1
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Piguet B, Houseley J. Transcription as source of genetic heterogeneity in budding yeast. Yeast 2024; 41:171-185. [PMID: 38196235 DOI: 10.1002/yea.3926] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2023] [Revised: 12/10/2023] [Accepted: 12/20/2023] [Indexed: 01/11/2024] Open
Abstract
Transcription presents challenges to genome stability both directly, by altering genome topology and exposing single-stranded DNA to chemical insults and nucleases, and indirectly by introducing obstacles to the DNA replication machinery. Such obstacles include the RNA polymerase holoenzyme itself, DNA-bound regulatory factors, G-quadruplexes and RNA-DNA hybrid structures known as R-loops. Here, we review the detrimental impacts of transcription on genome stability in budding yeast, as well as the mitigating effects of transcription-coupled nucleotide excision repair and of systems that maintain DNA replication fork processivity and integrity. Interactions between DNA replication and transcription have particular potential to induce mutation and structural variation, but we conclude that such interactions must have only minor effects on DNA replication by the replisome with little if any direct mutagenic outcome. However, transcription can significantly impair the fidelity of replication fork rescue mechanisms, particularly Break Induced Replication, which is used to restart collapsed replication forks when other means fail. This leads to de novo mutations, structural variation and extrachromosomal circular DNA formation that contribute to genetic heterogeneity, but only under particular conditions and in particular genetic contexts, ensuring that the bulk of the genome remains extremely stable despite the seemingly frequent interactions between transcription and DNA replication.
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2
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Spector LP, Tiffany M, Ferraro NM, Abell NS, Montgomery SB, Kay MA. Evaluating the Genomic Parameters Governing rAAV-Mediated Homologous Recombination. Mol Ther 2021; 29:1028-1046. [PMID: 33248247 PMCID: PMC7934627 DOI: 10.1016/j.ymthe.2020.11.025] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2020] [Revised: 10/16/2020] [Accepted: 11/18/2020] [Indexed: 12/26/2022] Open
Abstract
Recombinant adeno-associated virus (rAAV) vectors have the unique ability to promote targeted integration of transgenes via homologous recombination at specified genomic sites, reaching frequencies of 0.1%-1%. We studied genomic parameters that influence targeting efficiencies on a large scale. To do this, we generated more than 1,000 engineered, doxycycline-inducible target sites in the human HAP1 cell line and infected this polyclonal population with a library of AAV-DJ targeting vectors, with each carrying a unique barcode. The heterogeneity of barcode integration at each target site provided an assessment of targeting efficiency at that locus. We compared targeting efficiency with and without target site transcription for identical chromosomal positions. Targeting efficiency was enhanced by target site transcription, while chromatin accessibility was associated with an increased likelihood of targeting. ChromHMM chromatin states characterizing transcription and enhancers in wild-type K562 cells were also associated with increased AAV-HR efficiency with and without target site transcription, respectively. Furthermore, the amenability of a site to targeting was influenced by the endogenous transcriptional level of intersecting genes. These results define important parameters that may not only assist in designing optimal targeting vectors for genome editing, but also provide new insights into the mechanism of AAV-mediated homologous recombination.
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Affiliation(s)
- Laura P Spector
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA
| | - Matthew Tiffany
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA; Department of Pediatrics, Stanford University School of Medicine, Stanford, CA, USA
| | - Nicole M Ferraro
- Biomedical Informatics Program, Stanford University School of Medicine, Stanford, CA, USA
| | - Nathan S Abell
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA
| | - Stephen B Montgomery
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA; Department of Pathology, Stanford University School of Medicine, Stanford, CA, USA
| | - Mark A Kay
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA; Department of Pediatrics, Stanford University School of Medicine, Stanford, CA, USA.
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3
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Tam AS, Sihota TS, Milbury KL, Zhang A, Mathew V, Stirling PC. Selective defects in gene expression control genome instability in yeast splicing mutants. Mol Biol Cell 2018; 30:191-200. [PMID: 30462576 PMCID: PMC6589566 DOI: 10.1091/mbc.e18-07-0439] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
RNA processing mutants have been broadly implicated in genome stability, but mechanistic links are often unclear. Two predominant models have emerged: one involving changes in gene expression that perturb other genome maintenance factors and another in which genotoxic DNA:RNA hybrids, called R-loops, impair DNA replication. Here we characterize genome instability phenotypes in yeast splicing factor mutants and find that mitotic defects, and in some cases R-loop accumulation, are causes of genome instability. In both cases, alterations in gene expression, rather than direct cis effects, are likely to contribute to instability. Genome instability in splicing mutants is exacerbated by loss of the spindle-assembly checkpoint protein Mad1. Moreover, removal of the intron from the α-tubulin gene TUB1 restores genome integrity. Thus, differing penetrance and selective effects on the transcriptome can lead to a range of phenotypes in conditional mutants of the spliceosome, including multiple routes to genome instability.
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Affiliation(s)
- Annie S Tam
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, BC V5Z 1L3, Canada.,Department of Medical Genetics, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Tianna S Sihota
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, BC V5Z 1L3, Canada
| | - Karissa L Milbury
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, BC V5Z 1L3, Canada
| | - Anni Zhang
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, BC V5Z 1L3, Canada
| | - Veena Mathew
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, BC V5Z 1L3, Canada
| | - Peter C Stirling
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, BC V5Z 1L3, Canada.,Department of Medical Genetics, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
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4
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Gadaleta MC, Noguchi E. Regulation of DNA Replication through Natural Impediments in the Eukaryotic Genome. Genes (Basel) 2017; 8:genes8030098. [PMID: 28272375 PMCID: PMC5368702 DOI: 10.3390/genes8030098] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2016] [Accepted: 03/03/2017] [Indexed: 02/07/2023] Open
Abstract
All living organisms need to duplicate their genetic information while protecting it from unwanted mutations, which can lead to genetic disorders and cancer development. Inaccuracies during DNA replication are the major cause of genomic instability, as replication forks are prone to stalling and collapse, resulting in DNA damage. The presence of exogenous DNA damaging agents as well as endogenous difficult-to-replicate DNA regions containing DNA–protein complexes, repetitive DNA, secondary DNA structures, or transcribing RNA polymerases, increases the risk of genomic instability and thus threatens cell survival. Therefore, understanding the cellular mechanisms required to preserve the genetic information during S phase is of paramount importance. In this review, we will discuss our current understanding of how cells cope with these natural impediments in order to prevent DNA damage and genomic instability during DNA replication.
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Affiliation(s)
- Mariana C Gadaleta
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA.
| | - Eishi Noguchi
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA.
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5
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Chumki SA, Dunn MK, Coates TF, Mishler JD, Younkin EM, Casper AM. Remarkably Long-Tract Gene Conversion Induced by Fragile Site Instability in Saccharomyces cerevisiae. Genetics 2016; 204:115-28. [PMID: 27343237 PMCID: PMC5012379 DOI: 10.1534/genetics.116.191205] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 06/23/2016] [Indexed: 01/29/2023] Open
Abstract
Replication stress causes breaks at chromosomal locations called common fragile sites. Deletions causing loss of heterozygosity (LOH) in human tumors are strongly correlated with common fragile sites, but the role of gene conversion in LOH at fragile sites in tumors is less well studied. Here, we investigated gene conversion stimulated by instability at fragile site FS2 in the yeast Saccharomyces cerevisiae In our screening system, mitotic LOH events near FS2 are identified by production of red/white sectored colonies. We analyzed single nucleotide polymorphisms between homologs to determine the cause and extent of LOH. Instability at FS2 increases gene conversion 48- to 62-fold, and conversions unassociated with crossover represent 6-7% of LOH events. Gene conversion can result from repair of mismatches in heteroduplex DNA during synthesis-dependent strand annealing (SDSA), double-strand break repair (DSBR), and from break-induced replication (BIR) that switches templates [double BIR (dBIR)]. It has been proposed that SDSA and DSBR typically result in shorter gene-conversion tracts than dBIR. In cells under replication stress, we found that bidirectional tracts at FS2 have a median length of 40.8 kb and a wide distribution of lengths; most of these tracts are not crossover-associated. Tracts that begin at the fragile site FS2 and extend only distally are significantly shorter. The high abundance and long length of noncrossover, bidirectional gene-conversion tracts suggests that dBIR is a prominent mechanism for repair of lesions at FS2, thus this mechanism is likely to be a driver of common fragile site-stimulated LOH in human tumors.
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Affiliation(s)
- Shahana A Chumki
- Department of Biology, Eastern Michigan University, Ypsilanti, Michigan 48197
| | - Mikael K Dunn
- Department of Biology, Eastern Michigan University, Ypsilanti, Michigan 48197
| | - Thomas F Coates
- Department of Biology, Eastern Michigan University, Ypsilanti, Michigan 48197
| | - Jeanmarie D Mishler
- Department of Biology, Eastern Michigan University, Ypsilanti, Michigan 48197
| | - Ellen M Younkin
- Department of Biology, Eastern Michigan University, Ypsilanti, Michigan 48197
| | - Anne M Casper
- Department of Biology, Eastern Michigan University, Ypsilanti, Michigan 48197
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6
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Affiliation(s)
- Hélène Gaillard
- Centro Andaluz de Biología Molecular y Medicina Regenerativa (CABIMER), Universidad de Sevilla, Sevilla 41092, Spain; ,
| | - Andrés Aguilera
- Centro Andaluz de Biología Molecular y Medicina Regenerativa (CABIMER), Universidad de Sevilla, Sevilla 41092, Spain; ,
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7
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Million-Weaver S, Samadpour AN, Moreno-Habel DA, Nugent P, Brittnacher MJ, Weiss E, Hayden HS, Miller SI, Liachko I, Merrikh H. An underlying mechanism for the increased mutagenesis of lagging-strand genes in Bacillus subtilis. Proc Natl Acad Sci U S A 2015; 112:E1096-105. [PMID: 25713353 PMCID: PMC4364195 DOI: 10.1073/pnas.1416651112] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We previously reported that lagging-strand genes accumulate mutations faster than those encoded on the leading strand in Bacillus subtilis. Although we proposed that orientation-specific encounters between replication and transcription underlie this phenomenon, the mechanism leading to the increased mutagenesis of lagging-strand genes remained unknown. Here, we report that the transcription-dependent and orientation-specific differences in mutation rates of genes require the B. subtilis Y-family polymerase, PolY1 (yqjH). We find that without PolY1, association of the replicative helicase, DnaC, and the recombination protein, RecA, with lagging-strand genes increases in a transcription-dependent manner. These data suggest that PolY1 promotes efficient replisome progression through lagging-strand genes, thereby reducing potentially detrimental breaks and single-stranded DNA at these loci. Y-family polymerases can alleviate potential obstacles to replisome progression by facilitating DNA lesion bypass, extension of D-loops, or excision repair. We find that the nucleotide excision repair (NER) proteins UvrA, UvrB, and UvrC, but not RecA, are required for transcription-dependent asymmetry in mutation rates of genes in the two orientations. Furthermore, we find that the transcription-coupling repair factor Mfd functions in the same pathway as PolY1 and is also required for increased mutagenesis of lagging-strand genes. Experimental and SNP analyses of B. subtilis genomes show mutational footprints consistent with these findings. We propose that the interplay between replication and transcription increases lesion susceptibility of, specifically, lagging-strand genes, activating an Mfd-dependent error-prone NER mechanism. We propose that this process, at least partially, underlies the accelerated evolution of lagging-strand genes.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Ivan Liachko
- Genome Sciences, University of Washington, Seattle, WA 98195
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8
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Deyle DR, Hansen RS, Cornea AM, Li LB, Burt AA, Alexander IE, Sandstrom RS, Stamatoyannopoulos JA, Wei CL, Russell DW. A genome-wide map of adeno-associated virus-mediated human gene targeting. Nat Struct Mol Biol 2014; 21:969-75. [PMID: 25282150 PMCID: PMC4405182 DOI: 10.1038/nsmb.2895] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 08/27/2014] [Indexed: 02/03/2023]
Abstract
To determine which genomic features promote homologous recombination, we created a genome-wide map of gene targeting sites. We used an adeno-associated virus vector to target identical loci introduced as transcriptionally active retroviral vectors. A comparison of ~2,000 targeted and untargeted sites showed that targeting occurred throughout the human genome and was not influenced by the presence of nearby CpG islands, sequence repeats or DNase I-hypersensitive sites. Targeted sites were preferentially located within transcription units, especially when the target loci were transcribed in the opposite orientation to their surrounding chromosomal genes. We determined the impact of DNA replication by mapping replication forks, which revealed a preference for recombination at target loci transcribed toward an incoming fork. Our results constitute the first genome-wide screen of gene targeting in mammalian cells and demonstrate a strong recombinogenic effect of colliding polymerases.
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Affiliation(s)
- David R Deyle
- Department of Medicine, University of Washington, Seattle, Washington, USA
| | - R Scott Hansen
- Department of Medicine, University of Washington, Seattle, Washington, USA
| | - Anda M Cornea
- Department of Molecular and Cellular Biology, University of Washington, Seattle, Washington, USA
| | - Li B Li
- Department of Medicine, University of Washington, Seattle, Washington, USA
| | - Amber A Burt
- Department of Medicine, University of Washington, Seattle, Washington, USA
| | - Ian E Alexander
- Gene Therapy Research Unit, Children's Medical Research Institute, Westmead, New South Wales, Australia
| | - Richard S Sandstrom
- Department of Genome Sciences, University of Washington, Seattle, Washington, USA
| | | | - Chia-Lin Wei
- Genomic Technologies Department, Joint Genome Institute, Walnut Creek, California, USA
| | - David W Russell
- 1] Department of Medicine, University of Washington, Seattle, Washington, USA. [2] Department of Biochemistry, University of Washington, Seattle, Washington, USA
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9
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Aguilera A, Gaillard H. Transcription and recombination: when RNA meets DNA. Cold Spring Harb Perspect Biol 2014; 6:6/8/a016543. [PMID: 25085910 DOI: 10.1101/cshperspect.a016543] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
A particularly relevant phenomenon in cell physiology and proliferation is the fact that spontaneous mitotic recombination is strongly enhanced by transcription. The most accepted view is that transcription increases the occurrence of double-strand breaks and/or single-stranded DNA gaps that are repaired by recombination. Most breaks would arise as a consequence of the impact that transcription has on replication fork progression, provoking its stalling and/or breakage. Here, we discuss the mechanisms responsible for the cross talk between transcription and recombination, with emphasis on (1) the transcription-replication conflicts as the main source of recombinogenic DNA breaks, and (2) the formation of cotranscriptional R-loops as a major cause of such breaks. The new emerging questions and perspectives are discussed on the basis of the interference between transcription and replication, as well as the way RNA influences genome dynamics.
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Affiliation(s)
- Andrés Aguilera
- Centro Andaluz de Biología Molecular y Medicina Regenerativa (CABIMER), Universidad de Sevilla, 41092 Seville, Spain
| | - Hélène Gaillard
- Centro Andaluz de Biología Molecular y Medicina Regenerativa (CABIMER), Universidad de Sevilla, 41092 Seville, Spain
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10
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The yeast and human FACT chromatin-reorganizing complexes solve R-loop-mediated transcription-replication conflicts. Genes Dev 2014; 28:735-48. [PMID: 24636987 PMCID: PMC4015491 DOI: 10.1101/gad.234070.113] [Citation(s) in RCA: 132] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The chromatin-reorganizing complex FACT functions in transcription elongation and DNA replication, yet its role in replication is not well understood. Here, Herrera-Moyano et al. find increased recombination rates and genetic instability in yeast mutants and FACT-depleted human cells. The results demonstrate a conserved function for FACT in the resolution of transcription–replication conflicts mediated by R loops. This study therefore links the roles of FACT in transcription elongation and DNA replication. FACT (facilitates chromatin transcription) is a chromatin-reorganizing complex that swaps nucleosomes around the RNA polymerase during transcription elongation and has a role in replication that is not fully understood yet. Here we show that recombination factors are required for the survival of yeast FACT mutants, consistent with an accumulation of DNA breaks that we detected by Rad52 foci and transcription-dependent hyperrecombination. Breaks also accumulate in FACT-depleted human cells, as shown by γH2AX foci and single-cell electrophoresis. Furthermore, FACT-deficient yeast and human cells show replication impairment, which in yeast we demonstrate by ChIP–chip (chromatin immunoprecipitation [ChIP] coupled with microarray analysis) of Rrm3 to occur genome-wide but preferentially at highly transcribed regions. Strikingly, in yeast FACT mutants, high levels of Rad52 foci are suppressed by RNH1 overexpression; R loops accumulate at high levels, and replication becomes normal when global RNA synthesis is inhibited in FACT-depleted human cells. The results demonstrate a key function of FACT in the resolution of R-loop-mediated transcription–replication conflicts, likely associated with a specific chromatin organization.
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11
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Gaillard H, Herrera-Moyano E, Aguilera A. Transcription-associated genome instability. Chem Rev 2013; 113:8638-61. [PMID: 23597121 DOI: 10.1021/cr400017y] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Hélène Gaillard
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla , Av. Américo Vespucio s/n, 41092 Seville, Spain
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12
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Steinacher R, Osman F, Dalgaard JZ, Lorenz A, Whitby MC. The DNA helicase Pfh1 promotes fork merging at replication termination sites to ensure genome stability. Genes Dev 2012; 26:594-602. [PMID: 22426535 DOI: 10.1101/gad.184663.111] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Bidirectionally moving DNA replication forks merge at termination sites composed of accidental or programmed DNA-protein barriers. If merging fails, then regions of unreplicated DNA can result in the breakage of DNA during mitosis, which in turn can give rise to genome instability. Despite its importance, little is known about the mechanisms that promote the final stages of fork merging in eukaryotes. Here we show that the Pif1 family DNA helicase Pfh1 plays a dual role in promoting replication fork termination. First, it facilitates replication past DNA-protein barriers, and second, it promotes the merging of replication forks. A failure of these processes in Pfh1-deficient cells results in aberrant chromosome segregation and heightened genome instability.
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Affiliation(s)
- Roland Steinacher
- Department of Biochemistry, University of Oxford, Oxford OX13QU, United Kingdom
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13
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Abstract
Alterations in genome sequence and structure contribute to somatic disease, affect the fitness of subsequent generations and drive evolutionary processes. The crucial roles of highly accurate replication and efficient repair in maintaining overall genome integrity are well-known, but the more localized stability costs that are associated with transcribing DNA into RNA molecules are less appreciated. Here we review the diverse ways in which the essential process of transcription alters the underlying DNA template and thereby modifies the genetic landscape.
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14
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Carr AM, Paek AL, Weinert T. DNA replication: failures and inverted fusions. Semin Cell Dev Biol 2011; 22:866-74. [PMID: 22020070 DOI: 10.1016/j.semcdb.2011.10.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Accepted: 10/12/2011] [Indexed: 11/16/2022]
Abstract
DNA replication normally follows the rules passed down from Watson and Crick: the chromosome duplicates as dictated by its antiparallel strands, base-pairing and leading and lagging strand differences. Real-life replication is more complicated, fraught with perils posed by chromosome damage for one, and by transcription of genes and by other perils that disrupt progress of the DNA replication machinery. Understanding the replication fork, including DNA structures, associated replisome and its regulators, is key to understanding how cells overcome perils and minimize error. Replication fork error leads to genome rearrangements and, potentially, cell death. Interest in the replication fork and its errors has recently gained added interest by the results of deep sequencing studies of human genomes. Several pathologies are associated with sometimes-bizarre genome rearrangements suggestive of elaborate replication fork failures. To try and understand the links between the replication fork, its failure and genome rearrangements, we discuss here phases of fork behavior (stall, collapse, restart and fork failures leading to rearrangements) and analyze two examples of instability from our own studies; one in fission yeast and the other in budding yeast.
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Affiliation(s)
- Antony M Carr
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton, Sussex, UK.
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15
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Wang J, Geesman GJ, Hostikka SL, Atallah M, Blackwell B, Lee E, Cook PJ, Pasaniuc B, Shariat G, Halperin E, Dobke M, Rosenfeld MG, Jordan IK, Lunyak VV. Inhibition of activated pericentromeric SINE/Alu repeat transcription in senescent human adult stem cells reinstates self-renewal. Cell Cycle 2011; 10:3016-30. [PMID: 21862875 PMCID: PMC3218602 DOI: 10.4161/cc.10.17.17543] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Accepted: 07/28/2011] [Indexed: 01/01/2023] Open
Abstract
Cellular aging is linked to deficiencies in efficient repair of DNA double strand breaks and authentic genome maintenance at the chromatin level. Aging poses a significant threat to adult stem cell function by triggering persistent DNA damage and ultimately cellular senescence. Senescence is often considered to be an irreversible process. Moreover, critical genomic regions engaged in persistent DNA damage accumulation are unknown. Here we report that 65% of naturally occurring repairable DNA damage in self-renewing adult stem cells occurs within transposable elements. Upregulation of Alu retrotransposon transcription upon ex vivo aging causes nuclear cytotoxicity associated with the formation of persistent DNA damage foci and loss of efficient DNA repair in pericentric chromatin. This occurs due to a failure to recruit of condensin I and cohesin complexes. Our results demonstrate that the cytotoxicity of induced Alu repeats is functionally relevant for the human adult stem cell aging. Stable suppression of Alu transcription can reverse the senescent phenotype, reinstating the cells' self-renewing properties and increasing their plasticity by altering so-called "master" pluripotency regulators.
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Affiliation(s)
- Jianrong Wang
- School of Biology, Georgia Institute of Technology, Atlanta, GA, USA
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16
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Gómez-González B, García-Rubio M, Bermejo R, Gaillard H, Shirahige K, Marín A, Foiani M, Aguilera A. Genome-wide function of THO/TREX in active genes prevents R-loop-dependent replication obstacles. EMBO J 2011; 30:3106-19. [PMID: 21701562 DOI: 10.1038/emboj.2011.206] [Citation(s) in RCA: 174] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Accepted: 05/25/2011] [Indexed: 11/09/2022] Open
Abstract
THO/TREX is a conserved nuclear complex that functions in mRNP biogenesis and prevents transcription-associated recombination. Whether or not it has a ubiquitous role in the genome is unknown. Chromatin immunoprecipitation (ChIP)-chip studies reveal that the Hpr1 component of THO and the Sub2 RNA-dependent ATPase have genome-wide distributions at active ORFs in yeast. In contrast to RNA polymerase II, evenly distributed from promoter to termination regions, THO and Sub2 are absent at promoters and distributed in a gradual 5' → 3' gradient. This is accompanied by a genome-wide impact of THO-Sub2 deletions on expression of highly expressed, long and high G+C-content genes. Importantly, ChIP-chips reveal an over-recruitment of Rrm3 in active genes in THO mutants that is reduced by RNaseH1 overexpression. Our work establishes a genome-wide function for THO-Sub2 in transcription elongation and mRNP biogenesis that function to prevent the accumulation of transcription-mediated replication obstacles, including R-loops.
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Affiliation(s)
- Belén Gómez-González
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC, Sevilla, Spain
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17
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Sofueva S, Osman F, Lorenz A, Steinacher R, Castagnetti S, Ledesma J, Whitby MC. Ultrafine anaphase bridges, broken DNA and illegitimate recombination induced by a replication fork barrier. Nucleic Acids Res 2011; 39:6568-84. [PMID: 21576223 PMCID: PMC3159475 DOI: 10.1093/nar/gkr340] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Most DNA double-strand breaks (DSBs) in S- and G2-phase cells are repaired accurately by Rad51-dependent sister chromatid recombination. However, a minority give rise to gross chromosome rearrangements (GCRs), which can result in disease/death. What determines whether a DSB is repaired accurately or inaccurately is currently unclear. We provide evidence that suggests that perturbing replication by a non-programmed protein-DNA replication fork barrier results in the persistence of replication intermediates (most likely regions of unreplicated DNA) into mitosis, which results in anaphase bridge formation and ultimately to DNA breakage. However, unlike previously characterised replication-associated DSBs, these breaks are repaired mainly by Rad51-independent processes such as single-strand annealing, and are therefore prone to generate GCRs. These data highlight how a replication-associated DSB can be predisposed to give rise to genome rearrangements in eukaryotes.
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Affiliation(s)
- Sevil Sofueva
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
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18
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Clelland BW, Schultz MC. Genome stability control by checkpoint regulation of tRNA gene transcription. Transcription 2010; 1:115-125. [PMID: 21326884 DOI: 10.4161/trns.1.3.13735] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Revised: 08/31/2010] [Accepted: 09/23/2010] [Indexed: 12/21/2022] Open
Abstract
The RNA polymerase III pre-initiation complex (PIC) assembled on yeast tRNA genes naturally causes replication fork pausing that contributes to genome instability. Mechanistic coupling of the fork pausing activity of tRNA genes to replication has long been considered likely, but only recently demonstrated. In contrast to the expectation that this coupling might occur by a passive mechanism such as direct disruption of transcription factor-DNA complexes by a component of the replisome, it turns out that disassembly of the RNA polymerase III PIC is actively controlled by the replication stress checkpoint signal transduction pathway. This advance supports a new model in which checkpoint-dependent disassembly of the transcription machinery at tRNA genes is a vital component of an overall system of genome stability control that also targets replication and DNA repair proteins.
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Affiliation(s)
- Brett W Clelland
- Department of Biochemistry; School of Molecular and Systems Medicine; University of Alberta; Edmonton, AB Canada
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Replication stress checkpoint signaling controls tRNA gene transcription. Nat Struct Mol Biol 2010; 17:976-81. [DOI: 10.1038/nsmb.1857] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2010] [Accepted: 05/20/2010] [Indexed: 01/21/2023]
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A role for recombination in centromere function. Trends Genet 2010; 26:209-13. [PMID: 20382440 DOI: 10.1016/j.tig.2010.02.005] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2010] [Revised: 02/22/2010] [Accepted: 02/24/2010] [Indexed: 11/20/2022]
Abstract
Centromeres are essential for chromosome segregation during both mitosis and meiosis. There are no obvious or conserved DNA sequence motif determinants for centromere function, but the complex centromeres found in the majority of eukaryotes studied to date consist of repetitive DNA sequences. A striking feature of these repeats is that they maintain a high level of inter-repeat sequence identity within the centromere. This observation is suggestive of a recombination mechanism that operates at centromeres. Here we postulate that inter-repeat homologous recombination plays an intrinsic role in centromere function by forming covalently closed DNA loops. Moreover, the model provides an explanation of why both inverted and direct repeats are maintained and how they contribute to centromere function.
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