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Lorenzi A, Legeai F, Jouan V, Girard PA, Strand MR, Ravallec M, Eychenne M, Bretaudeau A, Robin S, Rochefort J, Villegas M, Burke GR, Rebollo R, Nègre N, Volkoff AN. Identification of a viral gene essential for the genome replication of a domesticated endogenous virus in ichneumonid parasitoid wasps. PLoS Pathog 2024; 20:e1011980. [PMID: 38662774 DOI: 10.1371/journal.ppat.1011980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Revised: 05/07/2024] [Accepted: 03/22/2024] [Indexed: 05/08/2024] Open
Abstract
Thousands of endoparasitoid wasp species in the families Braconidae and Ichneumonidae harbor "domesticated endogenous viruses" (DEVs) in their genomes. This study focuses on ichneumonid DEVs, named ichnoviruses (IVs). Large quantities of DNA-containing IV virions are produced in ovary calyx cells during the pupal and adult stages of female wasps. Females parasitize host insects by injecting eggs and virions into the body cavity. After injection, virions rapidly infect host cells which is followed by expression of IV genes that promote the successful development of wasp offspring. IV genomes consist of two components: proviral segment loci that serve as templates for circular dsDNAs that are packaged into capsids, and genes from an ancestral virus that produce virions. In this study, we generated a chromosome-scale genome assembly for Hyposoter didymator that harbors H. didymator ichnovirus (HdIV). We identified a total of 67 HdIV loci that are amplified in calyx cells during the wasp pupal stage. We then focused on an HdIV gene, U16, which is transcribed in calyx cells during the initial stages of replication. Sequence analysis indicated that U16 contains a conserved domain in primases from select other viruses. Knockdown of U16 by RNA interference inhibited virion morphogenesis in calyx cells. Genome-wide analysis indicated U16 knockdown also inhibited amplification of HdIV loci in calyx cells. Altogether, our results identified several previously unknown HdIV loci, demonstrated that all HdIV loci are amplified in calyx cells during the pupal stage, and showed that U16 is required for amplification and virion morphogenesis.
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Affiliation(s)
- Ange Lorenzi
- DGIMI, Univ Montpellier, INRAE, Montpellier, France
- Department of Entomology, University of Georgia, Athens, Georgia, United States of America
| | - Fabrice Legeai
- INRAE, UMR Institut de Génétique, Environnement et Protection des Plantes (IGEPP), BioInformatics Platform for Agroecosystems Arthropods (BIPAA), Campus Beaulieu, Rennes, France
- INRIA, IRISA, GenOuest Core Facility, Campus de Beaulieu, Rennes, France
| | | | | | - Michael R Strand
- Department of Entomology, University of Georgia, Athens, Georgia, United States of America
| | | | | | - Anthony Bretaudeau
- INRAE, UMR Institut de Génétique, Environnement et Protection des Plantes (IGEPP), BioInformatics Platform for Agroecosystems Arthropods (BIPAA), Campus Beaulieu, Rennes, France
- INRIA, IRISA, GenOuest Core Facility, Campus de Beaulieu, Rennes, France
| | - Stéphanie Robin
- INRAE, UMR Institut de Génétique, Environnement et Protection des Plantes (IGEPP), BioInformatics Platform for Agroecosystems Arthropods (BIPAA), Campus Beaulieu, Rennes, France
- INRIA, IRISA, GenOuest Core Facility, Campus de Beaulieu, Rennes, France
| | | | | | - Gaelen R Burke
- Department of Entomology, University of Georgia, Athens, Georgia, United States of America
| | - Rita Rebollo
- INRAE, INSA Lyon, BF2I, UMR203, Villeurbanne, France
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2
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Darmasaputra GS, van Rijnberk LM, Galli M. Functional consequences of somatic polyploidy in development. Development 2024; 151:dev202392. [PMID: 38415794 PMCID: PMC10946441 DOI: 10.1242/dev.202392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/29/2024]
Abstract
Polyploid cells contain multiple genome copies and arise in many animal tissues as a regulated part of development. However, polyploid cells can also arise due to cell division failure, DNA damage or tissue damage. Although polyploidization is crucial for the integrity and function of many tissues, the cellular and tissue-wide consequences of polyploidy can be very diverse. Nonetheless, many polyploid cell types and tissues share a remarkable similarity in function, providing important information about the possible contribution of polyploidy to cell and tissue function. Here, we review studies on polyploid cells in development, underlining parallel functions between different polyploid cell types, as well as differences between developmentally-programmed and stress-induced polyploidy.
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Affiliation(s)
- Gabriella S. Darmasaputra
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences and University Medical Center Utrecht, Uppsalalaan 8, 3584 CT, Utrecht, the Netherlands
| | - Lotte M. van Rijnberk
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences and University Medical Center Utrecht, Uppsalalaan 8, 3584 CT, Utrecht, the Netherlands
| | - Matilde Galli
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences and University Medical Center Utrecht, Uppsalalaan 8, 3584 CT, Utrecht, the Netherlands
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3
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Berg C, Sieber M, Sun J. Finishing the egg. Genetics 2024; 226:iyad183. [PMID: 38000906 PMCID: PMC10763546 DOI: 10.1093/genetics/iyad183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Accepted: 09/27/2023] [Indexed: 11/26/2023] Open
Abstract
Gamete development is a fundamental process that is highly conserved from early eukaryotes to mammals. As germ cells develop, they must coordinate a dynamic series of cellular processes that support growth, cell specification, patterning, the loading of maternal factors (RNAs, proteins, and nutrients), differentiation of structures to enable fertilization and ensure embryonic survival, and other processes that make a functional oocyte. To achieve these goals, germ cells integrate a complex milieu of environmental and developmental signals to produce fertilizable eggs. Over the past 50 years, Drosophila oogenesis has risen to the forefront as a system to interrogate the sophisticated mechanisms that drive oocyte development. Studies in Drosophila have defined mechanisms in germ cells that control meiosis, protect genome integrity, facilitate mRNA trafficking, and support the maternal loading of nutrients. Work in this system has provided key insights into the mechanisms that establish egg chamber polarity and patterning as well as the mechanisms that drive ovulation and egg activation. Using the power of Drosophila genetics, the field has begun to define the molecular mechanisms that coordinate environmental stresses and nutrient availability with oocyte development. Importantly, the majority of these reproductive mechanisms are highly conserved throughout evolution, and many play critical roles in the development of somatic tissues as well. In this chapter, we summarize the recent progress in several key areas that impact egg chamber development and ovulation. First, we discuss the mechanisms that drive nutrient storage and trafficking during oocyte maturation and vitellogenesis. Second, we examine the processes that regulate follicle cell patterning and how that patterning impacts the construction of the egg shell and the establishment of embryonic polarity. Finally, we examine regulatory factors that control ovulation, egg activation, and successful fertilization.
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Affiliation(s)
- Celeste Berg
- Department of Genome Sciences, University of Washington, Seattle, WA 98195-5065USA
| | - Matthew Sieber
- Department of Physiology, UT Southwestern Medical Center, Dallas, TX 75390USA
| | - Jianjun Sun
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, CT 06269USA
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Abstract
In this chapter, we highlight examples of the diverse array of developmental, cellular, and biochemical insights that can be gained by using Drosophila melanogaster oogenesis as a model tissue. We begin with an overview of ovary development and adult oogenesis. Then we summarize how the adult Drosophila ovary continues to advance our understanding of stem cells, cell cycle, cell migration, cytoplasmic streaming, nurse cell dumping, and cell death. We also review emerging areas of study, including the roles of lipid droplets, ribosomes, and nuclear actin in egg development. Finally, we conclude by discussing the growing conservation of processes and signaling pathways that regulate oogenesis and female reproduction from flies to humans.
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Reusswig KU, Bittmann J, Peritore M, Courtes M, Pardo B, Wierer M, Mann M, Pfander B. Unscheduled DNA replication in G1 causes genome instability and damage signatures indicative of replication collisions. Nat Commun 2022; 13:7014. [PMID: 36400763 PMCID: PMC9674678 DOI: 10.1038/s41467-022-34379-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Accepted: 10/24/2022] [Indexed: 11/19/2022] Open
Abstract
DNA replicates once per cell cycle. Interfering with the regulation of DNA replication initiation generates genome instability through over-replication and has been linked to early stages of cancer development. Here, we engineer genetic systems in budding yeast to induce unscheduled replication in a G1-like cell cycle state. Unscheduled G1 replication initiates at canonical S-phase origins. We quantifiy the composition of replisomes in G1- and S-phase and identified firing factors, polymerase α, and histone supply as factors that limit replication outside S-phase. G1 replication per se does not trigger cellular checkpoints. Subsequent replication during S-phase, however, results in over-replication and leads to chromosome breaks and chromosome-wide, strand-biased occurrence of RPA-bound single-stranded DNA, indicating head-to-tail replication collisions as a key mechanism generating genome instability upon G1 replication. Low-level, sporadic induction of G1 replication induces an identical response, indicating findings from synthetic systems are applicable to naturally occurring scenarios of unscheduled replication initiation.
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Affiliation(s)
- Karl-Uwe Reusswig
- grid.418615.f0000 0004 0491 845XDNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany ,grid.38142.3c000000041936754XPresent Address: Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA 02115 USA ,grid.65499.370000 0001 2106 9910Present Address: Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA 02215 USA
| | - Julia Bittmann
- grid.418615.f0000 0004 0491 845XDNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Martina Peritore
- grid.418615.f0000 0004 0491 845XDNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany ,grid.7551.60000 0000 8983 7915Present Address: Genome Maintenance Mechanisms in Health and Disease, Institute of Aerospace Medicine, German Aerospace Center (DLR), 51147 Cologne, Germany
| | - Mathilde Courtes
- grid.433120.7Institut de Génétique Humaine (IGH), Université de Montpellier – Centre National de la Recherche Scientifique, 34396 Montpellier, France
| | - Benjamin Pardo
- grid.433120.7Institut de Génétique Humaine (IGH), Université de Montpellier – Centre National de la Recherche Scientifique, 34396 Montpellier, France
| | - Michael Wierer
- grid.418615.f0000 0004 0491 845XProteomics and Signal Transduction, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany ,grid.5254.60000 0001 0674 042XPresent Address: Proteomics Research Infrastructure, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Matthias Mann
- grid.418615.f0000 0004 0491 845XProteomics and Signal Transduction, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Boris Pfander
- grid.418615.f0000 0004 0491 845XDNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany ,grid.7551.60000 0000 8983 7915Present Address: Genome Maintenance Mechanisms in Health and Disease, Institute of Aerospace Medicine, German Aerospace Center (DLR), 51147 Cologne, Germany ,grid.6190.e0000 0000 8580 3777Present Address: Genome Maintenance Mechanisms in Health and Disease, Institute of Genome Stability in Ageing and Disease, CECAD Research Center, University of Cologne, 50931 Cologne, Germany
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Su(Hw) primes 66D and 7F Drosophila chorion genes loci for amplification through chromatin decondensation. Sci Rep 2021; 11:16963. [PMID: 34417521 PMCID: PMC8379230 DOI: 10.1038/s41598-021-96488-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Accepted: 08/11/2021] [Indexed: 11/11/2022] Open
Abstract
Suppressor of Hairy wing [Su(Hw)] is an insulator protein that participates in regulating chromatin architecture and gene repression in Drosophila. In previous studies we have shown that Su(Hw) is also required for pre-replication complex (pre-RC) recruitment on Su(Hw)-bound sites (SBSs) in Drosophila S2 cells and pupa. Here, we describe the effect of Su(Hw) on developmentally regulated amplification of 66D and 7F Drosophila amplicons in follicle cells (DAFCs), widely used as models in replication studies. We show Su(Hw) binding co-localizes with all known DAFCs in Drosophila ovaries, whereas disruption of Su(Hw) binding to 66D and 7F DAFCs causes a two-fold decrease in the amplification of these loci. The complete loss of Su(Hw) binding to chromatin impairs pre-RC recruitment to all amplification regulatory regions of 66D and 7F loci at early oogenesis (prior to DAFCs amplification). These changes coincide with a considerable Su(Hw)-dependent condensation of chromatin at 66D and 7F loci. Although we observed the Brm, ISWI, Mi-2, and CHD1 chromatin remodelers at SBSs genome wide, their remodeler activity does not appear to be responsible for chromatin decondensation at the 66D and 7F amplification regulatory regions. We have discovered that, in addition to the CBP/Nejire and Chameau histone acetyltransferases, the Gcn5 acetyltransferase binds to 66D and 7F DAFCs at SBSs and this binding is dependent on Su(Hw). We propose that the main function of Su(Hw) in developmental amplification of 66D and 7F DAFCs is to establish a chromatin structure that is permissive to pre-RC recruitment.
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Yamamoto Y, Gustafson EA, Foulk MS, Smith HS, Gerbi SA. Anatomy and evolution of a DNA replication origin. Chromosoma 2021; 130:199-214. [PMID: 34254172 DOI: 10.1007/s00412-021-00756-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Revised: 01/09/2021] [Accepted: 03/09/2021] [Indexed: 10/20/2022]
Abstract
DNA amplification occurs at the DNA puff II/9A locus in the fungus fly Sciara coprophila. As a foundation to study the molecular mechanism for the initiating events of II/9A DNA re-replication, we have sequenced 14 kb spanning a DNase hypersensitive site (DHS) upstream of the 1 kb amplification origin and through transcription units II/9-1 and II/9-2 downstream of the origin. These elements are annotated as well as the ORC binding site at the origin and the transition point (TP) between continuous and discontinuous DNA syntheses that marks the origin of bidirectional replication at the nucleotide level. A 9 bp motif found at the TP is repeated near the other end of the 1 kb ORI and may identify a putative second TP. The steroid hormone ecdysone induces DNA amplification as well as transcription and puffing at locus II/9A. Within the 14 kb, several matches to the ecdysone response element (EcRE) consensus sequence were identified, including some in the amplification origin region. EcRE O-P is at a central axis of a remarkable symmetry, equidistant to the TPs that are themselves equidistant to EcRE O-1 and EcRE O-2. DNA sequence alterations have occurred throughout the II/9A region in a newly discovered polymorphism (#2). Polymorphism #2 is not specific to developmental stage, sex, or tissue, and it does not impair DNA amplification. The DHS, both 9 bp TP sequences, and EcREs O-1, O-P, and O-2 are conserved between the polymorphism #1 and #2 sequences, suggesting their functional importance and retention during evolutionary selection. Moreover, a 72 bp sequence in the Sciara DHS at DNA puff II/9A is conserved in DNA puff C-3 of Rhynchosciara americana. Comparisons are discussed between the Sciara II/9A amplicon and the chorion locus amplicon on the third chromosome of Drosophila.
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Affiliation(s)
- Yutaka Yamamoto
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University Division of Biology and Medicine, Box G - Sidney Frank Life Sciences Building room 260, Providence, RI, 02912, USA
| | - Eric A Gustafson
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University Division of Biology and Medicine, Box G - Sidney Frank Life Sciences Building room 260, Providence, RI, 02912, USA.,Zipher Medical Affairs Co., 380 Wareham Street, Marion, MA, 02738, USA
| | - Michael S Foulk
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University Division of Biology and Medicine, Box G - Sidney Frank Life Sciences Building room 260, Providence, RI, 02912, USA.,Department of Biology, Mercyhurst University, 501 East 38th Street, Erie, PA, 16546, USA
| | - Heidi S Smith
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University Division of Biology and Medicine, Box G - Sidney Frank Life Sciences Building room 260, Providence, RI, 02912, USA
| | - Susan A Gerbi
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University Division of Biology and Medicine, Box G - Sidney Frank Life Sciences Building room 260, Providence, RI, 02912, USA.
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Flynn JM, Long M, Wing RA, Clark AG. Evolutionary Dynamics of Abundant 7-bp Satellites in the Genome of Drosophila virilis. Mol Biol Evol 2021; 37:1362-1375. [PMID: 31960929 DOI: 10.1093/molbev/msaa010] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The factors that drive the rapid changes in abundance of tandem arrays of highly repetitive sequences, known as satellite DNA, are not well understood. Drosophila virilis has one of the highest relative amounts of simple satellites of any organism that has been studied, with an estimated >40% of its genome composed of a few related 7-bp satellites. Here, we use D. virilis as a model to understand technical biases affecting satellite sequencing and the evolutionary processes that drive satellite composition. By analyzing sequencing data from Illumina, PacBio, and Nanopore platforms, we identify platform-specific biases and suggest best practices for accurate characterization of satellites by sequencing. We use comparative genomics and cytogenetics to demonstrate that the highly abundant AAACTAC satellite family arose from a related satellite in the branch leading to the virilis phylad 4.5-11 Ma before exploding in abundance in some species of the clade. The most abundant satellite is conserved in sequence and location in the pericentromeric region but has diverged widely in abundance among species, whereas the satellites nearest the centromere are rapidly turning over in sequence composition. By analyzing multiple strains of D. virilis, we saw that the abundances of two centromere-proximal satellites are anticorrelated along a geographical gradient, which we suggest could be caused by ongoing conflicts at the centromere. In conclusion, we illuminate several key attributes of satellite evolutionary dynamics that we hypothesize to be driven by processes including selection, meiotic drive, and constraints on satellite sequence and abundance.
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Affiliation(s)
- Jullien M Flynn
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY
| | - Manyuan Long
- Department of Ecology and Evolution, University of Chicago, Chicago, IL
| | - Rod A Wing
- School of Plant Sciences, Arizona Genomics Institute, University of Arizona, Tucson, AZ
| | - Andrew G Clark
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY
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Armstrong RL, Das S, Hill CA, Duronio RJ, Nordman JT. Rif1 Functions in a Tissue-Specific Manner To Control Replication Timing Through Its PP1-Binding Motif. Genetics 2020; 215:75-87. [PMID: 32144132 PMCID: PMC7198277 DOI: 10.1534/genetics.120.303155] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Accepted: 03/05/2020] [Indexed: 12/19/2022] Open
Abstract
Replication initiation in eukaryotic cells occurs asynchronously throughout S phase, yielding early- and late-replicating regions of the genome, a process known as replication timing (RT). RT changes during development to ensure accurate genome duplication and maintain genome stability. To understand the relative contributions that cell lineage, cell cycle, and replication initiation regulators have on RT, we utilized the powerful developmental systems available in Drosophila melanogaster We generated and compared RT profiles from mitotic cells of different tissues and from mitotic and endocycling cells of the same tissue. Our results demonstrate that cell lineage has the largest effect on RT, whereas switching from a mitotic to an endoreplicative cell cycle has little to no effect on RT. Additionally, we demonstrate that the RT differences we observed in all cases are largely independent of transcriptional differences. We also employed a genetic approach in these same cell types to understand the relative contribution the eukaryotic RT control factor, Rif1, has on RT control. Our results demonstrate that Rif1 can function in a tissue-specific manner to control RT. Importantly, the Protein Phosphatase 1 (PP1) binding motif of Rif1 is essential for Rif1 to regulate RT. Together, our data support a model in which the RT program is primarily driven by cell lineage and is further refined by Rif1/PP1 to ultimately generate tissue-specific RT programs.
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Affiliation(s)
- Robin L Armstrong
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Souradip Das
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37232
| | - Christina A Hill
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Robert J Duronio
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina 27599
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, North Carolina 27599
- Department of Genetics, University of North Carolina, Chapel Hill, North Carolina 27599
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Jared T Nordman
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37232
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Wang XK, Wang QQ, Huang JL, Zhang LB, Zhou X, Liu JQ, Chen ZJ, Liao XW, Huang R, Yang CK, Zhu GZ, Han CY, Ye XP, Peng T. Novel candidate biomarkers of origin recognition complex 1, 5 and 6 for survival surveillance in patients with hepatocellular carcinoma. J Cancer 2020; 11:1869-1882. [PMID: 32194798 PMCID: PMC7052853 DOI: 10.7150/jca.39163] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Accepted: 12/20/2019] [Indexed: 01/02/2023] Open
Abstract
Background: Hepatocellular carcinoma (HCC) has high morbidity and mortality and lacks effective biomarkers for early diagnosis and survival surveillance. Origin recognition complex (ORC), consisting of ORC1-6 isoforms, was examined to assess the potential significance of ORC isoforms for HCC prognosis. Methods: Oncomine and Gene Expression Profiling Interactive Analysis (GEPIA) databases were used to examine differential isoform expression, stage-specific expression, calculate Pearson correlations and perform survival analysis. A human protein atlas database was utilized to evaluate the protein expression of ORCs in liver tissue. The cBioPortal database was used to assess isoform mutations and the survival significance of ORCs in HCC. Cytoscape software was employed to construct gene ontologies, metabolic pathways and gene-gene interaction networks. Results: Differential expression analysis indicated that ORC1 and ORC3-6 were highly expressed in tumor tissues in the Oncomine and GEPIA databases, while ORC2 was not. All the ORCs were showed positive and statistically significant correlations with each other (all P<0.001). ORC1-2 and ORC4-6 expressions were associated with disease stages I-IV (all P<0.05), but ORC3 was not. Survival analysis found that ORC1 and ORC4-6 expressions were associated with overall survival (OS), and ORC1-3 and ORC5-6 expression were associated with recurrence-free survival (RFS; all P<0.05). In addition, low expression of these ORC genes consistently indicated better prognosis compared with high expression. Protein expression analysis revealed that ORC1 and ORC3-6 were expressed in normal liver tissues, whereas ORC2 was not. Enrichment analysis indicated that ORCs were associated with DNA metabolic process, sequence-specific DNA binding and were involved in DNA replication, cell cycle, E2F-enabled inhibition of pre-replication complex formation and G1/S transition. Conclusions: Differentially expressed ORC1, 5 and 6 are candidate biomarkers for survival prediction and recurrence surveillance in HCC.
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Affiliation(s)
- Xiang-Kun Wang
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi Province, China
| | - Qiao-Qi Wang
- Department of Medical Cosmetology, The Second Affiliated Hospital of Guangxi Medical University, Nanning 530000, Guangxi Province, China
| | - Jian-Lu Huang
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi Province, China
- Department of Hepatobiliary Surgery, The Third Affiliated Hospital of Guangxi Medical University, Nanning 530031, Guangxi Province, China
| | - Lin-Bo Zhang
- Department of Health Management and Division of Physical Examination, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi Zhuang Autonomous Region, People's Republic of China
| | - Xin Zhou
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi Province, China
| | - Jun-Qi Liu
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi Province, China
| | - Zi-Jun Chen
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi Province, China
| | - Xi-Wen Liao
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi Province, China
| | - Rui Huang
- Department of Hematology, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi Province, China
| | - Cheng-Kun Yang
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi Province, China
| | - Guang-Zhi Zhu
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi Province, China
| | - Chuang-Ye Han
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi Province, China
| | - Xin-Ping Ye
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi Province, China
| | - Tao Peng
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, Guangxi Province, China
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Vorobyeva NE, Mazina MY. Functions of Insulators in the Context of Modern Whole-Genome Investigations. RUSS J GENET+ 2019. [DOI: 10.1134/s1022795419020170] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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12
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Velentzas AD, Velentzas PD, Katarachia SA, Anagnostopoulos AK, Sagioglou NE, Thanou EV, Tsioka MM, Mpakou VE, Kollia Z, Gavriil VE, Papassideri IS, Tsangaris GT, Cefalas AC, Sarantopoulou E, Stravopodis DJ. The indispensable contribution of s38 protein to ovarian-eggshell morphogenesis in Drosophila melanogaster. Sci Rep 2018; 8:16103. [PMID: 30382186 PMCID: PMC6208399 DOI: 10.1038/s41598-018-34532-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Accepted: 10/18/2018] [Indexed: 12/21/2022] Open
Abstract
Drosophila chorion represents a remarkable model system for the in vivo study of complex extracellular-matrix architectures. For its organization and structure, s38 protein is considered as a component of major importance, since it is synthesized and secreted during early choriogenesis. However, there is no evidence that proves its essential, or redundant, role in chorion biogenesis. Hence, we show that targeted downregulation of s38 protein, specifically in the ovarian follicle-cell compartment, via employment of an RNAi-mediated strategy, causes generation of diverse dysmorphic phenotypes, regarding eggshell’s regionally and radially specialized structures. Downregulation of s38 protein severely impairs fly’s fertility and is unable to be compensated by the s36 homologous family member, thus unveiling s38 protein’s essential contribution to chorion’s assembly and function. Altogether, s38 acts as a key skeletal protein being critically implicated in the patterning establishment of a highly structured tripartite endochorion. Furthermore, it seems that s38 loss may sensitize choriogenesis to stochastic variation in its coordination and timing.
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Affiliation(s)
- Athanassios D Velentzas
- Section of Cell Biology and Biophysics, Department of Biology, School of Science, National and Kapodistrian University of Athens (NKUA), Athens, Greece
| | - Panagiotis D Velentzas
- Section of Cell Biology and Biophysics, Department of Biology, School of Science, National and Kapodistrian University of Athens (NKUA), Athens, Greece.,Department of Cancer Biology, Medical School, University of Massachusetts, Worcester, Massachusetts (MA), USA
| | - Stamatia A Katarachia
- Section of Cell Biology and Biophysics, Department of Biology, School of Science, National and Kapodistrian University of Athens (NKUA), Athens, Greece
| | | | - Niki E Sagioglou
- Section of Cell Biology and Biophysics, Department of Biology, School of Science, National and Kapodistrian University of Athens (NKUA), Athens, Greece
| | - Eleni V Thanou
- Section of Cell Biology and Biophysics, Department of Biology, School of Science, National and Kapodistrian University of Athens (NKUA), Athens, Greece
| | - Maria M Tsioka
- Section of Cell Biology and Biophysics, Department of Biology, School of Science, National and Kapodistrian University of Athens (NKUA), Athens, Greece
| | - Vassiliki E Mpakou
- Section of Cell Biology and Biophysics, Department of Biology, School of Science, National and Kapodistrian University of Athens (NKUA), Athens, Greece
| | - Zoe Kollia
- Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation (NHRF), Athens, Greece
| | - Vassilios E Gavriil
- Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation (NHRF), Athens, Greece
| | - Issidora S Papassideri
- Section of Cell Biology and Biophysics, Department of Biology, School of Science, National and Kapodistrian University of Athens (NKUA), Athens, Greece
| | - George Th Tsangaris
- Systems Biology Center, Biomedical Research Foundation of the Academy of Athens (BRFAA), Athens, Greece
| | | | - Evangelia Sarantopoulou
- Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation (NHRF), Athens, Greece
| | - Dimitrios J Stravopodis
- Section of Cell Biology and Biophysics, Department of Biology, School of Science, National and Kapodistrian University of Athens (NKUA), Athens, Greece.
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13
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Krasnov AN, Vorobyova NE, Mazina MY. Insulator Protein Su(Hw) Is Indispensable for Amplification of Part of Drosophila Amplicons in Follicular Cells (DAFCs) during Early Oogenesis. DOKL BIOCHEM BIOPHYS 2018; 479:80-82. [PMID: 29779102 DOI: 10.1134/s1607672918020059] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Indexed: 11/23/2022]
Abstract
We found that the Su(Hw) insulator protein binds to all known Drosophila amplicons in follicular cells (DAFCs). Su(Hw) binding is required for ORC replication complex positioning on part of DAFCs during early oogenesis. Our data allow us to expand the current view on the role of the Su(Hw) protein in Drosophila oogenesis as a transcription repressor. We assume that Su(Hw) is involved in the coordination of transcription and replication processes during oogenesis in Drosophila.
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Affiliation(s)
- A N Krasnov
- Institute of Gene Biology, Russian Academy of Sciences, Moscow, 119334, Russia
| | - N E Vorobyova
- Institute of Gene Biology, Russian Academy of Sciences, Moscow, 119334, Russia
| | - M Yu Mazina
- Institute of Gene Biology, Russian Academy of Sciences, Moscow, 119334, Russia.
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14
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Landskron L, Steinmann V, Bonnay F, Burkard TR, Steinmann J, Reichardt I, Harzer H, Laurenson AS, Reichert H, Knoblich JA. The asymmetrically segregating lncRNA cherub is required for transforming stem cells into malignant cells. eLife 2018; 7:31347. [PMID: 29580384 PMCID: PMC5871330 DOI: 10.7554/elife.31347] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 02/06/2018] [Indexed: 12/20/2022] Open
Abstract
Tumor cells display features that are not found in healthy cells. How they become immortal and how their specific features can be exploited to combat tumorigenesis are key questions in tumor biology. Here we describe the long non-coding RNA cherub that is critically required for the development of brain tumors in Drosophila but is dispensable for normal development. In mitotic Drosophila neural stem cells, cherub localizes to the cell periphery and segregates into the differentiating daughter cell. During tumorigenesis, de-differentiation of cherub-high cells leads to the formation of tumorigenic stem cells that accumulate abnormally high cherub levels. We show that cherub establishes a molecular link between the RNA-binding proteins Staufen and Syncrip. As Syncrip is part of the molecular machinery specifying temporal identity in neural stem cells, we propose that tumor cells proliferate indefinitely, because cherub accumulation no longer allows them to complete their temporal neurogenesis program. Many biological signals control how cells grow and divide. However, cancer cells do not obey these growth-restricting signals, and as a result large tumors may develop. Recent experiments have suggested that stem cells – the precursors to the different types of specialized cells found in the body – are particularly important for generating tumors. A stem cell normally divides unequally to form a self-renewing cell and a more specialized cell (often a progenitor cell that will give rise to increasingly specialized cell types). The timing of when the specialization occurs can be key to guiding the ultimately produced cell progenies to their final identity. However, in a tumor cells can retain the ability to self-renew. Ultimately, the resulting ‘tumor stem cells’ become immortal and proliferate indefinitely. It is not fully understood why this uncontrolled proliferation occurs. Just like mammals (including humans), fruit flies can develop tumors. Some of the DNA mutations responsible for tumor development were already identified in flies as early as in the 1970s. This has made fruit flies a well-studied model system for uncovering the principle defects that cause tumors to form. Landskron et al. have now studied the neural stem cells found in brain tumors in fruit flies. Additional DNA mutations were not responsible for these cells becoming immortal. Instead, certain RNA molecules – products that are ‘transcribed’ from the DNA – were present in different amounts in tumor cells. The RNA that showed the greatest increase in tumor cells is a so-called long non-coding RNA named cherub. This RNA molecule has no important role in normal fruit flies, but is critical for tumor formation. Landskron et al. found that during cell division cherub segregates from the neural stem cells to the newly formed progenitor cells, where it breaks down over time. Progenitor cells that contain high levels of cherub give rise to tumor-generating neural stem cells. At the molecular level, cherubhelps two proteins to interact with each other: one called Syncrip that makes the neural stem cells take on a older identity, and another one (Staufen) that tethers it to the cell membrane. By restricting Syncrip to a particular location in the cell, cherub alters the timing of stem cell specialization, which contributes to tumor formation. Overall, the results presented by Landskron et al. reveal a new role for long non-coding RNAs: controlling the localization of the proteins that determine the fate of the cell. They also highlight a critical link between the timing of stem cell development and the proliferation of the cells. Further work is now needed to test whether the same control mechanism works in species other than fruit flies.
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Affiliation(s)
- Lisa Landskron
- IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna, Austria
| | - Victoria Steinmann
- IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna, Austria
| | - Francois Bonnay
- IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna, Austria
| | - Thomas R Burkard
- IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna, Austria
| | - Jonas Steinmann
- IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna, Austria
| | - Ilka Reichardt
- IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna, Austria
| | - Heike Harzer
- IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna, Austria
| | | | | | - Jürgen A Knoblich
- IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna, Austria
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15
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DNA Replication Control During Drosophila Development: Insights into the Onset of S Phase, Replication Initiation, and Fork Progression. Genetics 2017; 207:29-47. [PMID: 28874453 PMCID: PMC5586379 DOI: 10.1534/genetics.115.186627] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 05/19/2017] [Indexed: 12/11/2022] Open
Abstract
Proper control of DNA replication is critical to ensure genomic integrity during cell proliferation. In addition, differential regulation of the DNA replication program during development can change gene copy number to influence cell size and gene expression. Drosophila melanogaster serves as a powerful organism to study the developmental control of DNA replication in various cell cycle contexts in a variety of differentiated cell and tissue types. Additionally, Drosophila has provided several developmentally regulated replication models to dissect the molecular mechanisms that underlie replication-based copy number changes in the genome, which include differential underreplication and gene amplification. Here, we review key findings and our current understanding of the developmental control of DNA replication in the contexts of the archetypal replication program as well as of underreplication and differential gene amplification. We focus on the use of these latter two replication systems to delineate many of the molecular mechanisms that underlie the developmental control of replication initiation and fork elongation.
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16
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Stormo BM, Fox DT. Polyteny: still a giant player in chromosome research. Chromosome Res 2017; 25:201-214. [PMID: 28779272 PMCID: PMC5768140 DOI: 10.1007/s10577-017-9562-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Revised: 07/19/2017] [Accepted: 07/21/2017] [Indexed: 12/17/2022]
Abstract
In this era of high-resolution mapping of chromosome territories, topological interactions, and chromatin states, it is increasingly appreciated that the positioning of chromosomes and their interactions within the nucleus is critical for cellular function. Due to their large size and distinctive structure, polytene chromosomes have contributed a wealth of knowledge regarding chromosome regulation. In this review, we discuss the diversity of polytene chromosomes in nature and in disease, examine the recurring structural features of polytene chromosomes in terms of what they reveal about chromosome biology, and discuss recent advances regarding how polytene chromosomes are assembled and disassembled. After over 130 years of study, these giant chromosomes are still powerful tools to understand chromosome biology.
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Affiliation(s)
- Benjamin M Stormo
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, 27710, USA
| | - Donald T Fox
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, 27710, USA.
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17
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Abstract
Replication forks encounter obstacles that must be repaired or bypassed to complete chromosome duplication before cell division. Proteomic analysis of replication forks suggests that the checkpoint and repair machinery travels with unperturbed forks, implying that they are poised to respond to stalling and collapse. However, impaired fork progression still generates aberrations, including repeat copy number instability and chromosome rearrangements. Deregulated origin firing also causes fork instability if a newer fork collides with an older one, generating double-strand breaks (DSBs) and partially rereplicated DNA. Current evidence suggests that multiple mechanisms are used to repair rereplication damage, yet these can have deleterious consequences for genome integrity.
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18
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Choi SH, Park JH, Nguyen TTN, Shim HJ, Song YH. Initiation of Drosophila chorion gene amplification requires Claspin and mus101, whereas Claspin, but not mus101, plays a major role during elongation. Dev Dyn 2017; 246:466-474. [PMID: 28294450 PMCID: PMC5435936 DOI: 10.1002/dvdy.24499] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Revised: 02/25/2017] [Accepted: 03/02/2017] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND Claspin and TopBP1 are checkpoint mediators that are required for the phosphorylation of Chk1 by ATR to maintain genomic stability. Here, we investigated the functions of Drosophila Claspin and mus101 (TopBP1 ortholog) during chorion (eggshell component) gene amplification, which occurs in follicle cells in the absence of global genomic DNA replication. RESULTS Unlike Drosophila mei-41 (ATR ortholog) mutant embryos, Claspin and mus101 mutant embryos showed severe eggshell defects resulting from defects in chorion gene amplification. EdU (5-ethynyl-2'-deoxyuridine) incorporation assay during initiation and elongation stages revealed that Claspin and mus101 were required for initiation, while only Claspin had a major role in the efficient progression of the replication forks. Claspin proteins were enriched in the amplification foci both in the initiation and elongation stage-follicle cell nuclei in a mei-41-independent manner. The focal localization of ORC2, a component of the origin recognition complex, was not significantly affected in the Claspin mutant, whereas it was reduced in the mus101 mutant. CONCLUSIONS Drosophila Claspin plays a major role in the initiation and elongation stages of chorion gene amplification by localizing to the amplification foci in a mei-41-independent manner. Drosophila mus101 is also involved in chorion gene amplification, mostly functioning in initiation, rather than elongation. Developmental Dynamics 246:466-474, 2016. © 2017 The Authors Developmental Dynamics published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists.
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Affiliation(s)
- Seung Ho Choi
- Ilsong Institute of Life Science, Hallym University, Anyang, Gyeonggi-do, Republic of Korea
| | - Ji-Hong Park
- Department of Biomedical Gerontology, Hallym University, Chuncheon, Gangwon-do, Republic of Korea
| | - Tram Thi Ngoc Nguyen
- Department of Biomedical Gerontology, Hallym University, Chuncheon, Gangwon-do, Republic of Korea
| | - Hee Jin Shim
- Ilsong Institute of Life Science, Hallym University, Anyang, Gyeonggi-do, Republic of Korea
| | - Young-Han Song
- Ilsong Institute of Life Science, Hallym University, Anyang, Gyeonggi-do, Republic of Korea.,Department of Biomedical Gerontology, Hallym University, Chuncheon, Gangwon-do, Republic of Korea
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19
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Multiple mechanisms contribute to double-strand break repair at rereplication forks in Drosophila follicle cells. Proc Natl Acad Sci U S A 2016; 113:13809-13814. [PMID: 27849606 DOI: 10.1073/pnas.1617110113] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Rereplication generates double-strand breaks (DSBs) at sites of fork collisions and causes genomic damage, including repeat instability and chromosomal aberrations. However, the primary mechanism used to repair rereplication DSBs varies across different experimental systems. In Drosophila follicle cells, developmentally regulated rereplication is used to amplify six genomic regions, two of which contain genes encoding eggshell proteins. We have exploited this system to test the roles of several DSB repair pathways during rereplication, using fork progression as a readout for DSB repair efficiency. Here we show that a null mutation in the microhomology-mediated end-joining (MMEJ) component, polymerase θ/mutagen-sensitive 308 (mus308), exhibits a sporadic thin eggshell phenotype and reduced chorion gene expression. Unlike other thin eggshell mutants, mus308 displays normal origin firing but reduced fork progression at two regions of rereplication. We also find that MMEJ compensates for loss of nonhomologous end joining to repair rereplication DSBs in a site-specific manner. Conversely, we show that fork progression is enhanced in the absence of both Drosophila Rad51 homologs, spindle-A and spindle-B, revealing homologous recombination is active and actually impairs fork movement during follicle cell rereplication. These results demonstrate that several DSB repair pathways are used during rereplication in the follicle cells and their contribution to productive fork progression is influenced by genomic position and repair pathway competition. Furthermore, our findings illustrate that specific rereplication DSB repair pathways can have major effects on cellular physiology, dependent upon genomic context.
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20
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Simon CR, Siviero F, Monesi N. Beyond DNA puffs: What can we learn from studying sciarids? Genesis 2016; 54:361-78. [PMID: 27178805 DOI: 10.1002/dvg.22946] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Revised: 05/11/2016] [Accepted: 05/12/2016] [Indexed: 11/07/2022]
Abstract
Members of the Sciaridae family attracted the interest of researchers because of the demonstration that the DNA puff regions, which are formed in the salivary gland polytene chromosomes at the end of the fourth larval instar, constitute sites of developmentally regulated gene amplification. Besides contributing to a deeper understanding of the process of gene amplification, the study of sciarids has also provided important insights on other biological processes such as sex determination, programmed cell death, insect immunity, telomere maintenance, and nucleolar organizing regions (NOR) formation. Open questions in sciarids include among others, early development, the role of noncoding RNAs in gene amplification and the relationship between gene amplification and transcription in DNA puff forming regions. These and other questions can now be pursued with next generation sequencing techniques and experiments using RNAi experiments, since this latter technique has been shown to be feasible in sciarids. These new perspectives in the field of sciarid biology open the opportunity to consolidate sciarid species as important emerging models. genesis 54:361-378, 2016. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Claudio Roberto Simon
- Departamento de Biologia Estrutural, Universidade Federal do Triângulo Mineiro-UFTM, Instituto de Ciências Biológicas e Naturais, Uberaba, MG, Brazil, CEP 38025-015
| | - Fábio Siviero
- Departamento de Biologia Celular e do Desenvolvimento, Universidade de São Paulo, Instituto de Ciências Biomédicas, São Paulo, SP, Brazil, CEP 05508-900
| | - Nadia Monesi
- Departamento de Análises Clínicas, Toxicológicas e Bromatológicas, Universidade de São Paulo, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Ribeirão Preto, SP, Brazil
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21
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The Histone Variant H3.3 Is Enriched at Drosophila Amplicon Origins but Does Not Mark Them for Activation. G3-GENES GENOMES GENETICS 2016; 6:1661-71. [PMID: 27172191 PMCID: PMC4889662 DOI: 10.1534/g3.116.028068] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Eukaryotic DNA replication begins from multiple origins. The origin recognition complex (ORC) binds origin DNA and scaffolds assembly of a prereplicative complex (pre-RC), which is subsequently activated to initiate DNA replication. In multicellular eukaryotes, origins do not share a strict DNA consensus sequence, and their activity changes in concert with chromatin status during development, but mechanisms are ill-defined. Previous genome-wide analyses in Drosophila and other organisms have revealed a correlation between ORC binding sites and the histone variant H3.3. This correlation suggests that H3.3 may designate origin sites, but this idea has remained untested. To address this question, we examined the enrichment and function of H3.3 at the origins responsible for developmental gene amplification in the somatic follicle cells of the Drosophila ovary. We found that H3.3 is abundant at these amplicon origins. H3.3 levels remained high when replication initiation was blocked, indicating that H3.3 is abundant at the origins before activation of the pre-RC. H3.3 was also enriched at the origins during early oogenesis, raising the possibility that H3.3 bookmarks sites for later amplification. However, flies null mutant for both of the H3.3 genes in Drosophila did not have overt defects in developmental gene amplification or genomic replication, suggesting that H3.3 is not essential for the assembly or activation of the pre-RC at origins. Instead, our results imply that the correlation between H3.3 and ORC sites reflects other chromatin attributes that are important for origin function.
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22
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Kopytova D, Popova V, Kurshakova M, Shidlovskii Y, Nabirochkina E, Brechalov A, Georgiev G, Georgieva S. ORC interacts with THSC/TREX-2 and its subunits promote Nxf1 association with mRNP and mRNA export in Drosophila. Nucleic Acids Res 2016; 44:4920-33. [PMID: 27016737 PMCID: PMC4889942 DOI: 10.1093/nar/gkw192] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 03/11/2016] [Indexed: 12/20/2022] Open
Abstract
The origin recognition complex (ORC) of eukaryotes associates with the replication origins and initiates the pre-replication complex assembly. In the literature, there are several reports of interaction of ORC with different RNAs. Here, we demonstrate for the first time a direct interaction of ORC with the THSC/TREX-2 mRNA nuclear export complex. The THSC/TREX-2 was purified from the Drosophila embryonic extract and found to bind with a fraction of the ORC. This interaction occurred via several subunits and was essential for Drosophila viability. Also, ORC was associated with mRNP, which was facilitated by TREX-2. ORC subunits interacted with the Nxf1 receptor mediating the bulk mRNA export. The knockdown of Orc5 led to a drop in the Nxf1 association with mRNP, while Orc3 knockdown increased the level of mRNP-bound Nxf1. The knockdown of Orc5, Orc3 and several other ORC subunits led to an accumulation of mRNA in the nucleus, suggesting that ORC participates in the regulation of the mRNP export.
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Affiliation(s)
- Daria Kopytova
- Institute of Gene Biology, Russian Academy of Sciences, Moscow 119334, Russia
| | - Varvara Popova
- Institute of Gene Biology, Russian Academy of Sciences, Moscow 119334, Russia
| | - Maria Kurshakova
- Institute of Gene Biology, Russian Academy of Sciences, Moscow 119334, Russia
| | - Yulii Shidlovskii
- Institute of Gene Biology, Russian Academy of Sciences, Moscow 119334, Russia
| | - Elena Nabirochkina
- Institute of Gene Biology, Russian Academy of Sciences, Moscow 119334, Russia
| | - Alexander Brechalov
- Institute of Gene Biology, Russian Academy of Sciences, Moscow 119334, Russia
| | - Georgii Georgiev
- Institute of Gene Biology, Russian Academy of Sciences, Moscow 119334, Russia
| | - Sofia Georgieva
- Institute of Gene Biology, Russian Academy of Sciences, Moscow 119334, Russia
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23
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Sokolowski TR, Walczak AM, Bialek W, Tkačik G. Extending the dynamic range of transcription factor action by translational regulation. Phys Rev E 2016; 93:022404. [PMID: 26986359 PMCID: PMC5221721 DOI: 10.1103/physreve.93.022404] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Indexed: 11/07/2022]
Abstract
A crucial step in the regulation of gene expression is binding of transcription factor (TF) proteins to regulatory sites along the DNA. But transcription factors act at nanomolar concentrations, and noise due to random arrival of these molecules at their binding sites can severely limit the precision of regulation. Recent work on the optimization of information flow through regulatory networks indicates that the lower end of the dynamic range of concentrations is simply inaccessible, overwhelmed by the impact of this noise. Motivated by the behavior of homeodomain proteins, such as the maternal morphogen Bicoid in the fruit fly embryo, we suggest a scheme in which transcription factors also act as indirect translational regulators, binding to the mRNA of other regulatory proteins. Intuitively, each mRNA molecule acts as an independent sensor of the input concentration, and averaging over these multiple sensors reduces the noise. We analyze information flow through this scheme and identify conditions under which it outperforms direct transcriptional regulation. Our results suggest that the dual role of homeodomain proteins is not just a historical accident, but a solution to a crucial physics problem in the regulation of gene expression.
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Affiliation(s)
- Thomas R. Sokolowski
- Institute of Science and Technology Austria, Am Campus 1, A-3400
Klosterneuburg, Austria
| | - Aleksandra M. Walczak
- CNRS-Laboratoire de Physique Théorique de
l’École Normale Supérieure, 24 rue Lhomond, F-75005 Paris,
France
| | - William Bialek
- Joseph Henry Laboratories of Physics, Lewis-Sigler Institute for
Integrative Genomics, Princeton University Princeton, New Jersey 08544, USA
| | - Gašper Tkačik
- Institute of Science and Technology Austria, Am Campus 1, A-3400
Klosterneuburg, Austria
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24
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Selective Amplification of the Genome Surrounding Key Placental Genes in Trophoblast Giant Cells. Curr Biol 2016; 26:230-236. [PMID: 26774788 DOI: 10.1016/j.cub.2015.11.060] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Revised: 10/10/2015] [Accepted: 11/16/2015] [Indexed: 12/23/2022]
Abstract
While most cells maintain a diploid state, polyploid cells exist in many organisms and are particularly prevalent within the mammalian placenta [1], where they can generate more than 900 copies of the genome [2]. Polyploidy is thought to be an efficient method of increasing the content of the genome by avoiding the costly and slow process of cytokinesis [1, 3, 4]. Polyploidy can also affect gene regulation by amplifying a subset of genomic regions required for specific cellular function [1, 3, 4]. This mechanism is found in the fruit fly Drosophila melanogaster, where polyploid ovarian follicle cells amplify genomic regions containing chorion genes, which facilitate secretion of eggshell proteins [5]. Here, we report that genomic amplification also occurs in mammals at selective regions of the genome in parietal trophoblast giant cells (p-TGCs) of the mouse placenta. Using whole-genome sequencing (WGS) and digital droplet PCR (ddPCR) of mouse p-TGCs, we identified five amplified regions, each containing a gene family known to be involved in mammalian placentation: the prolactins (two clusters), serpins, cathepsins, and the natural killer (NK)/C-type lectin (CLEC) complex [6-12]. We report here the first description of amplification at selective genomic regions in mammals and present evidence that this is an important mode of genome regulation in placental TGCs.
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25
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Abstract
Dividing cells that experience chromosome mis-segregation generate aneuploid daughter cells, which contain an incorrect number of chromosomes. Although aneuploidy interferes with the proliferation of untransformed cells, it is also, paradoxically, a hallmark of cancer, a disease defined by increased proliferative potential. These contradictory effects are also observed in mouse models of chromosome instability (CIN). CIN can inhibit and promote tumorigenesis. Recent work has provided insights into the cellular consequences of CIN and aneuploidy. Chromosome mis-segregation per se can alter the genome in many more ways than just causing the gain or loss of chromosomes. The short- and long-term effects of aneuploidy are caused by gene-specific effects and a stereotypic aneuploidy stress response. Importantly, these recent findings provide insights into the role of aneuploidy in tumorigenesis.
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26
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Abstract
DNA replication begins with the assembly of pre-replication complexes (pre-RCs) at thousands of DNA replication origins during the G1 phase of the cell cycle. At the G1-S-phase transition, pre-RCs are converted into pre-initiation complexes, in which the replicative helicase is activated, leading to DNA unwinding and initiation of DNA synthesis. However, only a subset of origins are activated during any S phase. Recent insights into the mechanisms underlying this choice reveal how flexibility in origin usage and temporal activation are linked to chromosome structure and organization, cell growth and differentiation, and replication stress.
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27
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Liu J, Zimmer K, Rusch DB, Paranjape N, Podicheti R, Tang H, Calvi BR. DNA sequence templates adjacent nucleosome and ORC sites at gene amplification origins in Drosophila. Nucleic Acids Res 2015; 43:8746-61. [PMID: 26227968 PMCID: PMC4605296 DOI: 10.1093/nar/gkv766] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 07/16/2015] [Indexed: 12/12/2022] Open
Abstract
Eukaryotic origins of DNA replication are bound by the origin recognition complex (ORC), which scaffolds assembly of a pre-replicative complex (pre-RC) that is then activated to initiate replication. Both pre-RC assembly and activation are strongly influenced by developmental changes to the epigenome, but molecular mechanisms remain incompletely defined. We have been examining the activation of origins responsible for developmental gene amplification in Drosophila. At a specific time in oogenesis, somatic follicle cells transition from genomic replication to a locus-specific replication from six amplicon origins. Previous evidence indicated that these amplicon origins are activated by nucleosome acetylation, but how this affects origin chromatin is unknown. Here, we examine nucleosome position in follicle cells using micrococcal nuclease digestion with Ilumina sequencing. The results indicate that ORC binding sites and other essential origin sequences are nucleosome-depleted regions (NDRs). Nucleosome position at the amplicons was highly similar among developmental stages during which ORC is or is not bound, indicating that being an NDR is not sufficient to specify ORC binding. Importantly, the data suggest that nucleosomes and ORC have opposite preferences for DNA sequence and structure. We propose that nucleosome hyperacetylation promotes pre-RC assembly onto adjacent DNA sequences that are disfavored by nucleosomes but favored by ORC.
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Affiliation(s)
- Jun Liu
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Kurt Zimmer
- School of Informatics and Computing, Indiana University, Bloomington, IN 47405, USA
| | - Douglas B Rusch
- Center for Genomics and Bioinformatics, Indiana University, Bloomington, IN 47405, USA
| | - Neha Paranjape
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Ram Podicheti
- School of Informatics and Computing, Indiana University, Bloomington, IN 47405, USA Center for Genomics and Bioinformatics, Indiana University, Bloomington, IN 47405, USA
| | - Haixu Tang
- School of Informatics and Computing, Indiana University, Bloomington, IN 47405, USA
| | - Brian R Calvi
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
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Alexander JL, Barrasa MI, Orr-Weaver TL. Replication fork progression during re-replication requires the DNA damage checkpoint and double-strand break repair. Curr Biol 2015; 25:1654-60. [PMID: 26051888 DOI: 10.1016/j.cub.2015.04.058] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 03/02/2015] [Accepted: 04/24/2015] [Indexed: 11/19/2022]
Abstract
Replication origins are under tight regulation to ensure activation occurs only once per cell cycle [1, 2]. Origin re-firing in a single S phase leads to the generation of DNA double-strand breaks (DSBs) and activation of the DNA damage checkpoint [2-7]. If the checkpoint is blocked, cells enter mitosis with partially re-replicated DNA that generates chromosome breaks and fusions [5]. These types of chromosomal aberrations are common in numerous human cancers, suggesting that re-replication events contribute to cancer progression. It was proposed that fork instability and DSBs formed during re-replication are the result of head-to-tail collisions and collapse of adjacent replication forks [3]. However, previously studied systems lack the resolution to determine whether the observed DSBs are generated at sites of fork collisions. Here, we utilize the Drosophila ovarian follicle cells, which exhibit re-replication under precise developmental control [8-10], to model the consequences of re-replication at actively elongating forks. Re-replication occurs from specific replication origins at six genomic loci, termed Drosophila amplicons in follicle cells (DAFCs) [10-12]. Precise developmental timing of DAFC origin firing permits identification of forks at defined points after origin initiation [13, 14]. Here, we show that DAFC re-replication causes fork instability and generates DSBs at sites of potential fork collisions. Immunofluorescence and ChIP-seq demonstrate the DSB marker γH2Av is enriched at elongating forks. Fork progression is reduced in the absence of DNA damage checkpoint components and nonhomologous end-joining (NHEJ), but not homologous recombination. NHEJ appears to continually repair forks during re-replication to maintain elongation.
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Affiliation(s)
- Jessica L Alexander
- Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, 68-132, Cambridge, MA 02139, USA
| | - M Inmaculada Barrasa
- Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, MA 02142, USA
| | - Terry L Orr-Weaver
- Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, 68-132, Cambridge, MA 02139, USA.
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29
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Urban JM, Foulk MS, Casella C, Gerbi SA. The hunt for origins of DNA replication in multicellular eukaryotes. F1000PRIME REPORTS 2015; 7:30. [PMID: 25926981 PMCID: PMC4371235 DOI: 10.12703/p7-30] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Origins of DNA replication (ORIs) occur at defined regions in the genome. Although DNA sequence defines the position of ORIs in budding yeast, the factors for ORI specification remain elusive in metazoa. Several methods have been used recently to map ORIs in metazoan genomes with the hope that features for ORI specification might emerge. These methods are reviewed here with analysis of their advantages and shortcomings. The various factors that may influence ORI selection for initiation of DNA replication are discussed.
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Affiliation(s)
- John M. Urban
- Division of Biology and Medicine, Department of Molecular Biology, Cell Biology and Biochemistry, Brown UniversitySidney Frank Hall, 185 Meeting Street, Providence, RI 02912USA
| | - Michael S. Foulk
- Division of Biology and Medicine, Department of Molecular Biology, Cell Biology and Biochemistry, Brown UniversitySidney Frank Hall, 185 Meeting Street, Providence, RI 02912USA
- Department of Biology, Mercyhurst University501 East 38th Street, Erie, PA 16546USA
| | - Cinzia Casella
- Division of Biology and Medicine, Department of Molecular Biology, Cell Biology and Biochemistry, Brown UniversitySidney Frank Hall, 185 Meeting Street, Providence, RI 02912USA
- Institute for Molecular Medicine, University of Southern DenmarkJB Winsloews Vej 25, 5000 Odense CDenmark
| | - Susan A. Gerbi
- Division of Biology and Medicine, Department of Molecular Biology, Cell Biology and Biochemistry, Brown UniversitySidney Frank Hall, 185 Meeting Street, Providence, RI 02912USA
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30
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Ma Y, Kanakousaki K, Buttitta L. How the cell cycle impacts chromatin architecture and influences cell fate. Front Genet 2015; 6:19. [PMID: 25691891 PMCID: PMC4315090 DOI: 10.3389/fgene.2015.00019] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 01/14/2015] [Indexed: 01/17/2023] Open
Abstract
Since the earliest observations of cells undergoing mitosis, it has been clear that there is an intimate relationship between the cell cycle and nuclear chromatin architecture. The nuclear envelope and chromatin undergo robust assembly and disassembly during the cell cycle, and transcriptional and post-transcriptional regulation of histone biogenesis and chromatin modification is controlled in a cell cycle-dependent manner. Chromatin binding proteins and chromatin modifications in turn influence the expression of critical cell cycle regulators, the accessibility of origins for DNA replication, DNA repair, and cell fate. In this review we aim to provide an integrated discussion of how the cell cycle machinery impacts nuclear architecture and vice-versa. We highlight recent advances in understanding cell cycle-dependent histone biogenesis and histone modification deposition, how cell cycle regulators control histone modifier activities, the contribution of chromatin modifications to origin firing for DNA replication, and newly identified roles for nucleoporins in regulating cell cycle gene expression, gene expression memory and differentiation. We close with a discussion of how cell cycle status may impact chromatin to influence cell fate decisions, under normal contexts of differentiation as well as in instances of cell fate reprogramming.
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Affiliation(s)
- Yiqin Ma
- Department of Molecular, Cellular and Developmental Biology, University of Michigan , Ann Arbor, MI, USA
| | - Kiriaki Kanakousaki
- Department of Molecular, Cellular and Developmental Biology, University of Michigan , Ann Arbor, MI, USA
| | - Laura Buttitta
- Department of Molecular, Cellular and Developmental Biology, University of Michigan , Ann Arbor, MI, USA
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31
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Nordman JT, Kozhevnikova EN, Verrijzer CP, Pindyurin AV, Andreyeva EN, Shloma VV, Zhimulev IF, Orr-Weaver TL. DNA copy-number control through inhibition of replication fork progression. Cell Rep 2014; 9:841-9. [PMID: 25437540 DOI: 10.1016/j.celrep.2014.10.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 08/29/2014] [Accepted: 09/30/2014] [Indexed: 01/15/2023] Open
Abstract
Proper control of DNA replication is essential to ensure faithful transmission of genetic material and prevent chromosomal aberrations that can drive cancer progression and developmental disorders. DNA replication is regulated primarily at the level of initiation and is under strict cell-cycle regulation. Importantly, DNA replication is highly influenced by developmental cues. In Drosophila, specific regions of the genome are repressed for DNA replication during differentiation by the SNF2 domain-containing protein SUUR through an unknown mechanism. We demonstrate that SUUR is recruited to active replication forks and mediates the repression of DNA replication by directly inhibiting replication fork progression instead of functioning as a replication fork barrier. Mass spectrometry identification of SUUR-associated proteins identified the replicative helicase member CDC45 as a SUUR-associated protein, supporting a role for SUUR directly at replication forks. Our results reveal that control of eukaryotic DNA copy number can occur through the inhibition of replication fork progression.
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Affiliation(s)
- Jared T Nordman
- Whitehead Institute and Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142, USA
| | - Elena N Kozhevnikova
- Erasmus University Medical Centre, P.O. Box 1738, 3000 DR Rotterdam, the Netherlands; Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Lavrentyev Avenue 10, Novosibirsk 630090, Russia
| | - C Peter Verrijzer
- Erasmus University Medical Centre, P.O. Box 1738, 3000 DR Rotterdam, the Netherlands
| | - Alexey V Pindyurin
- Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands; Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, Lavrentyev Avenue 8/2, Novosibirsk 630090, Russia; Novosibirsk State University, Pirogova St. 2, Novosibirsk 630090, Russia
| | - Evgeniya N Andreyeva
- Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, Lavrentyev Avenue 8/2, Novosibirsk 630090, Russia
| | - Victor V Shloma
- Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, Lavrentyev Avenue 8/2, Novosibirsk 630090, Russia
| | - Igor F Zhimulev
- Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, Lavrentyev Avenue 8/2, Novosibirsk 630090, Russia; Novosibirsk State University, Pirogova St. 2, Novosibirsk 630090, Russia
| | - Terry L Orr-Weaver
- Whitehead Institute and Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142, USA.
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32
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Hua BL, Li S, Orr-Weaver TL. The role of transcription in the activation of a Drosophila amplification origin. G3 (BETHESDA, MD.) 2014; 4:2403-8. [PMID: 25320071 PMCID: PMC4267935 DOI: 10.1534/g3.114.014050] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Accepted: 10/11/2014] [Indexed: 12/30/2022]
Abstract
The mechanisms that underlie metazoan DNA replication initiation, especially the connection between transcription and replication origin activation, are not well understood. To probe the role of transcription in origin activation, we exploited a specific replication origin in Drosophila melanogaster follicle cells, ori62, which coincides with the yellow-g2 transcription unit and exhibits transcription-dependent origin firing. Within a 10-kb genomic fragment that contains ori62 and is sufficient for amplification, RNA-sequencing analysis revealed that all detected RNAs mapped solely to the yellow-g2 gene. To determine whether transcription is required in cis for ori62 firing, we generated a set of tagged yellow-g2 transgenes in which we could prevent local transcription across ori62 by deletions in the yellow-g2 promoter. Surprisingly, inhibition of yellow-g2 transcription by promoter deletions did not affect ori62 firing. Our results reveal that transcription in cis is not required for ori62 firing, raising the possibility that a trans-acting factor is required specifically for the activation of ori62. This finding illustrates that a diversity of mechanisms can be used in the regulation of metazoan DNA replication initiation.
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Affiliation(s)
- Brian L Hua
- Whitehead Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142 Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142
| | - Sharon Li
- Whitehead Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142
| | - Terry L Orr-Weaver
- Whitehead Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142 Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142
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33
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Hannibal RL, Chuong EB, Rivera-Mulia JC, Gilbert DM, Valouev A, Baker JC. Copy number variation is a fundamental aspect of the placental genome. PLoS Genet 2014; 10:e1004290. [PMID: 24785991 PMCID: PMC4006706 DOI: 10.1371/journal.pgen.1004290] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 02/20/2014] [Indexed: 11/19/2022] Open
Abstract
Discovery of lineage-specific somatic copy number variation (CNV) in mammals has led to debate over whether CNVs are mutations that propagate disease or whether they are a normal, and even essential, aspect of cell biology. We show that 1,000N polyploid trophoblast giant cells (TGCs) of the mouse placenta contain 47 regions, totaling 138 Megabases, where genomic copies are underrepresented (UR). UR domains originate from a subset of late-replicating heterochromatic regions containing gene deserts and genes involved in cell adhesion and neurogenesis. While lineage-specific CNVs have been identified in mammalian cells, classically in the immune system where V(D)J recombination occurs, we demonstrate that CNVs form during gestation in the placenta by an underreplication mechanism, not by recombination nor deletion. Our results reveal that large scale CNVs are a normal feature of the mammalian placental genome, which are regulated systematically during embryogenesis and are propagated by a mechanism of underreplication. Generally, every mammalian cell has the same complement of each part of its genome. However, copy number variation (CNV) can occur, where, compared to the rest of its genome, a cell has either more or less of a specific genomic region. It is unknown whether CNVs cause disease, or whether they are a normal aspect of cell biology. We investigated CNVs in polyploid trophoblast giant cells (TGCs) of the mouse placenta, which have up to 1,000 copies of the genome in each cell. We found that there are 47 regions with decreased copy number in TGCs, which we call underrepresented (UR) domains. These domains are marked in the TGC progenitor cells and we suggest that they gradually form during gestation due to slow replication versus fast replication of the rest of the genome. While UR domains contain cell adhesion and neuronal genes, they also contain significantly fewer genes than other genomic regions. Our results demonstrate that CNVs are a normal feature of the mammalian placental genome, which are regulated systematically during pregnancy.
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Affiliation(s)
- Roberta L. Hannibal
- Department of Genetics, Stanford University School of Medicine, Stanford, California, United States of America
| | - Edward B. Chuong
- Department of Genetics, Stanford University School of Medicine, Stanford, California, United States of America
| | - Juan Carlos Rivera-Mulia
- Department of Biological Science, Florida State University, Tallahassee, Tallahassee Florida, United States of America
| | - David M. Gilbert
- Department of Biological Science, Florida State University, Tallahassee, Tallahassee Florida, United States of America
| | - Anton Valouev
- Division of Bioinformatics, Department of Preventive Medicine, University of Southern California Keck School of Medicine, Los Angeles, California, United States of America
| | - Julie C. Baker
- Department of Genetics, Stanford University School of Medicine, Stanford, California, United States of America
- * E-mail:
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34
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Hassel C, Zhang B, Dixon M, Calvi BR. Induction of endocycles represses apoptosis independently of differentiation and predisposes cells to genome instability. Development 2013; 141:112-23. [PMID: 24284207 DOI: 10.1242/dev.098871] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The endocycle is a common developmental cell cycle variation wherein cells become polyploid through repeated genome duplication without mitosis. We previously showed that Drosophila endocycling cells repress the apoptotic cell death response to genotoxic stress. Here, we investigate whether it is differentiation or endocycle remodeling that promotes apoptotic repression. We find that when nurse and follicle cells switch into endocycles during oogenesis they repress the apoptotic response to DNA damage caused by ionizing radiation, and that this repression has been conserved in the genus Drosophila over 40 million years of evolution. Follicle cells defective for Notch signaling failed to switch into endocycles or differentiate and remained apoptotic competent. However, genetic ablation of mitosis by knockdown of Cyclin A or overexpression of fzr/Cdh1 induced follicle cell endocycles and repressed apoptosis independently of Notch signaling and differentiation. Cells recovering from these induced endocycles regained apoptotic competence, showing that repression is reversible. Recovery from fzr/Cdh1 overexpression also resulted in an error-prone mitosis with amplified centrosomes and high levels of chromosome loss and fragmentation. Our results reveal an unanticipated link between endocycles and the repression of apoptosis, with broader implications for how endocycles may contribute to genome instability and oncogenesis.
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Affiliation(s)
- Christiane Hassel
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
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35
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The ecdysone receptor (ScEcR-A) binds DNA puffs at the start of DNA amplification in Sciara coprophila. Chromosome Res 2013; 21:345-60. [PMID: 23737076 DOI: 10.1007/s10577-013-9360-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Revised: 04/11/2013] [Accepted: 04/23/2013] [Indexed: 12/20/2022]
Abstract
The steroid hormone ecdysone induces DNA amplification and subsequent DNA puff formation in late fourth larval instar salivary gland polytene chromosomes of the fungus fly, Sciara coprophila. Previous in vitro studies on DNA puff II/9A in Sciara demonstrated that the ecdysone receptor (ScEcR-A) efficiently binds an ecdysone response element adjacent to the origin recognition complex binding site within the II/9A amplification origin, implying a role for ScEcR-A in amplification. Here, we extrapolate the molecular details from locus II/9A to the rest of the genome using immunofluorescence with a ScEcR-A-specific antibody. ScEcR-A binds all DNA puff sites just as amplification begins and persists throughout the processes of amplification, transcription, and puffing. Ecdysone injections into pre-amplification stage larvae prematurely induce both DNA amplification and ScEcR-A binding to DNA puff sites. These data are consistent with a direct role for ScEcR-A in DNA amplification.
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36
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Sher N, Von Stetina JR, Bell GW, Matsuura S, Ravid K, Orr-Weaver TL. Fundamental differences in endoreplication in mammals and Drosophila revealed by analysis of endocycling and endomitotic cells. Proc Natl Acad Sci U S A 2013; 110:9368-73. [PMID: 23613587 PMCID: PMC3677442 DOI: 10.1073/pnas.1304889110] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Throughout the plant and animal kingdoms specific cell types become polyploid, increasing their DNA content to attain a large cell size. In mammals, megakaryocytes (MKs) become polyploid before fragmenting into platelets. The mammalian trophoblast giant cells (TGCs) exploit their size to form a barrier between the maternal and embryonic tissues. The mechanism of polyploidization has been investigated extensively in Drosophila, in which a modified cell cycle--the endocycle, consisting solely of alternating S and gap phases--produces polyploid tissues. During S phase in the Drosophila endocycle, heterochromatin and specific euchromatic regions are underreplicated and reduced in copy number. Here we investigate the properties of polyploidization in murine MKs and TGCs. We induced differentiation of primary MKs and directly microdissected TGCs from embryonic day 9.5 implantation sites. The copy number across the genome was analyzed by array-based comparative genome hybridization. In striking contrast to Drosophila, the genome was uniformly and integrally duplicated in both MKs and TGCs. This was true even for heterochromatic regions analyzed by quantitative PCR. Underreplication of specific regions in polyploid cells is proposed to be due to a slower S phase, resulting from low expression of S-phase genes, causing failure to duplicate late replicating genomic intervals. We defined the transcriptome of TGCs and found robust expression of S-phase genes. Similarly, S-phase gene expression is not repressed in MKs, providing an explanation for the distinct endoreplication parameters compared with Drosophila. Consistent with TGCs endocycling rather than undergoing endomitosis, they have low expression of M-phase genes.
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Affiliation(s)
| | | | | | - Shinobu Matsuura
- Departments of Medicine and Biochemistry, and Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA 02118
| | - Katya Ravid
- Departments of Medicine and Biochemistry, and Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA 02118
| | - Terry L. Orr-Weaver
- Whitehead Institute and
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142; and
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37
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Vorobyeva NE, Mazina MU, Golovnin AK, Kopytova DV, Gurskiy DY, Nabirochkina EN, Georgieva SG, Georgiev PG, Krasnov AN. Insulator protein Su(Hw) recruits SAGA and Brahma complexes and constitutes part of Origin Recognition Complex-binding sites in the Drosophila genome. Nucleic Acids Res 2013; 41:5717-30. [PMID: 23609538 PMCID: PMC3675495 DOI: 10.1093/nar/gkt297] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Despite increasing data on the properties of replication origins, molecular mechanisms underlying origin recognition complex (ORC) positioning in the genome are still poorly understood. The Su(Hw) protein accounts for the activity of best-studied Drosophila insulators. Here, we show that Su(Hw) recruits the histone acetyltransferase complex SAGA and chromatin remodeler Brahma to Su(Hw)-dependent insulators, which gives rise to regions with low nucleosome density and creates conditions for ORC binding. Depletion in Su(Hw) leads to a dramatic drop in the levels of SAGA, Brahma and ORC subunits and a significant increase in nucleosome density on Su(Hw)-dependent insulators, whereas artificial Su(Hw) recruitment itself is sufficient for subsequent SAGA, Brahma and ORC binding. In contrast to the majority of replication origins that associate with promoters of active genes, Su(Hw)-binding sites constitute a small proportion (6%) of ORC-binding sites that are localized preferentially in transcriptionally inactive chromatin regions termed BLACK and BLUE chromatin. We suggest that the key determinants of ORC positioning in the genome are DNA-binding proteins that constitute different DNA regulatory elements, including insulators, promoters and enhancers. Su(Hw) is the first example of such a protein.
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Affiliation(s)
- Nadezhda E Vorobyeva
- Department of Transcriptional Regulation and Chromatin Dynamics, Institute of Gene Biology, Russian Academy of Sciences, Moscow, 119334, Russia
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38
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Tang YC, Amon A. Gene copy-number alterations: a cost-benefit analysis. Cell 2013; 152:394-405. [PMID: 23374337 PMCID: PMC3641674 DOI: 10.1016/j.cell.2012.11.043] [Citation(s) in RCA: 250] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Revised: 10/22/2012] [Accepted: 11/01/2012] [Indexed: 11/25/2022]
Abstract
Changes in DNA copy number, whether confined to specific genes or affecting whole chromosomes, have been identified as causes of diseases and developmental abnormalities and as sources of adaptive potential. Here, we discuss the costs and benefits of DNA copy-number alterations. Changes in DNA copy number are largely detrimental. Amplifications or deletions of specific genes can elicit discrete defects. Large-scale changes in DNA copy number can also cause detrimental phenotypes that are due to the cumulative effects of copy-number alterations of many genes simultaneously. On the other hand, studies in microorganisms show that DNA copy-number alterations can be beneficial, increasing survival under selective pressure. As DNA copy-number alterations underlie many human diseases, we will end with a discussion of gene copy-number changes as therapeutic targets.
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Affiliation(s)
- Yun-Chi Tang
- David H. Koch Institute for Integrative Cancer Research, Howard Hughes Medical Institute, Massachusetts Institute of Technology, 76-561, 500 Main Street, Cambridge, MA 02139, USA
| | - Angelika Amon
- David H. Koch Institute for Integrative Cancer Research, Howard Hughes Medical Institute, Massachusetts Institute of Technology, 76-561, 500 Main Street, Cambridge, MA 02139, USA
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39
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Fox DT, Duronio RJ. Endoreplication and polyploidy: insights into development and disease. Development 2013; 140:3-12. [PMID: 23222436 DOI: 10.1242/dev.080531] [Citation(s) in RCA: 242] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Polyploid cells have genomes that contain multiples of the typical diploid chromosome number and are found in many different organisms. Studies in a variety of animal and plant developmental systems have revealed evolutionarily conserved mechanisms that control the generation of polyploidy and have recently begun to provide clues to its physiological function. These studies demonstrate that cellular polyploidy plays important roles during normal development and also contributes to human disease, particularly cancer.
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Affiliation(s)
- Donald T Fox
- Department of Pharmacology and Cancer Biology, and Department of Cell Biology, Duke University, Durham, NC 27710, USA.
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40
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McConnell KH, Dixon M, Calvi BR. The histone acetyltransferases CBP and Chameau integrate developmental and DNA replication programs in Drosophila ovarian follicle cells. Development 2012; 139:3880-90. [PMID: 22951641 DOI: 10.1242/dev.083576] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
DNA replication origin activity changes during development. Chromatin modifications are known to influence the genomic location of origins and the time during S phase that they initiate replication in different cells. However, how chromatin regulates origins in concert with cell differentiation remains poorly understood. Here, we use developmental gene amplification in Drosophila ovarian follicle cells as a model to investigate how chromatin modifiers regulate origins in a developmental context. We find that the histone acetyltransferase (HAT) Chameau (Chm) binds to amplicon origins and is partially required for their function. Depletion of Chm had relatively mild effects on origins during gene amplification and genomic replication compared with previous knockdown of its ortholog HBO1 in human cells, which has severe effects on origin function. We show that another HAT, CBP (Nejire), also binds amplicon origins and is partially required for amplification. Knockdown of Chm and CBP together had a more severe effect on nucleosome acetylation and amplicon origin activity than knockdown of either HAT alone, suggesting that these HATs collaborate in origin regulation. In addition to their local function at the origin, we show that Chm and CBP also globally regulate the developmental transition of follicle cells into the amplification stages of oogenesis. Our results reveal a complexity of origin epigenetic regulation by multiple HATs during development and suggest that chromatin modifiers are a nexus that integrates differentiation and DNA replication programs.
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41
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Abstract
As development unfolds, DNA replication is not only coordinated with cell proliferation, but is regulated uniquely in specific cell types and organs. This differential regulation of DNA synthesis requires crosstalk between DNA replication and differentiation. This dynamic aspect of DNA replication is highlighted by the finding that the distribution of replication origins varies between differentiated cell types and changes with differentiation. Moreover, differential DNA replication in some cell types can lead to increases or decreases in gene copy number along chromosomes. This review highlights the recent advances and technologies that have provided us with new insights into the developmental regulation of DNA replication.
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Affiliation(s)
- Jared Nordman
- Whitehead Institute and Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142, USA
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42
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Abstract
The origin recognition complex (ORC) was first discovered in the baker's yeast in 1992. Identification of ORC opened up a path for subsequent molecular level investigations on how eukaryotic cells initiate and control genome duplication each cell cycle. Twenty years after the first biochemical isolation, ORC is now taking on a three-dimensional shape, although a very blurry shape at the moment, thanks to the recent electron microscopy and image reconstruction efforts. In this chapter, we outline the current biochemical knowledge about ORC from several eukaryotic systems, with emphasis on the most recent structural and biochemical studies. Despite many species-specific properties, an emerging consensus is that ORC is an ATP-dependent machine that recruits other key proteins to form pre-replicative complexes (pre-RCs) at many origins of DNA replication, enabling the subsequent initiation of DNA replication in S phase.
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Affiliation(s)
- Huilin Li
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794, USA, And, Biology Department, Brookhaven National Laboratory, Upton, NY 11973, USA, , Tel: 631-344-2931, Fax: 631-344-3407
| | - Bruce Stillman
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA, , Tel: 516-367-8383
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43
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Sher N, Bell GW, Li S, Nordman J, Eng T, Eaton ML, Macalpine DM, Orr-Weaver TL. Developmental control of gene copy number by repression of replication initiation and fork progression. Genome Res 2011; 22:64-75. [PMID: 22090375 DOI: 10.1101/gr.126003.111] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Precise DNA replication is crucial for genome maintenance, yet this process has been inherently difficult to study on a genome-wide level in untransformed differentiated metazoan cells. To determine how metazoan DNA replication can be repressed, we examined regions selectively under-replicated in Drosophila polytene salivary glands, and found they are transcriptionally silent and enriched for the repressive H3K27me3 mark. In the first genome-wide analysis of binding of the origin recognition complex (ORC) in a differentiated metazoan tissue, we find that ORC binding is dramatically reduced within these large domains, suggesting reduced initiation as one mechanism leading to under-replication. Inhibition of replication fork progression by the chromatin protein SUUR is an additional repression mechanism to reduce copy number. Although repressive histone marks are removed when SUUR is mutated and copy number restored, neither transcription nor ORC binding is reinstated. Tethering of the SUUR protein to a specific site is insufficient to block replication, however. These results establish that developmental control of DNA replication, at both the initiation and elongation stages, is a mechanism to change gene copy number during differentiation.
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Affiliation(s)
- Noa Sher
- Whitehead Institute and Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA
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Liu J, McConnell K, Dixon M, Calvi BR. Analysis of model replication origins in Drosophila reveals new aspects of the chromatin landscape and its relationship to origin activity and the prereplicative complex. Mol Biol Cell 2011; 23:200-12. [PMID: 22049023 PMCID: PMC3248898 DOI: 10.1091/mbc.e11-05-0409] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
A study of model DNA replication origins in Drosophila reveals a codependence between histone acetylation and pre-RC assembly and leads to a chromatin switch model for the coordination of origin and promoter activity during development. Epigenetic regulation exerts a major influence on origins of DNA replication during development. The mechanisms for this regulation, however, are poorly defined. We showed previously that acetylation of nucleosomes regulates the origins that mediate developmental gene amplification during Drosophila oogenesis. Here we show that developmental activation of these origins is associated with acetylation of multiple histone lysines. Although these modifications are not unique to origin loci, we find that the level of acetylation is higher at the active origins and quantitatively correlated with the number of times these origins initiate replication. All of these acetylation marks were developmentally dynamic, rapidly increasing with origin activation and rapidly declining when the origins shut off and neighboring promoters turn on. Fine-scale analysis of the origins revealed that both hyperacetylation of nucleosomes and binding of the origin recognition complex (ORC) occur in a broad domain and that acetylation is highest on nucleosomes adjacent to one side of the major site of replication initiation. It was surprising to find that acetylation of some lysines depends on binding of ORC to the origin, suggesting that multiple histone acetyltransferases may be recruited during origin licensing. Our results reveal new insights into the origin epigenetic landscape and lead us to propose a chromatin switch model to explain the coordination of origin and promoter activity during development.
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Affiliation(s)
- Jun Liu
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
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Analysis of a Drosophila amplicon in follicle cells highlights the diversity of metazoan replication origins. Proc Natl Acad Sci U S A 2011; 108:16681-6. [PMID: 21933960 DOI: 10.1073/pnas.1114209108] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
To investigate the properties of metazoan replication origins, recent studies in cell culture have adopted the strategy of identifying origins using genome-wide approaches and assessing correlations with such features as transcription and histone modifications. Drosophila amplicon in follicle cells (DAFCs), genomic regions that undergo repeated rounds of DNA replication to increase DNA copy number, serve as powerful in vivo model replicons. Because there are six DAFCs, compared with thousands of origins activated in the typical S phase, close molecular characterization of all DAFCs is possible. To determine the extent to which the six DAFCs are different or similar, we investigated the developmental and replication properties of the newly identified DAFC-34B. DAFC-34B contains two genes expressed in follicle cells, although the timing and spatial patterns of expression suggest that amplification is not a strategy to promote high expression at this locus. Like the previously characterized DAFC-62D, DAFC-34B displays origin activation at two separate stages of development. However, unlike DAFC-62D, amplification at the later stage is not transcription-dependent. We mapped the DAFC-34B amplification origin to 1 kb by nascent strand analysis and delineated cis requirements for origin activation, finding that a 6-kb region, but not the 1-kb origin alone, is sufficient for amplification. We analyzed the developmental localization of the origin recognition complex (ORC) and the minichromosome maintenance (MCM)2-7 complex, the replicative helicase. Intriguingly, the final round of origin activation at DAFC-34B occurs in the absence of detectable ORC, although MCMs are present, suggesting a new amplification initiation mechanism.
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