
Abstract
Nucleosomes, the basic organizational units of chromatin, package and regulate eukaryotic genomes. ATP-dependent nucleosome-remodeling factors endow chromatin with structural flexibility by promoting assembly or disruption of nucleosomes and the exchange of histone variants. Furthermore, most remodeling factors induce nucleosome movements through sliding of histone octamers on DNA. We summarize recent progress toward unraveling the basic nucleosome sliding mechanism and the interplay of the remodelers' DNA translocases with accessory domains. Such domains optimize and regulate the basic sliding reaction and exploit sliding to achieve diverse structural effects, such as nucleosome positioning or eviction, or the regular spacing of nucleosomes in chromatin.
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Affiliation(s)
- Felix Mueller-Planitz
- 1] Adolf-Butenandt-Institute, Ludwig-Maximilians-Universität, Munich, Germany. [2] Center for Integrated Protein Science Munich, Ludwig-Maximilians-Universität, Munich, Germany
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Nekrasov M, Soboleva TA, Jack C, Tremethick DJ. Histone variant selectivity at the transcription start site: H2A.Z or H2A.Lap1. Nucleus 2013; 4:431-8. [PMID: 24213378 PMCID: PMC3925687 DOI: 10.4161/nucl.26862] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Considerable attention has been given to the understanding of how nucleosomes are altered or removed from the transcription start site of RNA polymerase II genes to enable transcription to proceed. This has led to the view that for transcriptional activation to occur, the transcription start site (TSS) must become depleted of nucleosomes. However, we have shown that this is not the case with different unstable histone H2A variant-containing nucleosomes occupying the TSS under different physiological settings. For example, during mouse spermatogenesis we found that the mouse homolog of human H2A.Bbd, H2A.Lap1, is targeted to the TSS of active genes expressed during specific stages of spermatogenesis. On the other hand, we observed in trophoblast stem cells, a H2A.Z-containing nucleosome occupying the TSS of genes active in the G1 phase of the cell cycle. Notably, this H2A.Z-containing nucleosome was different compared with other promoter specific H2A.Z nucleosomes by being heterotypic rather than being homotypic. In other words, it did not contain the expected two copies of H2A.Z per nucleosome but only one (i.e., H2A.Z/H2A rather than H2A.Z/H2A.Z). Given these observations, we wondered whether the histone variant composition of a nucleosome at an active TSS could in fact vary in the same cell type. To investigate this possibility, we performed H2A.Z ChIP-H2A reChIP assays in the mouse testis and compared this data with our testis H2A.Lap1 ChIP-seq data. Indeed, we find that different promoters involved in the expression of genes involved in distinct biological processes can contain either H2A.Z/H2A or H2A.Lap1. This argues that specific mechanisms exist, which can determine whether H2A.Z or H2A.Lap1 is targeted to the TSS of an active gene.
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Affiliation(s)
- Maxim Nekrasov
- The John Curtin School of Medical Research; The Australian National University; Canberra, Australia
| | - Tatiana A Soboleva
- The John Curtin School of Medical Research; The Australian National University; Canberra, Australia
| | - Cameron Jack
- The John Curtin School of Medical Research; The Australian National University; Canberra, Australia
| | - David J Tremethick
- The John Curtin School of Medical Research; The Australian National University; Canberra, Australia
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39
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Perales R, Erickson B, Zhang L, Kim H, Valiquett E, Bentley D. Gene promoters dictate histone occupancy within genes. EMBO J 2013; 32:2645-56. [PMID: 24013117 DOI: 10.1038/emboj.2013.194] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2013] [Accepted: 07/30/2013] [Indexed: 11/09/2022] Open
Abstract
Spt6 is a transcriptional elongation factor and histone chaperone that reassembles transcribed chromatin. Genome-wide H3 mapping showed that Spt6 preferentially maintains nucleosomes within the first 500 bases of genes and helps define nucleosome-depleted regions in 5' and 3' flanking sequences. In Spt6-depleted cells, H3 loss at 5' ends correlates with reduced pol II density suggesting enhanced transcription elongation. Consistent with its 'Suppressor of Ty' (Spt) phenotype, Spt6 inactivation caused localized H3 eviction over 1-2 nucleosomes at 5' ends of Ty elements. H3 displacement differed between genes driven by promoters with 'open'/DPN and 'closed'/OPN chromatin conformations with similar pol II densities. More eviction occurred on genes with 'closed' promoters, associated with 'noisy' transcription. Moreover, swapping of 'open' and 'closed' promoters showed that they can specify distinct downstream patterns of histone eviction/deposition. These observations suggest a novel function for promoters in dictating histone dynamics within genes possibly through effects on transcriptional bursting or elongation rate.
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Affiliation(s)
- Roberto Perales
- Program in Molecular Biology, Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, CO, USA
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Abstract
Eukaryotic chromatin is kept flexible and dynamic to respond to environmental, metabolic, and developmental cues through the action of a family of so-called "nucleosome remodeling" ATPases. Consistent with their helicase ancestry, these enzymes experience conformation changes as they bind and hydrolyze ATP. At the same time they interact with DNA and histones, which alters histone-DNA interactions in target nucleosomes. Their action may lead to complete or partial disassembly of nucleosomes, the exchange of histones for variants, the assembly of nucleosomes, or the movement of histone octamers on DNA. "Remodeling" may render DNA sequences accessible to interacting proteins or, conversely, promote packing into tightly folded structures. Remodeling processes participate in every aspect of genome function. Remodeling activities are commonly integrated with other mechanisms such as histone modifications or RNA metabolism to assemble stable, epigenetic states.
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Arnold C, Stadler PF, Prohaska SJ. Chromatin computation: epigenetic inheritance as a pattern reconstruction problem. J Theor Biol 2013; 336:61-74. [PMID: 23880640 DOI: 10.1016/j.jtbi.2013.07.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Revised: 07/02/2013] [Accepted: 07/15/2013] [Indexed: 01/19/2023]
Abstract
Eukaryotic histones carry a diverse set of specific chemical modifications that accumulate over the life-time of a cell and have a crucial impact on the cell state in general and the transcriptional program in particular. Replication constitutes a dramatic disruption of the chromatin states that effectively amounts to partial erasure of stored information. To preserve its epigenetic state the cell reconstructs (at least part of) the histone modifications by means of processes that are still very poorly understood. A plausible hypothesis is that the different combinations of reader and writer domains in histone-modifying enzymes implement local rewriting rules that are capable of "recomputing" the desired parental modification patterns on the basis of the partial information contained in that half of the nucleosomes that predate replication. To test whether such a mechanism is theoretically feasible, we have developed a flexible stochastic simulation system (available at http://www.bioinf.uni-leipzig.de/Software/StoChDyn) for studying the dynamics of histone modification states. The implementation is based on Gillespie's approach, i.e., it models the master equation of a detailed chemical model. It is efficient enough to use an evolutionary algorithm to find patterns across multiple cell divisions with high accuracy. We found that it is easy to evolve a system of enzymes that can maintain a particular chromatin state roughly stable, even without explicit boundary elements separating differentially modified chromatin domains. However, the success of this task depends on several previously unanticipated factors, such as the length of the initial state, the specific pattern that should be maintained, the time between replications, and chemical parameters such as enzymatic binding and dissociation rates. All these factors also influence the accumulation of errors in the wake of cell divisions.
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Affiliation(s)
- Christian Arnold
- Computational EvoDevo Group, Department of Computer Science, Universität Leipzig, Härtelstraße 16-18, 04107 Leipzig, Germany; Interdisciplinary Center for Bioinformatics, Universität Leipzig, Härtelstraße 16-18, 04107 Leipzig, Germany; Harvard University, Department of Human Evolutionary Biology, 11 Divinity Avenue, Cambridge, MA 02138, USA.
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Byeon B, Wang W, Barski A, Ranallo RT, Bao K, Schones DE, Zhao K, Wu C, Wu WH. The ATP-dependent chromatin remodeling enzyme Fun30 represses transcription by sliding promoter-proximal nucleosomes. J Biol Chem 2013; 288:23182-93. [PMID: 23779104 DOI: 10.1074/jbc.m113.471979] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The evolutionarily conserved ATP-dependent chromatin remodeling enzyme Fun30 has recently been shown to play important roles in heterochromatin silencing and DNA repair. However, how Fun30 remodels nucleosomes is not clear. Here we report a nucleosome sliding activity of Fun30 and its role in transcriptional repression. We observed that Fun30 repressed the expression of genes involved in amino acid and carbohydrate metabolism, the stress response, and meiosis. In addition, Fun30 was localized at the 5' and 3' ends of genes and within the open reading frames of its targets. Consistent with its role in gene repression, we observed that Fun30 target genes lacked histone modifications often associated with gene activation and showed an increased level of ubiquitinated histone H2B. Furthermore, a genome-wide nucleosome mapping analysis revealed that the length of the nucleosome-free region at the 5' end of a subset of genes was changed in Fun30-depleted cells. In addition, the positions of the -1, +2, and +3 nucleosomes at the 5' end of target genes were shifted significantly, whereas the position of the +1 nucleosome remained largely unchanged in the fun30Δ mutant. Finally, we demonstrated that affinity-purified, single-component Fun30 exhibited a nucleosome sliding activity in an ATP-dependent manner. These results define a role for Fun30 in the regulation of transcription and indicate that Fun30 remodels chromatin at the 5' end of genes by sliding promoter-proximal nucleosomes.
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Affiliation(s)
- Boseon Byeon
- Institute of Molecular Medicine and Genetics, Department of Neurology, Medical College of Georgia, Georgia Regents University, Augusta, Georgia 30912, USA
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Venkatesh S, Workman JL, Smolle M. UpSETing chromatin during non-coding RNA production. Epigenetics Chromatin 2013; 6:16. [PMID: 23738864 PMCID: PMC3680234 DOI: 10.1186/1756-8935-6-16] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Accepted: 05/10/2013] [Indexed: 01/01/2023] Open
Abstract
The packaging of eukaryotic DNA into nucleosomal arrays permits cells to tightly regulate and fine-tune gene expression. The ordered disassembly and reassembly of these nucleosomes allows RNA polymerase II (RNAPII) conditional access to the underlying DNA sequences. Disruption of nucleosome reassembly following RNAPII passage results in spurious transcription initiation events, leading to the production of non-coding RNA (ncRNA). We review the molecular mechanisms involved in the suppression of these cryptic initiation events and discuss the role played by ncRNAs in regulating gene expression.
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Affiliation(s)
- Swaminathan Venkatesh
- Stowers Institute for Medical Research, 1000 E 50th Street, Kansas City, MO 64110, USA.
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DNA looping facilitates targeting of a chromatin remodeling enzyme. Mol Cell 2013; 50:93-103. [PMID: 23478442 DOI: 10.1016/j.molcel.2013.02.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Revised: 01/15/2013] [Accepted: 01/30/2013] [Indexed: 12/14/2022]
Abstract
ATP-dependent chromatin remodeling enzymes are highly abundant and play pivotal roles regulating DNA-dependent processes. The mechanisms by which they are targeted to specific loci have not been well understood on a genome-wide scale. Here, we present evidence that a major targeting mechanism for the Isw2 chromatin remodeling enzyme to specific genomic loci is through sequence-specific transcription factor (TF)-dependent recruitment. Unexpectedly, Isw2 is recruited in a TF-dependent fashion to a large number of loci without TF binding sites. Using the 3C assay, we show that Isw2 can be targeted by Ume6- and TFIIB-dependent DNA looping. These results identify DNA looping as a mechanism for the recruitment of a chromatin remodeling enzyme and define a function for DNA looping. We also present evidence suggesting that Ume6-dependent DNA looping is involved in chromatin remodeling and transcriptional repression, revealing a mechanism by which the three-dimensional folding of chromatin affects DNA-dependent processes.
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Zentner GE, Tsukiyama T, Henikoff S. ISWI and CHD chromatin remodelers bind promoters but act in gene bodies. PLoS Genet 2013; 9:e1003317. [PMID: 23468649 PMCID: PMC3585014 DOI: 10.1371/journal.pgen.1003317] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Accepted: 12/27/2012] [Indexed: 11/19/2022] Open
Abstract
ATP-dependent nucleosome remodelers influence genetic processes by altering nucleosome occupancy, positioning, and composition. In vitro, Saccharomyces cerevisiae ISWI and CHD remodelers require ∼30-85 bp of extranucleosomal DNA to reposition nucleosomes, but linker DNA in S. cerevisiae averages <20 bp. To address this discrepancy between in vitro and in vivo observations, we have mapped the genomic distributions of the yeast Isw1, Isw2, and Chd1 remodelers at base-pair resolution on native chromatin. Although these remodelers act in gene bodies, we find that they are also highly enriched at nucleosome-depleted regions (NDRs), where they bind to extended regions of DNA adjacent to particular transcription factors. Surprisingly, catalytically inactive remodelers show similar binding patterns. We find that remodeler occupancy at NDRs and gene bodies is associated with nucleosome turnover and transcriptional elongation rate, suggesting that remodelers act on regions of transient nucleosome unwrapping or depletion within gene bodies subsequent to transcriptional elongation.
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Affiliation(s)
- Gabriel E. Zentner
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Toshio Tsukiyama
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Steven Henikoff
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
- Howard Hughes Medical Institute, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
- * E-mail:
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Rodriguez J, Tsukiyama T. ATR-like kinase Mec1 facilitates both chromatin accessibility at DNA replication forks and replication fork progression during replication stress. Genes Dev 2013; 27:74-86. [PMID: 23307868 DOI: 10.1101/gad.202978.112] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Faithful DNA replication is essential for normal cell division and differentiation. In eukaryotic cells, DNA replication takes place on chromatin. This poses the critical question as to how DNA replication can progress through chromatin, which is inhibitory to all DNA-dependent processes. Here, we developed a novel genome-wide method to measure chromatin accessibility to micrococcal nuclease (MNase) that is normalized for nucleosome density, the NCAM (normalized chromatin accessibility to MNase) assay. This method enabled us to discover that chromatin accessibility increases specifically at and ahead of DNA replication forks in normal S phase and during replication stress. We further found that Mec1, a key regulatory ATR-like kinase in the S-phase checkpoint, is required for both normal chromatin accessibility around replication forks and replication fork rate during replication stress, revealing novel functions for the kinase in replication stress response. These results suggest a possibility that Mec1 may facilitate DNA replication fork progression during replication stress by increasing chromatin accessibility around replication forks.
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Affiliation(s)
- Jairo Rodriguez
- Fred Hutchinson Cancer Research Center, Division of Basic Sciences, Seattle, Washington 98109, USA
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48
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Abstract
Unstable non-coding RNAs are produced from thousands of loci in all studied eukaryotes (and also prokaryotes), but remain of largely unknown function. The present review summarizes the mechanisms of eukaryotic non-coding RNA degradation and highlights recent findings regarding function. The focus is primarily on budding yeast where the bulk of this research has been performed, but includes results from higher eukaryotes where available.
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Chen K, Wilson MA, Hirsch C, Watson A, Liang S, Lu Y, Li W, Dent SYR. Stabilization of the promoter nucleosomes in nucleosome-free regions by the yeast Cyc8-Tup1 corepressor. Genome Res 2012; 23:312-22. [PMID: 23124522 PMCID: PMC3561872 DOI: 10.1101/gr.141952.112] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The yeast Cyc8 (also known as Ssn6)–Tup1 complex regulates gene expression through a variety of mechanisms, including positioning of nucleosomes over promoters of some target genes to limit accessibility to the transcription machinery. To further define the functions of Cyc8–Tup1 in gene regulation and chromatin remodeling, we performed genome-wide profiling of changes in nucleosome organization and gene expression that occur upon loss of CYC8 or TUP1 and observed extensive nucleosome alterations in both promoters and gene bodies of derepressed genes. Our improved nucleosome profiling and analysis approaches revealed low-occupancy promoter nucleosomes (P nucleosomes) at locations previously defined as nucleosome-free regions. In the absence of CYC8 or TUP1, this P nucleosome is frequently lost, whereas nucleosomes are gained at −1 and +1 positions, accompanying up-regulation of downstream genes. Our analysis of public ChIP-seq data revealed that Cyc8 and Tup1 preferentially bind TATA-containing promoters, which are also enriched in genes derepressed upon loss of CYC8 or TUP1. These results suggest that stabilization of the P nucleosome on TATA-containing promoters may be a central feature of the repressive chromatin architecture created by the Cyc8–Tup1 corepressor, and that releasing the P nucleosome contributes to gene activation.
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Affiliation(s)
- Kaifu Chen
- Division of Biostatistics, Dan L Duncan Cancer Center, Baylor College of Medicine, Houston, Texas 77030, USA
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Timing of transcriptional quiescence during gametogenesis is controlled by global histone H3K4 demethylation. Dev Cell 2012; 23:1059-71. [PMID: 23123093 DOI: 10.1016/j.devcel.2012.10.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Revised: 08/10/2012] [Accepted: 10/01/2012] [Indexed: 11/22/2022]
Abstract
Gametes are among the most highly specialized cells produced during development. Although gametogenesis culminates in transcriptional quiescence in plants and animals, regulatory mechanisms controlling this are unknown. Here, we confirm that gamete differentiation in the single-celled yeast Saccharomyces cerevisiae is accompanied by global transcriptional shutoff following the completion of meiosis. We show that Jhd2, a highly conserved JARID1-family histone H3K4 demethylase, activates protein-coding gene transcription in opposition to this programmed transcriptional shutoff, sustaining the period of productive transcription during spore differentiation. Moreover, using genome-wide nucleosome, H3K4me, and transcript mapping experiments, we demonstrate that JHD2 globally represses intergenic noncoding transcription during this period. The widespread transcriptional defects of JHD2 mutants are associated with precocious differentiation and the production of stress-sensitive spores, demonstrating that Jhd2 regulation of the global postmeiotic transcriptional program is critical for the production of healthy meiotic progeny.
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