1
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Impact of Chromosomal Context on Origin Selection and the Replication Program. Genes (Basel) 2022; 13:genes13071244. [PMID: 35886027 PMCID: PMC9318681 DOI: 10.3390/genes13071244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 06/28/2022] [Accepted: 07/08/2022] [Indexed: 02/01/2023] Open
Abstract
Eukaryotic DNA replication is regulated by conserved mechanisms that bring about a spatial and temporal organization in which distinct genomic domains are copied at characteristic times during S phase. Although this replication program has been closely linked with genome architecture, we still do not understand key aspects of how chromosomal context modulates the activity of replication origins. To address this question, we have exploited models that combine engineered genomic rearrangements with the unique replication programs of post-quiescence and pre-meiotic S phases. Our results demonstrate that large-scale inversions surprisingly do not affect cell proliferation and meiotic progression, despite inducing a restructuring of replication domains on each rearranged chromosome. Remarkably, these alterations in the organization of DNA replication are entirely due to changes in the positions of existing origins along the chromosome, as their efficiencies remain virtually unaffected genome wide. However, we identified striking alterations in origin firing proximal to the fusion points of each inversion, suggesting that the immediate chromosomal neighborhood of an origin is a crucial determinant of its activity. Interestingly, the impact of genome reorganization on replication initiation is highly comparable in the post-quiescent and pre-meiotic S phases, despite the differences in DNA metabolism in these two physiological states. Our findings therefore shed new light on how origin selection and the replication program are governed by chromosomal architecture.
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2
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Ben Yamin B, Ahmed-Seghir S, Tomida J, Despras E, Pouvelle C, Yurchenko A, Goulas J, Corre R, Delacour Q, Droin N, Dessen P, Goidin D, Lange SS, Bhetawal S, Mitjavila-Garcia MT, Baldacci G, Nikolaev S, Cadoret JC, Wood RD, Kannouche PL. DNA polymerase zeta contributes to heterochromatin replication to prevent genome instability. EMBO J 2021; 40:e104543. [PMID: 34533226 PMCID: PMC8561639 DOI: 10.15252/embj.2020104543] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 08/20/2021] [Accepted: 08/28/2021] [Indexed: 02/06/2023] Open
Abstract
The DNA polymerase zeta (Polζ) plays a critical role in bypassing DNA damage. REV3L, the catalytic subunit of Polζ, is also essential in mouse embryonic development and cell proliferation for reasons that remain incompletely understood. In this study, we reveal that REV3L protein interacts with heterochromatin components including repressive histone marks and localizes in pericentromeric regions through direct interaction with HP1 dimer. We demonstrate that Polζ/REV3L ensures progression of replication forks through difficult‐to‐replicate pericentromeric heterochromatin, thereby preventing spontaneous chromosome break formation. We also find that Rev3l‐deficient cells are compromised in the repair of heterochromatin‐associated double‐stranded breaks, eliciting deletions in late‐replicating regions. Lack of REV3L leads to further consequences that may be ascribed to heterochromatin replication and repair‐associated functions of Polζ, with a disruption of the temporal replication program at specific loci. This is correlated with changes in epigenetic landscape and transcriptional control of developmentally regulated genes. These results reveal a new function of Polζ in preventing chromosome instability during replication of heterochromatic regions.
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Affiliation(s)
- Barbara Ben Yamin
- CNRS-UMR9019, Equipe labellisée Ligue Contre le Cancer, Gustave Roussy, Paris-Saclay Université, Villejuif, France
| | - Sana Ahmed-Seghir
- CNRS-UMR9019, Equipe labellisée Ligue Contre le Cancer, Gustave Roussy, Paris-Saclay Université, Villejuif, France
| | - Junya Tomida
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center and The University of Texas MD Anderson Cancer Center UT Health Graduate School of Biomedical Sciences, Houston, TX, USA
| | - Emmanuelle Despras
- CNRS-UMR9019, Equipe labellisée Ligue Contre le Cancer, Gustave Roussy, Paris-Saclay Université, Villejuif, France
| | - Caroline Pouvelle
- CNRS-UMR9019, Equipe labellisée Ligue Contre le Cancer, Gustave Roussy, Paris-Saclay Université, Villejuif, France
| | - Andrey Yurchenko
- INSERM U981, Gustave Roussy, Université Paris Saclay, Villejuif, France
| | - Jordane Goulas
- CNRS-UMR9019, Equipe labellisée Ligue Contre le Cancer, Gustave Roussy, Paris-Saclay Université, Villejuif, France
| | - Raphael Corre
- CNRS-UMR9019, Equipe labellisée Ligue Contre le Cancer, Gustave Roussy, Paris-Saclay Université, Villejuif, France
| | - Quentin Delacour
- CNRS-UMR9019, Equipe labellisée Ligue Contre le Cancer, Gustave Roussy, Paris-Saclay Université, Villejuif, France
| | | | - Philippe Dessen
- Bioinformatics Core Facility, Gustave Roussy, Villejuif, France
| | - Didier Goidin
- Life Sciences and Diagnostics Group, Agilent Technologies France, Les Ulis, France
| | - Sabine S Lange
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center and The University of Texas MD Anderson Cancer Center UT Health Graduate School of Biomedical Sciences, Houston, TX, USA
| | - Sarita Bhetawal
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center and The University of Texas MD Anderson Cancer Center UT Health Graduate School of Biomedical Sciences, Houston, TX, USA
| | | | - Giuseppe Baldacci
- Institut Jacques Monod, UMR7592, CNRS and University of Paris, Paris, France
| | - Sergey Nikolaev
- INSERM U981, Gustave Roussy, Université Paris Saclay, Villejuif, France
| | | | - Richard D Wood
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center and The University of Texas MD Anderson Cancer Center UT Health Graduate School of Biomedical Sciences, Houston, TX, USA
| | - Patricia L Kannouche
- CNRS-UMR9019, Equipe labellisée Ligue Contre le Cancer, Gustave Roussy, Paris-Saclay Université, Villejuif, France
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3
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Kirstein N, Buschle A, Wu X, Krebs S, Blum H, Kremmer E, Vorberg IM, Hammerschmidt W, Lacroix L, Hyrien O, Audit B, Schepers A. Human ORC/MCM density is low in active genes and correlates with replication time but does not delimit initiation zones. eLife 2021; 10:62161. [PMID: 33683199 PMCID: PMC7993996 DOI: 10.7554/elife.62161] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Accepted: 03/05/2021] [Indexed: 12/22/2022] Open
Abstract
Eukaryotic DNA replication initiates during S phase from origins that have been licensed in the preceding G1 phase. Here, we compare ChIP-seq profiles of the licensing factors Orc2, Orc3, Mcm3, and Mcm7 with gene expression, replication timing, and fork directionality profiles obtained by RNA-seq, Repli-seq, and OK-seq. Both, the origin recognition complex (ORC) and the minichromosome maintenance complex (MCM) are significantly and homogeneously depleted from transcribed genes, enriched at gene promoters, and more abundant in early- than in late-replicating domains. Surprisingly, after controlling these variables, no difference in ORC/MCM density is detected between initiation zones, termination zones, unidirectionally replicating regions, and randomly replicating regions. Therefore, ORC/MCM density correlates with replication timing but does not solely regulate the probability of replication initiation. Interestingly, H4K20me3, a histone modification proposed to facilitate late origin licensing, was enriched in late-replicating initiation zones and gene deserts of stochastic replication fork direction. We discuss potential mechanisms specifying when and where replication initiates in human cells.
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Affiliation(s)
- Nina Kirstein
- Research Unit Gene Vectors, Helmholtz Zentrum München (GmbH), German Research Center for Environmental Health, Munich, Germany
| | - Alexander Buschle
- Research Unit Gene Vectors, Helmholtz Zentrum München (GmbH), German Research Center for Environmental Health and German Center for Infection Research (DZIF), Munich, Germany
| | - Xia Wu
- Institut de Biologie de l'ENS (IBENS), Département de Biologie, Ecole Normale Supérieure, CNRS, Inserm, PSL Research University, Paris, France
| | - Stefan Krebs
- Laboratory for Functional Genome Analysis (LAFUGA), Gene Center of the Ludwig-Maximilians Universität (LMU) München, Munich, Germany
| | - Helmut Blum
- Laboratory for Functional Genome Analysis (LAFUGA), Gene Center of the Ludwig-Maximilians Universität (LMU) München, Munich, Germany
| | - Elisabeth Kremmer
- Institute for Molecular Immunology, Monoclonal Antibody Core Facility, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Neuherberg, Germany
| | - Ina M Vorberg
- German Center for Neurodegenerative Diseases (DZNE e.V.), Bonn, Germany.,Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
| | - Wolfgang Hammerschmidt
- Research Unit Gene Vectors, Helmholtz Zentrum München (GmbH), German Research Center for Environmental Health and German Center for Infection Research (DZIF), Munich, Germany
| | - Laurent Lacroix
- Institut de Biologie de l'ENS (IBENS), Département de Biologie, Ecole Normale Supérieure, CNRS, Inserm, PSL Research University, Paris, France
| | - Olivier Hyrien
- Institut de Biologie de l'ENS (IBENS), Département de Biologie, Ecole Normale Supérieure, CNRS, Inserm, PSL Research University, Paris, France
| | - Benjamin Audit
- Univ Lyon, ENS de Lyon, Univ. Claude Bernard, CNRS, Laboratoire de Physique, 69342 Lyon, France
| | - Aloys Schepers
- Research Unit Gene Vectors, Helmholtz Zentrum München (GmbH), German Research Center for Environmental Health, Munich, Germany
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4
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In Vivo Analysis of mtDNA Replication at the Single Molecule Level and with High Resolution. Methods Mol Biol 2020. [PMID: 33230762 DOI: 10.1007/978-1-0716-0834-0_2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Single molecule analysis of replicating DNA (SMARD) is a powerful methodology that allows in vivo analysis of replicating DNA; identification of origins of replication, assessment of fork directionality, and measurement of replication fork speed. SMARD, which has been extensively used to study replication of nuclear DNA, involves incorporation of thymidine analogs to nascent DNA chains and their subsequent visualization through immune detection. Here, we adapt and fine-tune the SMARD technique to the specifics of human and mouse mitochondrial DNA. The mito-SMARD protocol allows researchers to gain in vivo insight into mitochondrial DNA (mtDNA) replication at the single molecule level and with high resolution.
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5
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Miura H, Takahashi S, Shibata T, Nagao K, Obuse C, Okumura K, Ogata M, Hiratani I, Takebayashi SI. Mapping replication timing domains genome wide in single mammalian cells with single-cell DNA replication sequencing. Nat Protoc 2020; 15:4058-4100. [PMID: 33230331 DOI: 10.1038/s41596-020-0378-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Accepted: 07/02/2020] [Indexed: 01/03/2023]
Abstract
Replication timing (RT) domains are stable units of chromosome structure that are regulated in the context of development and disease. Conventional genome-wide RT mapping methods require many S-phase cells for either the effective enrichment of replicating DNA through bromodeoxyuridine (BrdU) immunoprecipitation or the determination of copy-number differences during S-phase, which precludes their application to non-abundant cell types and single cells. Here, we provide a simple, cost-effective, and robust protocol for single-cell DNA replication sequencing (scRepli-seq). The scRepli-seq methodology relies on whole-genome amplification (WGA) of genomic DNA (gDNA) from single S-phase cells and next-generation sequencing (NGS)-based determination of copy-number differences that arise between replicated and unreplicated DNA. Haplotype-resolved scRepli-seq, which distinguishes pairs of homologous chromosomes within a single cell, is feasible by using single-nucleotide polymorphism (SNP)/indel information. We also provide computational pipelines for quality control, normalization, and binarization of the scRepli-seq data. The experimental portion of this protocol (before sequencing) takes 3 d.
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Affiliation(s)
- Hisashi Miura
- Laboratory for Developmental Epigenetics, RIKEN Center for Biosystems Dynamics Research (BDR), Kobe, Japan
| | - Saori Takahashi
- Laboratory for Developmental Epigenetics, RIKEN Center for Biosystems Dynamics Research (BDR), Kobe, Japan
| | - Takahiro Shibata
- Department of Biochemistry and Proteomics, Graduate School of Medicine, Mie University, Tsu, Japan.,Laboratory of Molecular & Cellular Biology, Graduate School of Bioresources, Mie University, Tsu, Japan
| | - Koji Nagao
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Japan
| | - Chikashi Obuse
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Japan
| | - Katsuzumi Okumura
- Laboratory of Molecular & Cellular Biology, Graduate School of Bioresources, Mie University, Tsu, Japan
| | - Masato Ogata
- Department of Biochemistry and Proteomics, Graduate School of Medicine, Mie University, Tsu, Japan
| | - Ichiro Hiratani
- Laboratory for Developmental Epigenetics, RIKEN Center for Biosystems Dynamics Research (BDR), Kobe, Japan.
| | - Shin-Ichiro Takebayashi
- Department of Biochemistry and Proteomics, Graduate School of Medicine, Mie University, Tsu, Japan. .,Laboratory of Molecular & Cellular Biology, Graduate School of Bioresources, Mie University, Tsu, Japan.
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6
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Falbo L, Costanzo V. Epigenetic regulation of replication origin assembly: A role for histone H1 and chromatin remodeling factors. Bioessays 2020; 43:e2000181. [PMID: 33165968 DOI: 10.1002/bies.202000181] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 09/09/2020] [Accepted: 09/18/2020] [Indexed: 12/18/2022]
Abstract
During early embryonic development in several metazoans, accurate DNA replication is ensured by high number of replication origins. This guarantees rapid genome duplication coordinated with fast cell divisions. In Xenopus laevis embryos this program switches to one with a lower number of origins at a developmental stage known as mid-blastula transition (MBT) when cell cycle length increases and gene transcription starts. Consistent with this regulation, somatic nuclei replicate poorly when transferred to eggs, suggesting the existence of an epigenetic memory suppressing replication assembly origins at all available sites. Recently, it was shown that histone H1 imposes a non-permissive chromatin configuration preventing replication origin assembly on somatic nuclei. This somatic state can be erased by SSRP1, a subunit of the FACT complex. Here, we further develop the hypothesis that this novel form of epigenetic memory might impact on different areas of vertebrate biology going from nuclear reprogramming to cancer development.
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Affiliation(s)
- Lucia Falbo
- IFOM, The FIRC Institute of Molecular Oncology, Via Adamello 16, Milan, 20139, Italy
| | - Vincenzo Costanzo
- IFOM, The FIRC Institute of Molecular Oncology, Via Adamello 16, Milan, 20139, Italy.,Department of Oncology and Haematology-Oncology, University of Milan, Milan, Italy
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7
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Georgieva D, Liu Q, Wang K, Egli D. Detection of base analogs incorporated during DNA replication by nanopore sequencing. Nucleic Acids Res 2020; 48:e88. [PMID: 32710620 PMCID: PMC7470954 DOI: 10.1093/nar/gkaa517] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Revised: 05/28/2020] [Accepted: 06/05/2020] [Indexed: 01/23/2023] Open
Abstract
DNA synthesis is a fundamental requirement for cell proliferation and DNA repair, but no single method can identify the location, direction and speed of replication forks with high resolution. Mammalian cells have the ability to incorporate thymidine analogs along with the natural A, T, G and C bases during DNA synthesis, which allows for labeling of replicating or repaired DNA. Here, we demonstrate the use of the Oxford Nanopore Technologies MinION to detect 11 different thymidine analogs including CldU, BrdU, IdU as well as EdU alone or coupled to Biotin and other bulky adducts in synthetic DNA templates. We also show that the large adduct Biotin can be distinguished from the smaller analog IdU, which opens the possibility of using analog combinations to identify the location and direction of DNA synthesis. Furthermore, we detect IdU label on single DNA molecules in the genome of mouse pluripotent stem cells and using CRISPR/Cas9-mediated enrichment, determine replication rates using newly synthesized DNA strands in human mitochondrial DNA. We conclude that this novel method, termed Replipore sequencing, has the potential for on target examination of DNA replication in a wide range of biological contexts.
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Affiliation(s)
- Daniela Georgieva
- Integrated Program in Cellular, Molecular, and Biomedical Studies, Columbia University, New York, NY 10032, USA.,Naomi Berrie Diabetes Center, Columbia University, New York NY 10032, USA.,Columbia Stem Cell Initiative, Columbia University, New York, NY 10032, USA
| | - Qian Liu
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Kai Wang
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA.,Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Dieter Egli
- Naomi Berrie Diabetes Center, Columbia University, New York NY 10032, USA.,Columbia Stem Cell Initiative, Columbia University, New York, NY 10032, USA.,Department of Pediatrics and Department of Obstetrics and Gynecology, Columbia University, New York, NY 10032, USA
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8
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Joseph SA, Taglialatela A, Leuzzi G, Huang JW, Cuella-Martin R, Ciccia A. Time for remodeling: SNF2-family DNA translocases in replication fork metabolism and human disease. DNA Repair (Amst) 2020; 95:102943. [PMID: 32971328 DOI: 10.1016/j.dnarep.2020.102943] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Revised: 07/24/2020] [Accepted: 07/26/2020] [Indexed: 02/07/2023]
Abstract
Over the course of DNA replication, DNA lesions, transcriptional intermediates and protein-DNA complexes can impair the progression of replication forks, thus resulting in replication stress. Failure to maintain replication fork integrity in response to replication stress leads to genomic instability and predisposes to the development of cancer and other genetic disorders. Multiple DNA damage and repair pathways have evolved to allow completion of DNA replication following replication stress, thus preserving genomic integrity. One of the processes commonly induced in response to replication stress is fork reversal, which consists in the remodeling of stalled replication forks into four-way DNA junctions. In normal conditions, fork reversal slows down replication fork progression to ensure accurate repair of DNA lesions and facilitates replication fork restart once the DNA lesions have been removed. However, in certain pathological situations, such as the deficiency of DNA repair factors that protect regressed forks from nuclease-mediated degradation, fork reversal can cause genomic instability. In this review, we describe the complex molecular mechanisms regulating fork reversal, with a focus on the role of the SNF2-family fork remodelers SMARCAL1, ZRANB3 and HLTF, and highlight the implications of fork reversal for tumorigenesis and cancer therapy.
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Affiliation(s)
- Sarah A Joseph
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Angelo Taglialatela
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Giuseppe Leuzzi
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Jen-Wei Huang
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Raquel Cuella-Martin
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Alberto Ciccia
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA.
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9
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Hulke ML, Massey DJ, Koren A. Genomic methods for measuring DNA replication dynamics. Chromosome Res 2020; 28:49-67. [PMID: 31848781 PMCID: PMC7131883 DOI: 10.1007/s10577-019-09624-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 11/30/2019] [Accepted: 12/03/2019] [Indexed: 12/27/2022]
Abstract
Genomic DNA replicates according to a defined temporal program in which early-replicating loci are associated with open chromatin, higher gene density, and increased gene expression levels, while late-replicating loci tend to be heterochromatic and show higher rates of genomic instability. The ability to measure DNA replication dynamics at genome scale has proven crucial for understanding the mechanisms and cellular consequences of DNA replication timing. Several methods, such as quantification of nucleotide analog incorporation and DNA copy number analyses, can accurately reconstruct the genomic replication timing profiles of various species and cell types. More recent developments have expanded the DNA replication genomic toolkit to assays that directly measure the activity of replication origins, while single-cell replication timing assays are beginning to reveal a new level of replication timing regulation. The combination of these methods, applied on a genomic scale and in multiple biological systems, promises to resolve many open questions and lead to a holistic understanding of how eukaryotic cells replicate their genomes accurately and efficiently.
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Affiliation(s)
- Michelle L Hulke
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, 14853, USA
| | - Dashiell J Massey
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, 14853, USA
| | - Amnon Koren
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, 14853, USA.
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10
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Yehuda Y, Blumenfeld B, Mayorek N, Makedonski K, Vardi O, Cohen-Daniel L, Mansour Y, Baror-Sebban S, Masika H, Farago M, Berger M, Carmi S, Buganim Y, Koren A, Simon I. Germline DNA replication timing shapes mammalian genome composition. Nucleic Acids Res 2019; 46:8299-8310. [PMID: 29986092 PMCID: PMC6144785 DOI: 10.1093/nar/gky610] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2018] [Accepted: 06/26/2018] [Indexed: 12/13/2022] Open
Abstract
Mammalian DNA replication is a highly organized and regulated process. Large, Mb-sized regions are replicated at defined times along S-phase. Replication Timing (RT) is thought to play a role in shaping the mammalian genome by affecting mutation rates. Previous analyses relied on somatic RT profiles. However, only germline mutations are passed on to offspring and affect genomic composition. Therefore, germ cell RT information is necessary to evaluate the influences of RT on the mammalian genome. We adapted the RT mapping technique for limited amounts of cells, and measured RT from two stages in the mouse germline - primordial germ cells (PGCs) and spermatogonial stem cells (SSCs). RT in germline cells exhibited stronger correlations to both mutation rate and recombination hotspots density than those of RT in somatic tissues, emphasizing the importance of using correct tissues-of-origin for RT profiling. Germline RT maps exhibited stronger correlations to additional genetic features including GC-content, transposable elements (SINEs and LINEs), and gene density. GC content stratification and multiple regression analysis revealed independent contributions of RT to SINE, gene, mutation, and recombination hotspot densities. Together, our results establish a central role for RT in shaping multiple levels of mammalian genome composition.
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Affiliation(s)
- Yishai Yehuda
- Department of Microbiology and Molecular Genetics, IMRIC, Hebrew University-Hadassah Medical School, Jerusalem, Israel.,Department of Bioinformatics, Jerusalem College of Technology, Jerusalem, Israel
| | - Britny Blumenfeld
- Department of Microbiology and Molecular Genetics, IMRIC, Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Nina Mayorek
- The Concern Foundation Laboratories at The Lautenberg Center for Immunology and Cancer Research, IMRIC, Faculty of Medicine, The Hebrew University, Jerusalem, Israel
| | - Kirill Makedonski
- Department of Developmental Biology and Cancer Research, IMRIC, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Oriya Vardi
- Department of Microbiology and Molecular Genetics, IMRIC, Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Leonor Cohen-Daniel
- The Concern Foundation Laboratories at The Lautenberg Center for Immunology and Cancer Research, IMRIC, Faculty of Medicine, The Hebrew University, Jerusalem, Israel
| | - Yousef Mansour
- The Concern Foundation Laboratories at The Lautenberg Center for Immunology and Cancer Research, IMRIC, Faculty of Medicine, The Hebrew University, Jerusalem, Israel
| | - Shulamit Baror-Sebban
- Department of Developmental Biology and Cancer Research, IMRIC, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Hagit Masika
- Department of Developmental Biology and Cancer Research, IMRIC, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Marganit Farago
- Department of Developmental Biology and Cancer Research, IMRIC, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Michael Berger
- The Concern Foundation Laboratories at The Lautenberg Center for Immunology and Cancer Research, IMRIC, Faculty of Medicine, The Hebrew University, Jerusalem, Israel
| | - Shai Carmi
- Braun School of Public Health and Community Medicine, the Hebrew University of Jerusalem, Jerusalem, Israel
| | - Yosef Buganim
- Department of Developmental Biology and Cancer Research, IMRIC, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Amnon Koren
- Deptartment of Molecular Biology and Genetics, Cornell University, Ithaca, NY, USA
| | - Itamar Simon
- Department of Microbiology and Molecular Genetics, IMRIC, Hebrew University-Hadassah Medical School, Jerusalem, Israel
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11
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Kolesnikova TD, Antonenko OV, Makunin IV. Replication timing in Drosophila and its peculiarities in polytene chromosomes. Vavilovskii Zhurnal Genet Selektsii 2019. [DOI: 10.18699/vj19.473] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Drosophila melanogaster is one of the popular model organisms in DNA replication studies. Since the 1960s, DNA replication of polytene chromosomes has been extensively studied by cytological methods. In the recent two decades, the progress in our understanding of DNA replication was associated with new techniques. Use of fluorescent dyes increased the resolution of cytological methods significantly. High-throughput methods allowed analysis of DNA replication on a genome scale, as well as its correlation with chromatin structure and gene activi ty. Precise mapping of the cytological structures of polytene chromosomes to the genome assembly allowed comparison of replication between polytene chromosomes and chromosomes of diploid cells. New features of replication characteristic for D. melanogaster were described for both diploid and polytene chromosomes. Comparison of genomic replication profiles revealed a significant similarity between Drosophila and other well-studi ed eukaryotic species, such as human. Early replication is often confined to intensely transcribed gene-dense regions characterized by multiple replication initiation sites. Features of DNA replication in Drosophila might be explained by a compact genome. The organization of replication in polytene chromosomes has much in common with the organization of replication in chromosomes in diploid cells. The most important feature of replication in polytene chromosomes is its low rate and the dependence of S-phase duration on many factors: external and internal, local and global. The speed of replication forks in D. melanogaster polytene chromosomes is affected by SUUR and Rif1 proteins. It is not known yet how universal the mechanisms associated with these factors are, but their study is very promising.
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Affiliation(s)
- T. D. Kolesnikova
- Institute of Molecular and Cellular Biology, SB RAS. Novosibirsk State University
| | | | - I. V. Makunin
- Institute of Molecular and Cellular Biology, SB RAS; Research Computing Centre, The University of Queensland
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12
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Hiratani I, Takahashi S. DNA Replication Timing Enters the Single-Cell Era. Genes (Basel) 2019; 10:genes10030221. [PMID: 30884743 PMCID: PMC6470765 DOI: 10.3390/genes10030221] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Revised: 03/12/2019] [Accepted: 03/12/2019] [Indexed: 12/20/2022] Open
Abstract
In mammalian cells, DNA replication timing is controlled at the level of megabase (Mb)-sized chromosomal domains and correlates well with transcription, chromatin structure, and three-dimensional (3D) genome organization. Because of these properties, DNA replication timing is an excellent entry point to explore genome regulation at various levels and a variety of studies have been carried out over the years. However, DNA replication timing studies traditionally required at least tens of thousands of cells, and it was unclear whether the replication domains detected by cell population analyses were preserved at the single-cell level. Recently, single-cell DNA replication profiling methods became available, which revealed that the Mb-sized replication domains detected by cell population analyses were actually well preserved in individual cells. In this article, we provide a brief overview of our current knowledge on DNA replication timing regulation in mammals based on cell population studies, outline the findings from single-cell DNA replication profiling, and discuss future directions and challenges.
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Affiliation(s)
- Ichiro Hiratani
- Laboratory for Developmental Epigenetics, RIKEN Center for Biosystems Dynamics Research (BDR), Kobe, Hyogo 650-0047, Japan.
| | - Saori Takahashi
- Laboratory for Developmental Epigenetics, RIKEN Center for Biosystems Dynamics Research (BDR), Kobe, Hyogo 650-0047, Japan.
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Pilzecker B, Jacobs H. Mutating for Good: DNA Damage Responses During Somatic Hypermutation. Front Immunol 2019; 10:438. [PMID: 30915081 PMCID: PMC6423074 DOI: 10.3389/fimmu.2019.00438] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Accepted: 02/19/2019] [Indexed: 11/13/2022] Open
Abstract
Somatic hypermutation (SHM) of immunoglobulin (Ig) genes plays a key role in antibody mediated immunity. SHM in B cells provides the molecular basis for affinity maturation of antibodies. In this way SHM is key in optimizing antibody dependent immune responses. SHM is initiated by targeting the Activation-Induced Cytidine Deaminase (AID) to rearranged V(D)J and switch regions of Ig genes. The mutation rate of this programmed mutagenesis is ~10-3 base pairs per generation, a million-fold higher than the non-AID targeted genome of B cells. AID is a processive enzyme that binds single-stranded DNA and deaminates cytosines in DNA. Cytosine deamination generates highly mutagenic deoxy-uracil (U) in the DNA of both strands of the Ig loci. Mutagenic processing of the U by the DNA damage response generates the entire spectrum of base substitutions characterizing SHM at and around the initial U lesion. Starting from the U as a primary lesion, currently five mutagenic DNA damage response pathways have been identified in generating a well-defined SHM spectrum of C/G transitions, C/G transversions, and A/T mutations around this initial lesion. These pathways include (1) replication opposite template U generates transitions at C/G, (2) UNG2-dependent translesion synthesis (TLS) generates transversions at C/G, (3) a hybrid pathway comprising non-canonical mismatch repair (ncMMR) and UNG2-dependent TLS generates transversions at C/G, (4) ncMMR generates mutations at A/T, and (5) UNG2- and PCNA Ubiquitination (PCNA-Ub)-dependent mutations at A/T. Furthermore, specific strand-biases of SHM spectra arise as a consequence of a biased AID targeting, ncMMR, and anti-mutagenic repriming. Here, we review mammalian SHM with special focus on the mutagenic DNA damage response pathways involved in processing AID induced Us, the origin of characteristic strand biases, and relevance of the cell cycle.
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Affiliation(s)
| | - Heinz Jacobs
- Division of Tumor Biology & Immunology, The Netherlands Cancer Institute, Amsterdam, Netherlands
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14
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Genome-wide stability of the DNA replication program in single mammalian cells. Nat Genet 2019; 51:529-540. [PMID: 30804559 DOI: 10.1038/s41588-019-0347-5] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2017] [Accepted: 01/09/2019] [Indexed: 11/09/2022]
Abstract
Here, we report a single-cell DNA replication sequencing method, scRepli-seq, a genome-wide methodology that measures copy number differences between replicated and unreplicated DNA. Using scRepli-seq, we demonstrate that replication-domain organization is conserved among individual mouse embryonic stem cells (mESCs). Differentiated mESCs exhibited distinct profiles, which were also conserved among cells. Haplotype-resolved scRepli-seq revealed similar replication profiles of homologous autosomes, while the inactive X chromosome was clearly replicated later than its active counterpart. However, a small degree of cell-to-cell replication-timing heterogeneity was present, which was smallest at the beginning and the end of S phase. In addition, developmentally regulated domains were found to deviate from others and showed a higher degree of heterogeneity, thus suggesting a link to developmental plasticity. Moreover, allelic expression imbalance was found to strongly associate with replication-timing asynchrony. Our results form a foundation for single-cell-level understanding of DNA replication regulation and provide insights into three-dimensional genome organization.
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15
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Munden A, Rong Z, Sun A, Gangula R, Mallal S, Nordman JT. Rif1 inhibits replication fork progression and controls DNA copy number in Drosophila. eLife 2018; 7:e39140. [PMID: 30277458 PMCID: PMC6185109 DOI: 10.7554/elife.39140] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 10/01/2018] [Indexed: 12/22/2022] Open
Abstract
Control of DNA copy number is essential to maintain genome stability and ensure proper cell and tissue function. In Drosophila polyploid cells, the SNF2-domain-containing SUUR protein inhibits replication fork progression within specific regions of the genome to promote DNA underreplication. While dissecting the function of SUUR's SNF2 domain, we identified an interaction between SUUR and Rif1. Rif1 has many roles in DNA metabolism and regulates the replication timing program. We demonstrate that repression of DNA replication is dependent on Rif1. Rif1 localizes to active replication forks in a partially SUUR-dependent manner and directly regulates replication fork progression. Importantly, SUUR associates with replication forks in the absence of Rif1, indicating that Rif1 acts downstream of SUUR to inhibit fork progression. Our findings uncover an unrecognized function of the Rif1 protein as a regulator of replication fork progression.
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Affiliation(s)
- Alexander Munden
- Department of Biological SciencesVanderbilt UniversityNashvilleUnited States
| | - Zhan Rong
- Department of Biological SciencesVanderbilt UniversityNashvilleUnited States
| | - Amanda Sun
- Department of Biological SciencesVanderbilt UniversityNashvilleUnited States
| | - Rama Gangula
- Department of MedicineVanderbilt University School of MedicineNashvilleUnited States
| | - Simon Mallal
- Department of MedicineVanderbilt University School of MedicineNashvilleUnited States
- Department of Pathology, Microbiology and ImmunologyVanderbilt University School of MedicineNashvilleUnited States
| | - Jared T Nordman
- Department of Biological SciencesVanderbilt UniversityNashvilleUnited States
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16
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Aze A, Maiorano D. Recent advances in understanding DNA replication: cell type-specific adaptation of the DNA replication program. F1000Res 2018; 7. [PMID: 30228862 PMCID: PMC6117848 DOI: 10.12688/f1000research.15408.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 08/20/2018] [Indexed: 12/11/2022] Open
Abstract
DNA replication is an essential process occurring prior to cell division. Cell division coupled to proliferation ensures the growth and renewal of a large variety of specialized cell types generated during embryonic development. Changes in the DNA replication program occur during development. Embryonic undifferentiated cells show a high replication rate and fast proliferation, whereas more differentiated cells are characterized by reduced DNA synthesis and a low proliferation rate. Hence, the DNA replication program must adapt to the specific features of cells committed to different fates. Recent findings on DNA synthesis regulation in different cell types open new perspectives for developing efficient and more adapted therapies to treat various diseases such as genetic diseases and cancer. This review will put the emphasis on recent progress made in this field.
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Affiliation(s)
- Antoine Aze
- Institute of Human Genetics, UMR9002, CNRS-University of Montpellier, Montpellier, 34396 Cedex 5, France
| | - Domenico Maiorano
- Institute of Human Genetics, UMR9002, CNRS-University of Montpellier, Montpellier, 34396 Cedex 5, France
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17
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Fu H, Baris A, Aladjem MI. Replication timing and nuclear structure. Curr Opin Cell Biol 2018; 52:43-50. [PMID: 29414592 PMCID: PMC5988923 DOI: 10.1016/j.ceb.2018.01.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Revised: 01/05/2018] [Accepted: 01/14/2018] [Indexed: 12/12/2022]
Abstract
DNA replication proceeds along spatially and temporally coordinated patterns within the nucleus, thus protecting the genome during the synthesis of new genetic material. While we have been able to visualize replication patterns on DNA fibers for 50 years, recent developments and discoveries have provided a greater insight into how DNA replication is controlled. In this review, we highlight many of these discoveries. Of great interest are the physiological role of the replication timing program, cis and trans-acting factors that modulate replication timing and the effects of chromatin structure on the replication timing program. We also discuss future directions in the study of replication timing.
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Affiliation(s)
- Haiqing Fu
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, 37 Convent Drive, Bethesda, MD 20892, United States
| | - Adrian Baris
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, 37 Convent Drive, Bethesda, MD 20892, United States
| | - Mirit I Aladjem
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, 37 Convent Drive, Bethesda, MD 20892, United States.
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18
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Zhao PA, Rivera-Mulia JC, Gilbert DM. Replication Domains: Genome Compartmentalization into Functional Replication Units. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1042:229-257. [DOI: 10.1007/978-981-10-6955-0_11] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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19
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DNA Replication Origins in Immunoglobulin Switch Regions Regulate Class Switch Recombination in an R-Loop-Dependent Manner. Cell Rep 2017; 17:2927-2942. [PMID: 27974207 DOI: 10.1016/j.celrep.2016.11.041] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Revised: 09/07/2016] [Accepted: 11/11/2016] [Indexed: 11/22/2022] Open
Abstract
Class switch recombination (CSR) at the immunoglobulin heavy chain (IgH) locus generates antibody isotypes. CSR depends on double-strand breaks (DSBs) induced by activation-induced cytidine deaminase (AID). Although DSB formation and repair machineries are active in G1 phase, efficient CSR is dependent on cell proliferation and S phase entry; however, the underlying mechanisms are obscure. Here, we show that efficient CSR requires the replicative helicase, the Mcm complex. Mcm proteins are enriched at IgH switch regions during CSR, leading to assembly of facultative replication origins that require Mcm helicase function for productive CSR. Assembly of CSR-associated origins is facilitated by R loops and promotes the physical proximity (synapsis) of recombining switch regions, which is reduced by R loop inhibition or Mcm complex depletion. Thus, R loops contribute to replication origin specification that promotes DSB resolution in CSR. This suggests a mechanism for the dependence of CSR on S phase and cell division.
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20
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Anatomy of Mammalian Replication Domains. Genes (Basel) 2017; 8:genes8040110. [PMID: 28350365 PMCID: PMC5406857 DOI: 10.3390/genes8040110] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Revised: 03/22/2017] [Accepted: 03/24/2017] [Indexed: 02/07/2023] Open
Abstract
Genetic information is faithfully copied by DNA replication through many rounds of cell division. In mammals, DNA is replicated in Mb-sized chromosomal units called “replication domains.” While genome-wide maps in multiple cell types and disease states have uncovered both dynamic and static properties of replication domains, we are still in the process of understanding the mechanisms that give rise to these properties. A better understanding of the molecular basis of replication domain regulation will bring new insights into chromosome structure and function.
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21
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Miotto B. Comment l’approche génomique aide à comprendre le processus d’initiation de la réplication. Med Sci (Paris) 2017; 33:143-150. [DOI: 10.1051/medsci/20173302009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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22
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Aladjem MI, Redon CE. Order from clutter: selective interactions at mammalian replication origins. Nat Rev Genet 2017; 18:101-116. [PMID: 27867195 PMCID: PMC6596300 DOI: 10.1038/nrg.2016.141] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Mammalian chromosome duplication progresses in a precise order and is subject to constraints that are often relaxed in developmental disorders and malignancies. Molecular information about the regulation of DNA replication at the chromatin level is lacking because protein complexes that initiate replication seem to bind chromatin indiscriminately. High-throughput sequencing and mathematical modelling have yielded detailed genome-wide replication initiation maps. Combining these maps and models with functional genetic analyses suggests that distinct DNA-protein interactions at subgroups of replication initiation sites (replication origins) modulate the ubiquitous replication machinery and supports an emerging model that delineates how indiscriminate DNA-binding patterns translate into a consistent, organized replication programme.
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Affiliation(s)
- Mirit I Aladjem
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, 37 Convent Drive, Bethesda, Maryland 20892, USA
| | - Christophe E Redon
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, 37 Convent Drive, Bethesda, Maryland 20892, USA
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23
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Raspelli E, Falbo L, Costanzo V. Xenopus egg extract to study regulation of genome-wide and locus-specific DNA replication. Genesis 2017; 55. [PMID: 28095613 DOI: 10.1002/dvg.22996] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2016] [Revised: 11/10/2016] [Accepted: 11/10/2016] [Indexed: 11/10/2022]
Abstract
Faithful DNA replication, coupled with accurate repair of DNA damage, is essential to maintain genome stability and relies on different DNA metabolism genes. Many of these genes are involved in the assembly of replication origins, in the coordination of DNA repair to protect replication forks progression in the presence of DNA damage and in the replication of repetitive chromatin regions. Some DNA metabolism genes are essential in higher eukaryotes, suggesting the existence of specialized mechanisms of repair and replication in organisms with complex genomes. The impact on cell survival of many of these genes has so far precluded in depth molecular analysis of their function. The cell-free Xenopus laevis egg extract represents an ideal system to overcome survival issues and to facilitate the biochemical study of replication-associated functions of essential proteins in vertebrate organisms. Here, we will discuss how Xenopus egg extracts have been used to study cellular and molecular processes, such as DNA replication and DNA repair. In particular, we will focus on innovative imaging and proteomic-based experimental approaches to characterize the molecular function of a number of essential DNA metabolism factors involved in the duplication of complex vertebrate genomes.
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Affiliation(s)
- Erica Raspelli
- DNA metabolism laboratory, IFOM, The FIRC institute for Molecular Oncology, Milan, Italy
| | - Lucia Falbo
- DNA metabolism laboratory, IFOM, The FIRC institute for Molecular Oncology, Milan, Italy
| | - Vincenzo Costanzo
- DNA metabolism laboratory, IFOM, The FIRC institute for Molecular Oncology, Milan, Italy
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24
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Marks AB, Fu H, Aladjem MI. Regulation of Replication Origins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1042:43-59. [PMID: 29357052 DOI: 10.1007/978-981-10-6955-0_2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In eukaryotes, genome duplication starts concomitantly at many replication initiation sites termed replication origins. The replication initiation program is spatially and temporally coordinated to ensure accurate, efficient DNA synthesis that duplicates the entire genome while maintaining other chromatin-dependent functions. Unlike in prokaryotes, not all potential replication origins in eukaryotes are needed for complete genome duplication during each cell cycle. Instead, eukaryotic cells vary the use of initiation sites so that only a fraction of potential replication origins initiate replication each cell cycle. Flexibility in origin choice allows each eukaryotic cell type to utilize different initiation sites, corresponding to unique nuclear DNA packaging patterns. These patterns coordinate replication with gene expression and chromatin condensation. Budding yeast replication origins share a consensus sequence that marks potential initiation sites. Metazoan origins, on the other hand, lack a consensus sequence. Rather, they are associated with a collection of structural features, chromatin packaging features, histone modifications, transcription, and DNA-DNA/DNA-protein interactions. These features confer cell type-specific replication and expression and play an essential role in maintaining genomic stability.
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Affiliation(s)
- Anna B Marks
- Developmental Therapeutics Branch, Center for Cancer Research, NCI, NIH, Bethesda, MD, USA
| | - Haiqing Fu
- Developmental Therapeutics Branch, Center for Cancer Research, NCI, NIH, Bethesda, MD, USA
| | - Mirit I Aladjem
- Developmental Therapeutics Branch, Center for Cancer Research, NCI, NIH, Bethesda, MD, USA.
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25
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Abstract
DNA replication origins strikingly differ between eukaryotic species and cell types. Origins are localized and can be highly efficient in budding yeast, are randomly located in early fly and frog embryos, which do not transcribe their genomes, and are clustered in broad (10-100 kb) non-transcribed zones, frequently abutting transcribed genes, in mammalian cells. Nonetheless, in all cases, origins are established during the G1-phase of the cell cycle by the loading of double hexamers of the Mcm 2-7 proteins (MCM DHs), the core of the replicative helicase. MCM DH activation in S-phase leads to origin unwinding, polymerase recruitment, and initiation of bidirectional DNA synthesis. Although MCM DHs are initially loaded at sites defined by the binding of the origin recognition complex (ORC), they ultimately bind chromatin in much greater numbers than ORC and only a fraction are activated in any one S-phase. Data suggest that the multiplicity and functional redundancy of MCM DHs provide robustness to the replication process and affect replication time and that MCM DHs can slide along the DNA and spread over large distances around the ORC. Recent studies further show that MCM DHs are displaced along the DNA by collision with transcription complexes but remain functional for initiation after displacement. Therefore, eukaryotic DNA replication relies on intrinsically mobile and flexible origins, a strategy fundamentally different from bacteria but conserved from yeast to human. These properties of MCM DHs likely contribute to the establishment of broad, intergenic replication initiation zones in higher eukaryotes.
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Affiliation(s)
- Olivier Hyrien
- Institut de Biologie de l'Ecole Normale Superieure (IBENS), Ecole Normale Superieure, PSL Research University, Paris, France
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26
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Gerhardt J, Bhalla AD, Butler JS, Puckett JW, Dervan PB, Rosenwaks Z, Napierala M. Stalled DNA Replication Forks at the Endogenous GAA Repeats Drive Repeat Expansion in Friedreich's Ataxia Cells. Cell Rep 2016; 16:1218-1227. [PMID: 27425605 PMCID: PMC5028224 DOI: 10.1016/j.celrep.2016.06.075] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Revised: 05/31/2016] [Accepted: 06/17/2016] [Indexed: 10/21/2022] Open
Abstract
Friedreich's ataxia (FRDA) is caused by the expansion of GAA repeats located in the Frataxin (FXN) gene. The GAA repeats continue to expand in FRDA patients, aggravating symptoms and contributing to disease progression. The mechanism leading to repeat expansion and decreased FXN transcription remains unclear. Using single-molecule analysis of replicated DNA, we detected that expanded GAA repeats present a substantial obstacle for the replication machinery at the FXN locus in FRDA cells. Furthermore, aberrant origin activation and lack of a proper stress response to rescue the stalled forks in FRDA cells cause an increase in 3'-5' progressing forks, which could enhance repeat expansion and hinder FXN transcription by head-on collision with RNA polymerases. Treatment of FRDA cells with GAA-specific polyamides rescues DNA replication fork stalling and alleviates expansion of the GAA repeats, implicating DNA triplexes as a replication impediment and suggesting that fork stalling might be a therapeutic target for FRDA.
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Affiliation(s)
- Jeannine Gerhardt
- Center for Reproductive Medicine, Weill Cornell Medical College, New York, NY 10065, USA.
| | - Angela D Bhalla
- Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama, Birmingham, AL 35294, USA
| | - Jill Sergesketter Butler
- Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama, Birmingham, AL 35294, USA
| | - James W Puckett
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Peter B Dervan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Zev Rosenwaks
- Center for Reproductive Medicine, Weill Cornell Medical College, New York, NY 10065, USA
| | - Marek Napierala
- Department of Biochemistry and Molecular Genetics, UAB Stem Cell Institute, University of Alabama, Birmingham, AL 35294, USA; Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan 61 704, Poland.
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27
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Stevanoni M, Palumbo E, Russo A. The Replication of Frataxin Gene Is Assured by Activation of Dormant Origins in the Presence of a GAA-Repeat Expansion. PLoS Genet 2016; 12:e1006201. [PMID: 27447727 PMCID: PMC4957762 DOI: 10.1371/journal.pgen.1006201] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Accepted: 06/27/2016] [Indexed: 12/17/2022] Open
Abstract
It is well known that DNA replication affects the stability of several trinucleotide repeats, but whether replication profiles of human loci carrying an expanded repeat differ from those of normal alleles is poorly understood in the endogenous context. We investigated this issue using cell lines from Friedreich's ataxia patients, homozygous for a GAA-repeat expansion in intron 1 of the Frataxin gene. By interphase, FISH we found that in comparison to the normal Frataxin sequence the replication of expanded alleles is slowed or delayed. According to molecular combing, origins never fired within the normal Frataxin allele. In contrast, in mutant alleles dormant origins are recruited within the gene, causing a switch of the prevalent fork direction through the expanded repeat. Furthermore, a global modification of the replication profile, involving origin choice and a differential distribution of unidirectional forks, was observed in the surrounding 850 kb region. These data provide a wide-view of the interplay of events occurring during replication of genes carrying an expanded repeat.
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Affiliation(s)
| | - Elisa Palumbo
- Department of Biology, University of Padova, Padova, Italy
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28
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Kenigsberg E, Yehuda Y, Marjavaara L, Keszthelyi A, Chabes A, Tanay A, Simon I. The mutation spectrum in genomic late replication domains shapes mammalian GC content. Nucleic Acids Res 2016; 44:4222-32. [PMID: 27085808 PMCID: PMC4872117 DOI: 10.1093/nar/gkw268] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Revised: 03/10/2016] [Accepted: 03/30/2016] [Indexed: 11/14/2022] Open
Abstract
Genome sequence compositions and epigenetic organizations are correlated extensively across multiple length scales. Replication dynamics, in particular, is highly correlated with GC content. We combine genome-wide time of replication (ToR) data, topological domains maps and detailed functional epigenetic annotations to study the correlations between replication timing and GC content at multiple scales. We find that the decrease in genomic GC content at large scale late replicating regions can be explained by mutation bias favoring A/T nucleotide, without selection or biased gene conversion. Quantification of the free dNTP pool during the cell cycle is consistent with a mechanism involving replication-coupled mutation spectrum that favors AT nucleotides at late S-phase. We suggest that mammalian GC content composition is shaped by independent forces, globally modulating mutation bias and locally selecting on functional element. Deconvoluting these forces and analyzing them on their native scales is important for proper characterization of complex genomic correlations.
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Affiliation(s)
- Ephraim Kenigsberg
- Department of Computer Science and Applied Mathematics, Weizmann Institute of Science, Rehovot, Israel
| | - Yishai Yehuda
- Department of Microbiology and Molecular Genetics, IMRIC, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Lisette Marjavaara
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden
| | - Andrea Keszthelyi
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden
| | - Andrei Chabes
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden
| | - Amos Tanay
- Department of Computer Science and Applied Mathematics, Weizmann Institute of Science, Rehovot, Israel
| | - Itamar Simon
- Department of Microbiology and Molecular Genetics, IMRIC, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
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29
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Drosopoulos WC, Kosiyatrakul ST, Schildkraut CL. BLM helicase facilitates telomere replication during leading strand synthesis of telomeres. J Cell Biol 2016. [PMID: 26195664 PMCID: PMC4508891 DOI: 10.1083/jcb.201410061] [Citation(s) in RCA: 110] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
BLM helicase facilitates telomere replication by resolving G-quadruplex structures that can form in the G-rich repeats during leading strand synthesis. Based on its in vitro unwinding activity on G-quadruplex (G4) DNA, the Bloom syndrome–associated helicase BLM is proposed to participate in telomere replication by aiding fork progression through G-rich telomeric DNA. Single molecule analysis of replicated DNA (SMARD) was used to determine the contribution of BLM helicase to telomere replication. In BLM-deficient cells, replication forks initiating from origins within the telomere, which copy the G-rich strand by leading strand synthesis, moved slower through the telomere compared with the adjacent subtelomere. Fork progression through the telomere was further slowed in the presence of a G4 stabilizer. Using a G4-specific antibody, we found that deficiency of BLM, or another G4-unwinding helicase, the Werner syndrome-associated helicase WRN, resulted in increased G4 structures in cells. Importantly, deficiency of either helicase led to greater increases in G4 DNA detected in the telomere compared with G4 seen genome-wide. Collectively, our findings are consistent with BLM helicase facilitating telomere replication by resolving G4 structures formed during copying of the G-rich strand by leading strand synthesis.
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Affiliation(s)
| | | | - Carl L Schildkraut
- Department of Cell Biology, Albert Einstein College of Medicine, New York, NY 10461
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30
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Marks AB, Smith OK, Aladjem MI. Replication origins: determinants or consequences of nuclear organization? Curr Opin Genet Dev 2016; 37:67-75. [PMID: 26845042 PMCID: PMC4914405 DOI: 10.1016/j.gde.2015.11.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Revised: 11/24/2015] [Accepted: 11/25/2015] [Indexed: 12/20/2022]
Abstract
Chromosome replication, gene expression and chromatin assembly all occur on the same template, necessitating a tight spatial and temporal coordination to maintain genomic stability. The distribution of replication initiation events is responsive to local and global changes in chromatin structure and is affected by transcriptional activity. Concomitantly, replication origin sequences, which determine the locations of replication initiation events, can affect chromatin structure and modulate transcriptional efficiency. The flexibility observed in the replication initiation landscape might help achieve complete and accurate genome duplication while coordinating the DNA replication program with transcription and other nuclear processes in a cell-type specific manner. This review discusses the relationships among replication origin distribution, local and global chromatin structures and concomitant nuclear metabolic processes.
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Affiliation(s)
- Anna B Marks
- Developmental Therapeutics Branch, NCI, NIH, Bethesda, MD, USA
| | - Owen K Smith
- Developmental Therapeutics Branch, NCI, NIH, Bethesda, MD, USA
| | - Mirit I Aladjem
- Developmental Therapeutics Branch, NCI, NIH, Bethesda, MD, USA.
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Pilzecker B, Buoninfante OA, Pritchard C, Blomberg OS, Huijbers IJ, van den Berk PCM, Jacobs H. PrimPol prevents APOBEC/AID family mediated DNA mutagenesis. Nucleic Acids Res 2016; 44:4734-44. [PMID: 26926109 PMCID: PMC4889928 DOI: 10.1093/nar/gkw123] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 02/19/2016] [Indexed: 01/09/2023] Open
Abstract
PrimPol is a DNA damage tolerant polymerase displaying both translesion synthesis (TLS) and (re)-priming properties. This led us to study the consequences of a PrimPol deficiency in tolerating mutagenic lesions induced by members of the APOBEC/AID family of cytosine deaminases. Interestingly, during somatic hypermutation, PrimPol counteracts the generation of C>G transversions on the leading strand. Independently, mutation analyses in human invasive breast cancer confirmed a pro-mutagenic activity of APOBEC3B and revealed a genome-wide anti-mutagenic activity of PRIMPOL as well as most Y-family TLS polymerases. PRIMPOL especially prevents APOBEC3B targeted cytosine mutations within TpC dinucleotides. As C transversions induced by APOBEC/AID family members depend on the formation of AP-sites, we propose that PrimPol reprimes preferentially downstream of AP-sites on the leading strand, to prohibit error-prone TLS and simultaneously stimulate error-free homology directed repair. These in vivo studies are the first demonstrating a critical anti-mutagenic activity of PrimPol in genome maintenance.
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Affiliation(s)
- Bas Pilzecker
- Division of Biological Stress Response, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Olimpia Alessandra Buoninfante
- Division of Biological Stress Response, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Colin Pritchard
- Mouse Clinic for Cancer and Aging research (MCCA) Transgenic Facility, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Olga S Blomberg
- Division of Biological Stress Response, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Ivo J Huijbers
- Mouse Clinic for Cancer and Aging research (MCCA) Transgenic Facility, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Paul C M van den Berk
- Division of Biological Stress Response, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Heinz Jacobs
- Division of Biological Stress Response, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
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Dileep V, Rivera-Mulia JC, Sima J, Gilbert DM. Large-Scale Chromatin Structure-Function Relationships during the Cell Cycle and Development: Insights from Replication Timing. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2015; 80:53-63. [PMID: 26590169 DOI: 10.1101/sqb.2015.80.027284] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Chromosome architecture has received a lot of attention since the recent development of genome-scale methods to measure chromatin interactions (Hi-C), enabling the first sequence-based models of chromosome tertiary structure. A view has emerged of chromosomes as a string of structural units (topologically associating domains; TADs) whose boundaries persist through the cell cycle and development. TADs with similar chromatin states tend to aggregate, forming spatially segregated chromatin compartments. However, high-resolution Hi-C has revealed substructure within TADs (subTADs) that poses a challenge for models that attribute significance to structural units at any given scale. More than 20 years ago, the DNA replication field independently identified stable structural (and functional) units of chromosomes (replication foci) as well as spatially segregated chromatin compartments (early and late foci), but lacked the means to link these units to genomic map units. Genome-wide studies of replication timing (RT) have now merged these two disciplines by identifying individual units of replication regulation (replication domains; RDs) that correspond to TADs and are arranged in 3D to form spatiotemporally segregated subnuclear compartments. Furthermore, classifying RDs/TADs by their constitutive versus developmentally regulated RT has revealed distinct classes of chromatin organization, providing unexpected insight into the relationship between large-scale chromosome structure and function.
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Affiliation(s)
- Vishnu Dileep
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306-4295
| | | | - Jiao Sima
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306-4295
| | - David M Gilbert
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306-4295 Center for Genomics and Personalized Medicine, Florida State University, Tallahassee, Florida 32306-4295
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Alvarez S, Díaz M, Flach J, Rodriguez-Acebes S, López-Contreras AJ, Martínez D, Cañamero M, Fernández-Capetillo O, Isern J, Passegué E, Méndez J. Replication stress caused by low MCM expression limits fetal erythropoiesis and hematopoietic stem cell functionality. Nat Commun 2015; 6:8548. [PMID: 26456157 PMCID: PMC4608254 DOI: 10.1038/ncomms9548] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2015] [Accepted: 09/04/2015] [Indexed: 01/04/2023] Open
Abstract
Replicative stress during embryonic development influences ageing and predisposition to disease in adults. A protective mechanism against replicative stress is provided by the licensing of thousands of origins in G1 that are not necessarily activated in the subsequent S-phase. These ‘dormant' origins provide a backup in the presence of stalled forks and may confer flexibility to the replication program in specific cell types during differentiation, a role that has remained unexplored. Here we show, using a mouse strain with hypomorphic expression of the origin licensing factor mini-chromosome maintenance (MCM)3 that limiting origin licensing in vivo affects the functionality of hematopoietic stem cells and the differentiation of rapidly-dividing erythrocyte precursors. Mcm3-deficient erythroblasts display aberrant DNA replication patterns and fail to complete maturation, causing lethal anemia. Our results indicate that hematopoietic progenitors are particularly sensitive to replication stress, and full origin licensing ensures their correct differentiation and functionality. What causes hematopoietic stem cell loss of functionality? Here, Alvarez et al. show that loss of origin licensing factor MCM3 induces replicative stress (RS), causing aberrant erythrocyte maturation, but mice strains with higher tolerance to RS can overcome this defect.
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Affiliation(s)
- Silvia Alvarez
- DNA Replication Group, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro, 3, 28029 Madrid, Spain
| | - Marcos Díaz
- DNA Replication Group, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro, 3, 28029 Madrid, Spain
| | - Johanna Flach
- The Eli and Edythe Broad Center for Regeneration Medicine and Stem Cell Research, UCSF, San Francisco, 94143 California, USA
| | - Sara Rodriguez-Acebes
- DNA Replication Group, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro, 3, 28029 Madrid, Spain
| | - Andrés J López-Contreras
- Genomic Instability Group, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro, 3, 28029 Madrid, Spain
| | - Dolores Martínez
- Flow Cytometry Unit, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro, 3, 28029 Madrid, Spain
| | - Marta Cañamero
- Compared Pathology Unit, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro, 3, 28029 Madrid, Spain
| | - Oscar Fernández-Capetillo
- Genomic Instability Group, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro, 3, 28029 Madrid, Spain
| | - Joan Isern
- Spanish National Cardiovascular Research Center (CNIC), Melchor Fernández Almagro, 3, 28029 Madrid, Spain
| | - Emmanuelle Passegué
- The Eli and Edythe Broad Center for Regeneration Medicine and Stem Cell Research, UCSF, San Francisco, 94143 California, USA
| | - Juan Méndez
- DNA Replication Group, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro, 3, 28029 Madrid, Spain
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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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Nordman JT, Orr-Weaver TL. Understanding replication fork progression, stability, and chromosome fragility by exploiting the Suppressor of Underreplication protein. Bioessays 2015; 37:856-61. [PMID: 26059810 DOI: 10.1002/bies.201500021] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
There are many layers of regulation governing DNA replication to ensure that genetic information is accurately transmitted from mother cell to daughter cell. While much of the control occurs at the level of origin selection and firing, less is known about how replication fork progression is controlled throughout the genome. In Drosophila polytene cells, specific regions of the genome become repressed for DNA replication, resulting in underreplication and decreased copy number. Importantly, underreplicated domains share properties with common fragile sites. The Suppressor of Underreplication protein SUUR is essential for this repression. Recent work established that SUUR functions by directly inhibiting replication fork progression, raising several interesting questions as to how replication fork progression and stability can be modulated within targeted regions of the genome. Here we discuss potential mechanisms by which replication fork inhibition can be achieved and the consequences this has on genome stability and copy number control.
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Affiliation(s)
- Jared T Nordman
- Department of Biology, Whitehead Institute, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Terry L Orr-Weaver
- Department of Biology, Whitehead Institute, Massachusetts Institute of Technology, Cambridge, MA, USA
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Rivera-Mulia JC, Buckley Q, Sasaki T, Zimmerman J, Didier RA, Nazor K, Loring JF, Lian Z, Weissman S, Robins AJ, Schulz TC, Menendez L, Kulik MJ, Dalton S, Gabr H, Kahveci T, Gilbert DM. Dynamic changes in replication timing and gene expression during lineage specification of human pluripotent stem cells. Genome Res 2015; 25:1091-103. [PMID: 26055160 PMCID: PMC4509994 DOI: 10.1101/gr.187989.114] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 06/05/2015] [Indexed: 12/31/2022]
Abstract
Duplication of the genome in mammalian cells occurs in a defined temporal order referred to as its replication-timing (RT) program. RT changes dynamically during development, regulated in units of 400-800 kb referred to as replication domains (RDs). Changes in RT are generally coordinated with transcriptional competence and changes in subnuclear position. We generated genome-wide RT profiles for 26 distinct human cell types, including embryonic stem cell (hESC)-derived, primary cells and established cell lines representing intermediate stages of endoderm, mesoderm, ectoderm, and neural crest (NC) development. We identified clusters of RDs that replicate at unique times in each stage (RT signatures) and confirmed global consolidation of the genome into larger synchronously replicating segments during differentiation. Surprisingly, transcriptome data revealed that the well-accepted correlation between early replication and transcriptional activity was restricted to RT-constitutive genes, whereas two-thirds of the genes that switched RT during differentiation were strongly expressed when late replicating in one or more cell types. Closer inspection revealed that transcription of this class of genes was frequently restricted to the lineage in which the RT switch occurred, but was induced prior to a late-to-early RT switch and/or down-regulated after an early-to-late RT switch. Analysis of transcriptional regulatory networks showed that this class of genes contains strong regulators of genes that were only expressed when early replicating. These results provide intriguing new insight into the complex relationship between transcription and RT regulation during human development.
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Affiliation(s)
- Juan Carlos Rivera-Mulia
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306-4295, USA
| | - Quinton Buckley
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306-4295, USA
| | - Takayo Sasaki
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306-4295, USA
| | - Jared Zimmerman
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306-4295, USA
| | - Ruth A Didier
- College of Medicine, Florida State University, Tallahassee, Florida 32306-4295, USA
| | - Kristopher Nazor
- Center for Regenerative Medicine, Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California 92037, USA
| | - Jeanne F Loring
- Center for Regenerative Medicine, Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California 92037, USA
| | - Zheng Lian
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut 06519, USA
| | - Sherman Weissman
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut 06519, USA
| | | | | | - Laura Menendez
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602, USA
| | - Michael J Kulik
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602, USA
| | - Stephen Dalton
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602, USA
| | - Haitham Gabr
- Department of Computer and Information Sciences and Engineering, University of Florida, Gainesville, Florida 32611, USA
| | - Tamer Kahveci
- Department of Computer and Information Sciences and Engineering, University of Florida, Gainesville, Florida 32611, USA
| | - David M Gilbert
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306-4295, USA; Center for Genomics and Personalized Medicine, Florida State University, Tallahassee, Florida 32306, USA
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Sherstyuk VV, Shevchenko AI, Zakian SM. Mapping of Replication Origins in the X Inactivation Center of Vole Microtus levis Reveals Extended Replication Initiation Zone. PLoS One 2015; 10:e0128497. [PMID: 26038842 PMCID: PMC4454516 DOI: 10.1371/journal.pone.0128497] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Accepted: 04/27/2015] [Indexed: 11/29/2022] Open
Abstract
DNA replication initiates at specific positions termed replication origins. Genome-wide studies of human replication origins have shown that origins are organized into replication initiation zones. However, only few replication initiation zones have been described so far. Moreover, few origins were mapped in other mammalian species besides human and mouse. Here we analyzed pattern of short nascent strands in the X inactivation center (XIC) of vole Microtus levis in fibroblasts, trophoblast stem cells, and extraembryonic endoderm stem cells and confirmed origins locations by ChIP approach. We found that replication could be initiated in a significant part of XIC. We also analyzed state of XIC chromatin in these cell types. We compared origin localization in the mouse and vole XIC. Interestingly, origins associated with gene promoters are conserved in these species. The data obtained allow us to suggest that the X inactivation center of M. levis is one extended replication initiation zone.
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Affiliation(s)
- Vladimir V. Sherstyuk
- Institute of Cytology and Genetics, Russian Academy of Sciences, Siberian Branch, Novosibirsk, Russia
- State Research Institute of Circulation Pathology, Novosibirsk, Russia
- Institute of Chemical Biology and Fundamental Medicine, Russian Academy of Sciences, Siberian Branch, Novosibirsk, Russia
| | - Alexander I. Shevchenko
- Institute of Cytology and Genetics, Russian Academy of Sciences, Siberian Branch, Novosibirsk, Russia
- State Research Institute of Circulation Pathology, Novosibirsk, Russia
- Institute of Chemical Biology and Fundamental Medicine, Russian Academy of Sciences, Siberian Branch, Novosibirsk, Russia
| | - Suren M. Zakian
- Institute of Cytology and Genetics, Russian Academy of Sciences, Siberian Branch, Novosibirsk, Russia
- State Research Institute of Circulation Pathology, Novosibirsk, Russia
- Institute of Chemical Biology and Fundamental Medicine, Russian Academy of Sciences, Siberian Branch, Novosibirsk, Russia
- Novosibirsk State University, Novosibirsk, Russia
- * E-mail:
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Bartholdy B, Mukhopadhyay R, Lajugie J, Aladjem MI, Bouhassira EE. Allele-specific analysis of DNA replication origins in mammalian cells. Nat Commun 2015; 6:7051. [PMID: 25987481 PMCID: PMC4479011 DOI: 10.1038/ncomms8051] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 03/26/2015] [Indexed: 01/01/2023] Open
Abstract
The mechanisms that control the location and timing of firing of replication origins are poorly understood. Using a novel functional genomic approach based on the analysis of SNPs and indels in phased human genomes, we observe that replication asynchrony is associated with small cumulative variations in the initiation efficiency of multiple origins between the chromosome homologues, rather than with the activation of dormant origins. Allele-specific measurements demonstrate that the presence of G-quadruplex-forming sequences does not correlate with the efficiency of initiation. Sequence analysis reveals that the origins are highly enriched in sequences with profoundly asymmetric G/C and A/T nucleotide distributions and are almost completely depleted of antiparallel triplex-forming sequences. We therefore propose that although G4-forming sequences are abundant in replication origins, an asymmetry in nucleotide distribution, which increases the propensity of origins to unwind and adopt non-B DNA structure, rather than the ability to form G4, is directly associated with origin activity.
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Affiliation(s)
- Boris Bartholdy
- Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, USA
| | - Rituparna Mukhopadhyay
- Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, USA
| | - Julien Lajugie
- Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, USA
| | - Mirit I. Aladjem
- Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, 37 Convent Drive, Bethesda, Maryland 20892, USA
| | - Eric E. Bouhassira
- Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, USA
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He M, Cortizas EM, Verdun RE, Severinson E. Cyclin-dependent kinases regulate Ig class switching by controlling access of AID to the switch region. THE JOURNAL OF IMMUNOLOGY 2015; 194:4231-9. [PMID: 25795757 DOI: 10.4049/jimmunol.1402146] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Accepted: 02/05/2015] [Indexed: 01/08/2023]
Abstract
Ig class switching requires cell proliferation and is division linked, but the detailed mechanism is unknown. By analyzing the first switching cells early in the kinetics, our analysis suggested that proliferating B cells had a very short G1 phase (<3.5 h), a total cell cycle time of ∼ 11 h, and that Ig class switching preferentially occurred in the late G1 or early S phase. Inhibition of cyclin-dependent kinases (CDKs) caused dramatic reduction of switching rate within 6 h. This was associated with less targeting of activation-induced cytidine deaminase (AID) to the Igh locus. Interestingly, ectopically expressed nuclear AID in HeLa cells was preferentially found in the early S phase. Furthermore, in CDK2 hypomorphic cells there was reduced nuclear AID accumulation. Thus, our data are compatible with the idea that division-linked Ig class switching is in part due to CDK2-regulated AID nuclear access at the G1/S border.
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Affiliation(s)
- Minghui He
- Department of Molecular Biosciences, Wenner-Gren Institute, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Elena M Cortizas
- Division of Gerontology and Geriatric Medicine, Department of Medicine, Miller School of Medicine, University of Miami, Miami, FL 33136
| | - Ramiro E Verdun
- Division of Gerontology and Geriatric Medicine, Department of Medicine, Miller School of Medicine, University of Miami, Miami, FL 33136; Sylvester Comprehensive Cancer Center, University of Miami, Miami, FL 33136; and Geriatric Research, Education, and Clinical Center, Miami Veterans Affairs Healthcare System, Miami, FL 33125
| | - Eva Severinson
- Department of Molecular Biosciences, Wenner-Gren Institute, Stockholm University, SE-106 91 Stockholm, Sweden;
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40
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Dellino GI, Pelicci PG. Next-generation sequencing and DNA replication in human cells: the future has arrived. Future Oncol 2015; 10:683-93. [PMID: 24754597 DOI: 10.2217/fon.13.182] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Accurate regulation of DNA replication ensures faithful transmission of eukaryotic genomes and maintenance of genomic stability and chromatin organization. However, by itself the replication process is a threat for both DNA and chromatin integrity. This becomes particularly relevant in cancer cells, where activated oncogenes induce replication-stress, including unscheduled initiation, fork stalling and collapse and, ultimately, genomic instability. Studies addressing the relationship between (epi)genome integrity and disease have been hampered by our poor knowledge of the mechanisms regulating where and when eukaryotic replication initiates. Recently developed genome-scale methods for the analysis of DNA replication in mammals will contribute to the identification of missing links between replication, chromatin regulation and genome stability in normal and cancer cells.
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Affiliation(s)
- Gaetano Ivan Dellino
- Department of Experimental Oncology, European Institute of Oncology, 20141 Milan, Italy
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41
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Hyrien O. Peaks cloaked in the mist: the landscape of mammalian replication origins. J Cell Biol 2015; 208:147-60. [PMID: 25601401 PMCID: PMC4298691 DOI: 10.1083/jcb.201407004] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 12/16/2014] [Indexed: 12/23/2022] Open
Abstract
Replication of mammalian genomes starts at sites termed replication origins, which historically have been difficult to locate as a result of large genome sizes, limited power of genetic identification schemes, and rareness and fragility of initiation intermediates. However, origins are now mapped by the thousands using microarrays and sequencing techniques. Independent studies show modest concordance, suggesting that mammalian origins can form at any DNA sequence but are suppressed by read-through transcription or that they can overlap the 5' end or even the entire gene. These results require a critical reevaluation of whether origins form at specific DNA elements and/or epigenetic signals or require no such determinants.
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Affiliation(s)
- Olivier Hyrien
- Institut de Biologie de l'Ecole Normale Supérieure, Centre National de la Recherche Scientifique UMR8197 and Institut National de la Santé et de la Recherche Médicale U1024, 75005 Paris, France
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42
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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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43
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Besnard E, Desprat R, Ryan M, Kahli M, Aladjem MI, Lemaitre JM. Best practices for mapping replication origins in eukaryotic chromosomes. ACTA ACUST UNITED AC 2014; 64:22.18.1-13. [PMID: 25181303 DOI: 10.1002/0471143030.cb2218s64] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Understanding the regulatory principles ensuring complete DNA replication in each cell division is critical for deciphering the mechanisms that maintain genomic stability. Recent advances in genome sequencing technology facilitated complete mapping of DNA replication sites and helped move the field from observing replication patterns at a handful of single loci to analyzing replication patterns genome-wide. These advances address issues, such as the relationship between replication initiation events, transcription, and chromatin modifications, and identify potential replication origin consensus sequences. This unit summarizes the technological and fundamental aspects of replication profiling and briefly discusses novel insights emerging from mining large datasets, published in the last 3 years, and also describes DNA replication dynamics on a whole-genome scale.
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Affiliation(s)
- Emilie Besnard
- Laboratory of Genome Plasticity and Aging, Institute of Functional Genomics, CNRS UMR5203, INSERM U661, UMI, Montpellier, France
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Mukhopadhyay R, Lajugie J, Fourel N, Selzer A, Schizas M, Bartholdy B, Mar J, Lin CM, Martin MM, Ryan M, Aladjem MI, Bouhassira EE. Allele-specific genome-wide profiling in human primary erythroblasts reveal replication program organization. PLoS Genet 2014; 10:e1004319. [PMID: 24787348 PMCID: PMC4006724 DOI: 10.1371/journal.pgen.1004319] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Accepted: 03/10/2014] [Indexed: 11/19/2022] Open
Abstract
We have developed a new approach to characterize allele-specific timing of DNA replication genome-wide in human primary basophilic erythroblasts. We show that the two chromosome homologs replicate at the same time in about 88% of the genome and that large structural variants are preferentially associated with asynchronous replication. We identified about 600 megabase-sized asynchronously replicated domains in two tested individuals. The longest asynchronously replicated domains are enriched in imprinted genes suggesting that structural variants and parental imprinting are two causes of replication asynchrony in the human genome. Biased chromosome X inactivation in one of the two individuals tested was another source of detectable replication asynchrony. Analysis of high-resolution TimEX profiles revealed small variations termed timing ripples, which were undetected in previous, lower resolution analyses. Timing ripples reflect highly reproducible, variations of the timing of replication in the 100 kb-range that exist within the well-characterized megabase-sized replication timing domains. These ripples correspond to clusters of origins of replication that we detected using novel nascent strands DNA profiling methods. Analysis of the distribution of replication origins revealed dramatic differences in initiation of replication frequencies during S phase and a strong association, in both synchronous and asynchronous regions, between origins of replication and three genomic features: G-quadruplexes, CpG Islands and transcription start sites. The frequency of initiation in asynchronous regions was similar in the two homologs. Asynchronous regions were richer in origins of replication than synchronous regions. DNA replication in mammalian cells proceeds according to a distinct order. Genes that are expressed tend to replicate before genes that are not expressed. We report here that we have developed a method to measure the timing of replication of the maternal and paternal chromosomes separately. We found that the paternal and maternal chromosomes replicate at exactly the same time in the large majority of the genome and that the 12% of the genome that replicated asynchronously was enriched in imprinted genes and in structural variants. Previous experiments have shown that chromosomes could be divided into replication timing domains that are a few hundred thousand to a few megabases in size. We show here that these domains can be divided into sub-domains defined by ripples in the timing profile. These ripples corresponded to clusters of origins of replication. Finally, we show that the frequency of initiation in asynchronous regions was similar in the two homologs.
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Affiliation(s)
- Rituparna Mukhopadhyay
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Julien Lajugie
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Nicolas Fourel
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Ari Selzer
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Michael Schizas
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Boris Bartholdy
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Jessica Mar
- Department of Systems and Computational Biology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Chii Mei Lin
- Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America
| | - Melvenia M. Martin
- Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America
| | - Michael Ryan
- Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America
| | - Mirit I. Aladjem
- Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America
| | - Eric E. Bouhassira
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York, United States of America
- * E-mail:
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Abstract
While large portions of the mammalian genome are known to replicate sequentially in a distinct, tissue-specific order, recent studies suggest that the inactive X chromosome is duplicated rapidly via random, synchronous DNA synthesis at numerous adjacent regions. The rapid duplication of the inactive X chromosome was observed in high-resolution studies visualizing DNA replication patterns in the nucleus, and by allele-specific DNA sequencing studies measuring the extent of DNA synthesis. These studies conclude that inactive X chromosomes complete replication earlier than previously thought and suggest that the strict order of DNA replication detected in the majority of genomic regions is not preserved in non-transcribed, "silent" chromatin. These observations alter current concepts about the regulation of DNA replication in non-transcribed portions of the genome in general and in the inactive X-chromosome in particular.
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Affiliation(s)
- Mirit I Aladjem
- Developmental Therapeutic Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA
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Sherstyuk VV, Shevchenko AI, Zakian SM. Epigenetic landscape for initiation of DNA replication. Chromosoma 2013; 123:183-99. [PMID: 24337246 DOI: 10.1007/s00412-013-0448-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Revised: 11/27/2013] [Accepted: 12/02/2013] [Indexed: 02/07/2023]
Abstract
The key genetic process of DNA replication is initiated at specific sites referred to as replication origins. In eukaryotes, origins of DNA replication are not specified by a defined nucleotide sequence. Recent studies have shown that the structural context and topology of DNA sequence, chromatin features, and its transcriptional activity play an important role in origin choice. During differentiation and development, significant changes in chromatin organization and transcription occur, influencing origin activity and choice. In the last few years, a number of different genome-wide studies have broadened the understanding of replication origin regulation. In this review, we discuss the epigenetic factors and mechanisms that modulate origin choice and firing.
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Affiliation(s)
- Vladimir V Sherstyuk
- Russian Academy of Sciences, Siberian Branch, Institute of Cytology and Genetics, pr. Akad. Lavrentieva 10, Novosibirsk, 630090, Russia
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Gerhardt J, Tomishima MJ, Zaninovic N, Colak D, Yan Z, Zhan Q, Rosenwaks Z, Jaffrey SR, Schildkraut CL. The DNA replication program is altered at the FMR1 locus in fragile X embryonic stem cells. Mol Cell 2013; 53:19-31. [PMID: 24289922 DOI: 10.1016/j.molcel.2013.10.029] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Revised: 09/04/2013] [Accepted: 10/23/2013] [Indexed: 01/17/2023]
Abstract
Fragile X syndrome (FXS) is caused by a CGG repeat expansion in the FMR1 gene that appears to occur during oogenesis and during early embryogenesis. One model proposes that repeat instability depends on the replication fork direction through the repeats such that (CNG)n hairpin-like structures form, causing DNA polymerase to stall and slip. Examining DNA replication fork progression on single DNA molecules at the endogenous FMR1 locus revealed that replication forks stall at CGG repeats in human cells. Furthermore, replication profiles of FXS human embryonic stem cells (hESCs) compared to nonaffected hESCs showed that fork direction through the repeats is altered at the FMR1 locus in FXS hESCs, such that predominantly the CCG strand serves as the lagging-strand template. This is due to the absence of replication initiation that would typically occur upstream of FMR1, suggesting that altered replication origin usage combined with fork stalling promotes repeat instability during early embryonic development.
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Affiliation(s)
- Jeannine Gerhardt
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | - Mark J Tomishima
- SKI Stem Cell Research Facility, Sloan-Kettering Institute, New York, NY 10065, USA
| | - Nikica Zaninovic
- Center for Reproductive Medicine and Infertility, Weill Cornell Medical College, New York, NY 10065, USA
| | - Dilek Colak
- Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065, USA
| | - Zi Yan
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Qiansheng Zhan
- Center for Reproductive Medicine and Infertility, Weill Cornell Medical College, New York, NY 10065, USA
| | - Zev Rosenwaks
- Center for Reproductive Medicine and Infertility, Weill Cornell Medical College, New York, NY 10065, USA
| | - Samie R Jaffrey
- Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065, USA
| | - Carl L Schildkraut
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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Abstract
The onset of genomic DNA synthesis requires precise interactions of specialized initiator proteins with DNA at sites where the replication machinery can be loaded. These sites, defined as replication origins, are found at a few unique locations in all of the prokaryotic chromosomes examined so far. However, replication origins are dispersed among tens of thousands of loci in metazoan chromosomes, thereby raising questions regarding the role of specific nucleotide sequences and chromatin environment in origin selection and the mechanisms used by initiators to recognize replication origins. Close examination of bacterial and archaeal replication origins reveals an array of DNA sequence motifs that position individual initiator protein molecules and promote initiator oligomerization on origin DNA. Conversely, the need for specific recognition sequences in eukaryotic replication origins is relaxed. In fact, the primary rule for origin selection appears to be flexibility, a feature that is modulated either by structural elements or by epigenetic mechanisms at least partly linked to the organization of the genome for gene expression.
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Affiliation(s)
- Alan C Leonard
- Department of Biological Sciences, Florida Institute of Technology, Melbourne, Florida 32901
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Belan E. LINEs of evidence: noncanonical DNA replication as an epigenetic determinant. Biol Direct 2013; 8:22. [PMID: 24034780 PMCID: PMC3868326 DOI: 10.1186/1745-6150-8-22] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 09/06/2013] [Indexed: 12/17/2022] Open
Abstract
LINE-1 (L1) retrotransposons are repetitive elements in mammalian genomes. They are
capable of synthesizing DNA on their own RNA templates by harnessing reverse
transcriptase (RT) that they encode. Abundantly expressed full-length L1s and their
RT are found to globally influence gene expression profiles, differentiation state,
and proliferation capacity of early embryos and many types of cancer, albeit by yet
unknown mechanisms. They are essential for the progression of early development and
the establishment of a cancer-related undifferentiated state. This raises important
questions regarding the functional significance of L1 RT in these cell systems.
Massive nuclear L1-linked reverse transcription has been shown to occur in mouse
zygotes and two-cell embryos, and this phenomenon is purported to be DNA replication
independent. This review argues against this claim with the goal of understanding the
nature of this phenomenon and the role of L1 RT in early embryos and cancers.
Available L1 data are revisited and integrated with relevant findings accumulated in
the fields of replication timing, chromatin organization, and epigenetics, bringing
together evidence that strongly supports two new concepts. First, noncanonical
replication of a portion of genomic full-length L1s by means of L1 RNP-driven reverse
transcription is proposed to co-exist with DNA polymerase-dependent replication of
the rest of the genome during the same round of DNA replication in embryonic and
cancer cell systems. Second, the role of this mechanism is thought to be epigenetic;
it might promote transcriptional competence of neighboring genes linked to
undifferentiated states through the prevention of tethering of involved L1s to the
nuclear periphery. From the standpoint of these concepts, several hitherto
inexplicable phenomena can be explained. Testing methods for the model are
proposed.
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Affiliation(s)
- Ekaterina Belan
- Genetics Laboratory, Royal University Hospital, Saskatoon, SK S7N 0W8, Canada.
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50
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Replication timing regulation of eukaryotic replicons: Rif1 as a global regulator of replication timing. Trends Genet 2013; 29:449-60. [DOI: 10.1016/j.tig.2013.05.001] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Revised: 04/27/2013] [Accepted: 05/01/2013] [Indexed: 12/13/2022]
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