1
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Siler J, Guo N, Liu Z, Qin Y, Bi X. γH2A/γH2AX Mediates DNA Damage-Specific Control of Checkpoint Signaling in Saccharomyces cerevisiae. Int J Mol Sci 2024; 25:2462. [PMID: 38473708 DOI: 10.3390/ijms25052462] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2024] [Revised: 02/13/2024] [Accepted: 02/16/2024] [Indexed: 03/14/2024] Open
Abstract
DNA lesions trigger DNA damage checkpoint (DDC) signaling which arrests cell cycle progression and promotes DNA damage repair. In Saccharomyces cerevisiae, phosphorylation of histone H2A (γH2A, equivalent to γH2AX in mammals) is an early chromatin mark induced by DNA damage that is recognized by a group of DDC and DNA repair factors. We find that γH2A negatively regulates the G2/M checkpoint in response to the genotoxin camptothecin, which is a DNA topoisomerase I poison. γH2A also suppresses DDC signaling induced by the DNA alkylating agent methyl methanesulfonate. These results differ from prior findings, which demonstrate positive or no roles of γH2A in DDC in response to other DNA damaging agents such as phleomycin and ionizing radiation, which suggest that γH2A has DNA damage-specific effects on DDC signaling. We also find evidence supporting the notion that γH2A regulates DDC signaling by mediating the competitive recruitment of the DDC mediator Rad9 and the DNA repair factor Rtt107 to DNA lesions. We propose that γH2A/γH2AX serves to create a dynamic balance between DDC and DNA repair that is influenced by the nature of DNA damage.
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Affiliation(s)
- Jasmine Siler
- Department of Biology, University of Rochester, Rochester, NY 14627, USA
| | - Na Guo
- Department of Biology, University of Rochester, Rochester, NY 14627, USA
- College of Food Science and Engineering, Jilin University, Changchun 130012, China
| | - Zhengfeng Liu
- Department of Biology, University of Rochester, Rochester, NY 14627, USA
| | - Yuhua Qin
- Department of Biology, University of Rochester, Rochester, NY 14627, USA
| | - Xin Bi
- Department of Biology, University of Rochester, Rochester, NY 14627, USA
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2
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Fun30 and Rtt109 Mediate Epigenetic Regulation of the DNA Damage Response Pathway in C. albicans. J Fungi (Basel) 2022; 8:jof8060559. [PMID: 35736042 PMCID: PMC9225650 DOI: 10.3390/jof8060559] [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: 03/17/2022] [Revised: 03/27/2022] [Accepted: 03/29/2022] [Indexed: 01/27/2023] Open
Abstract
Fun30, an ATP-dependent chromatin remodeler from S. cerevisiae, is known to mediate both regulation of gene expression as well as DNA damage response/repair. The Fun30 from C. albicans has not yet been elucidated. We show that C. albicans Fun30 is functionally homologous to both S. cerevisiae Fun30 and human SMARCAD1. Further, C. albicans Fun30 can mediate double-strand break end resection as well as regulate gene expression. This protein regulates transcription of RTT109, TEL1, MEC1, and SNF2-genes that encode for proteins involved in DNA damage response and repair pathways. The regulation mediated by C. albicans Fun30 is dependent on its ATPase activity. The expression of FUN30, in turn, is regulated by histone H3K56 acetylation catalyzed by Rtt109 and encoded by RTT109. The RTT109Hz/FUN30Hz mutant strain shows sensitivity to oxidative stress and resistance to MMS as compared to the wild-type strain. Quantitative PCR showed that the sensitivity to oxidative stress results from downregulation of MEC1, RAD9, MRC1, and RAD5 expression; ChIP experiments showed that Fun30 but not H3K56ac regulates the expression of these genes in response to oxidative stress. In contrast, upon treatment with MMS, the expression of RAD9 is upregulated, which is modulated by both Fun30 and H3K56 acetylation. Thus, Fun30 and H3K56 acetylation mediate the response to genotoxic agents in C. albicans by regulating the expression of DNA damage response and repair pathway genes.
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3
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Kang H, Liu Y, Fan T, Ma J, Wu D, Heitz T, Shen WH, Zhu Y. Arabidopsis CHROMATIN REMODELING 19 acts as a transcriptional repressor and contributes to plant pathogen resistance. THE PLANT CELL 2022; 34:1100-1116. [PMID: 34954802 PMCID: PMC8894922 DOI: 10.1093/plcell/koab318] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 12/21/2021] [Indexed: 06/14/2023]
Abstract
Chromatin remodelers act in an ATP-dependent manner to modulate chromatin structure and thus genome function. Here, we report that the Arabidopsis (Arabidopsis thaliana) remodeler CHROMATIN REMODELING19 (CHR19) is enriched in gene body regions, and its depletion causes massive changes in nucleosome position and occupancy in the genome. Consistent with these changes, an in vitro assay verified that CHR19 can utilize ATP to slide nucleosomes. A variety of inducible genes, including several important genes in the salicylic acid (SA) and jasmonic acid (JA) pathways, were transcriptionally upregulated in the chr19 mutant under normal growth conditions, indicative of a role of CHR19 in transcriptional repression. In addition, the chr19 mutation triggered higher susceptibility to the JA pathway-defended necrotrophic fungal pathogen Botrytis cinerea, but did not affect the growth of the SA pathway-defended hemibiotrophic bacterial pathogen Pseudomonas syringae pv. tomato DC3000. Expression of CHR19 was tissue-specific and inhibited specifically by SA treatment. Such inhibition significantly decreased the local chromatin enrichment of CHR19 at the associated SA pathway genes, which resulted in their full activation upon SA treatment. Overall, our findings clarify CHR19 to be a novel regulator acting at the chromatin level to impact the transcription of genes underlying plant resistance to different pathogens.
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Affiliation(s)
- Huijia Kang
- Department of Biochemistry, Institute of Plant Biology, School of Life
Sciences, State Key Laboratory of Genetic Engineering, Collaborative Innovation Center for
Genetics and Development, Fudan University, Shanghai 200438, China
- Institut de Biologie Moléculaire des Plantes, CNRS, Université de
Strasbourg, Strasbourg Cedex 67084, France
| | - Yuhao Liu
- National Cancer Center/National Clinical Research Center for Cancer/Cancer
Hospital & Shenzhen Hospital, Chinese Academy of Medical Sciences and Peking Union
Medical College, Shenzhen 518116, China; Chinese
Academy of Medical Sciences and Peking Union Medical College, Beijing, 100021,
China
| | - Tianyi Fan
- Department of Biochemistry, Institute of Plant Biology, School of Life
Sciences, State Key Laboratory of Genetic Engineering, Collaborative Innovation Center for
Genetics and Development, Fudan University, Shanghai 200438, China
| | - Jing Ma
- Department of Biochemistry, Institute of Plant Biology, School of Life
Sciences, State Key Laboratory of Genetic Engineering, Collaborative Innovation Center for
Genetics and Development, Fudan University, Shanghai 200438, China
| | - Di Wu
- Department of Biochemistry, Institute of Plant Biology, School of Life
Sciences, State Key Laboratory of Genetic Engineering, Collaborative Innovation Center for
Genetics and Development, Fudan University, Shanghai 200438, China
| | - Thierry Heitz
- Institut de Biologie Moléculaire des Plantes, CNRS, Université de
Strasbourg, Strasbourg Cedex 67084, France
| | - Wen-Hui Shen
- Institut de Biologie Moléculaire des Plantes, CNRS, Université de
Strasbourg, Strasbourg Cedex 67084, France
| | - Yan Zhu
- Department of Biochemistry, Institute of Plant Biology, School of Life
Sciences, State Key Laboratory of Genetic Engineering, Collaborative Innovation Center for
Genetics and Development, Fudan University, Shanghai 200438, China
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4
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Wu PS, Grosser J, Cameron DP, Baranello L, Ström L. Deficiency of Polη in Saccharomyces cerevisiae reveals the impact of transcription on damage-induced cohesion. PLoS Genet 2021; 17:e1009763. [PMID: 34499654 PMCID: PMC8454932 DOI: 10.1371/journal.pgen.1009763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 09/21/2021] [Accepted: 08/05/2021] [Indexed: 11/18/2022] Open
Abstract
The structural maintenance of chromosome (SMC) complex cohesin mediates sister chromatid cohesion established during replication, and damage-induced cohesion formed in response to DSBs post-replication. The translesion synthesis polymerase Polη is required for damage-induced cohesion through a hitherto unknown mechanism. Since Polη is functionally associated with transcription, and transcription triggers de novo cohesion in Schizosaccharomyces pombe, we hypothesized that transcription facilitates damage-induced cohesion in Saccharomyces cerevisiae. Here, we show dysregulated transcriptional profiles in the Polη null mutant (rad30Δ), where genes involved in chromatin assembly and positive transcription regulation were downregulated. In addition, chromatin association of RNA polymerase II was reduced at promoters and coding regions in rad30Δ compared to WT cells, while occupancy of the H2A.Z variant (Htz1) at promoters was increased in rad30Δ cells. Perturbing histone exchange at promoters inactivated damage-induced cohesion, similarly to deletion of the RAD30 gene. Conversely, altering regulation of transcription elongation suppressed the deficient damage-induced cohesion in rad30Δ cells. Furthermore, transcription inhibition negatively affected formation of damage-induced cohesion. These results indicate that the transcriptional deregulation of the Polη null mutant is connected with its reduced capacity to establish damage-induced cohesion. This also suggests a linkage between regulation of transcription and formation of damage-induced cohesion after replication.
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Affiliation(s)
- Pei-Shang Wu
- Karolinska Institutet, Department of Cell and Molecular Biology, Stockholm, Sweden
| | - Jan Grosser
- Karolinska Institutet, Department of Cell and Molecular Biology, Stockholm, Sweden
| | - Donald P. Cameron
- Karolinska Institutet, Department of Cell and Molecular Biology, Stockholm, Sweden
| | - Laura Baranello
- Karolinska Institutet, Department of Cell and Molecular Biology, Stockholm, Sweden
| | - Lena Ström
- Karolinska Institutet, Department of Cell and Molecular Biology, Stockholm, Sweden
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5
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Al-Natour Z, Chalissery J, Hassan AH. Fun30 chromatin remodeler helps in dealing with torsional stress and camptothecin-induced DNA damage. Yeast 2020; 38:170-182. [PMID: 33141948 DOI: 10.1002/yea.3534] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2020] [Revised: 10/04/2020] [Accepted: 10/26/2020] [Indexed: 12/19/2022] Open
Abstract
Fun30 is an ATP-dependent chromatin remodeler in budding yeast that is involved in cellular processes important for maintaining genomic stability such as gene silencing and DNA damage repair. Cells lacking Fun30 are moderately sensitive to the topoisomerase inhibitor camptothecin and exhibit a delay in cell cycle progression in the presence of camptothecin. Here, we show that Fun30 is required to cope with torsional stress in the absence of Top1. Moreover, we show through genetic studies that Fun30 acts in a parallel pathway to Mus81 endonuclease but is epistatic to Tdp1 phosphodiesterase and Rad1 endonuclease in the repair of camptothecin-induced DNA damage. More importantly, we show that DNA damage sensitivity of Fun30 deficient cells is enhanced in the absence of RNase H enzymes that remove RNA:DNA hybrids. We believe that chromatin remodeling by Fun30 may be important in dealing with torsional stress and camptothecin-induced DNA damage.
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Affiliation(s)
- Zeina Al-Natour
- Department of Biochemistry, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Jisha Chalissery
- Department of Biochemistry, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Ahmed H Hassan
- Department of Biochemistry, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
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6
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Niu Q, Wang W, Wei Z, Byeon B, Das AB, Chen BS, Wu WH. Role of the ATP-dependent chromatin remodeling enzyme Fun30/Smarcad1 in the regulation of mRNA splicing. Biochem Biophys Res Commun 2020; 526:453-458. [PMID: 32234239 DOI: 10.1016/j.bbrc.2020.02.175] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Accepted: 02/26/2020] [Indexed: 10/24/2022]
Abstract
The yeast ATP-dependent chromatin remodeling enzyme Fun30 has been shown to regulate heterochromatin silencing, DNA repair, transcription, and chromatin organization. Although chromatin structure has been proposed to influence splice site recognition and regulation, whether ATP-dependent chromatin remodeling enzyme plays a role in regulating splicing is not known. In this study, we find that pre-mRNA splicing efficiency is impaired and the recruitment of spliceosome is compromised in Fun30-depleted cells. In addition, Fun30 is enriched in the gene body of individual intron-containing genes. Moreover, we show that pre-mRNA splicing efficiency is dependent on the chromatin remodeling activity of Fun30. The function of Fun30 in splicing is further supported by the observation that, Smarcad1, the mammalian homolog of Fun30, regulates alternative splicing. Taken together, these results provide evidence for a novel role of Fun30 in regulating splicing.
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Affiliation(s)
- Qiankun Niu
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA, 30912, USA
| | - Wei Wang
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA, 30912, USA
| | - Zhe Wei
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA, 30912, USA
| | - Boseon Byeon
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA, 30912, USA
| | - Asim Bikas Das
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA, 30912, USA
| | - Bo-Shiun Chen
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA, 30912, USA; Department of Neurology, Medical College of Georgia, Augusta University, Augusta, GA, 30912, USA; Research Center for Emerging Viral Infections, College of Medicine, Chang Gung University, Taoyuan, 33302, Taiwan ROC
| | - Wei-Hua Wu
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA, 30912, USA; Department of Neurology, Medical College of Georgia, Augusta University, Augusta, GA, 30912, USA.
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7
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Ait-Saada A, Khorosjutina O, Chen J, Kramarz K, Maksimov V, Svensson JP, Lambert S, Ekwall K. Chromatin remodeler Fft3 plays a dual role at blocked DNA replication forks. Life Sci Alliance 2019; 2:e201900433. [PMID: 31575705 PMCID: PMC6771652 DOI: 10.26508/lsa.201900433] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Revised: 09/23/2019] [Accepted: 09/24/2019] [Indexed: 01/26/2023] Open
Abstract
Here, we investigate the function of fission yeast Fun30/Smarcad1 family of SNF2 ATPase-dependent chromatin remodeling enzymes in DNA damage repair. There are three Fun30 homologues in fission yeast, Fft1, Fft2, and Fft3. We find that only Fft3 has a function in DNA repair and it is needed for single-strand annealing of an induced double-strand break. Furthermore, we use an inducible replication fork barrier system to show that Fft3 has two distinct roles at blocked DNA replication forks. First, Fft3 is needed for the resection of nascent strands, and second, it is required to restart the blocked forks. The latter function is independent of its ATPase activity.
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Affiliation(s)
- Anissia Ait-Saada
- Institut Curie, Paris-Saclay University, Centre National de la Recherche Scientifique, Unités Mixtes de Recherche 3348, F-91405, Orsay, France
| | - Olga Khorosjutina
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden
| | - Jiang Chen
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden
| | - Karol Kramarz
- Institut Curie, Paris-Saclay University, Centre National de la Recherche Scientifique, Unités Mixtes de Recherche 3348, F-91405, Orsay, France
| | - Vladimir Maksimov
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden
| | - J Peter Svensson
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden
| | - Sarah Lambert
- Institut Curie, Paris-Saclay University, Centre National de la Recherche Scientifique, Unités Mixtes de Recherche 3348, F-91405, Orsay, France
| | - Karl Ekwall
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden
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8
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Gallo D, Kim T, Szakal B, Saayman X, Narula A, Park Y, Branzei D, Zhang Z, Brown GW. Rad5 Recruits Error-Prone DNA Polymerases for Mutagenic Repair of ssDNA Gaps on Undamaged Templates. Mol Cell 2019; 73:900-914.e9. [PMID: 30733119 DOI: 10.1016/j.molcel.2019.01.001] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2018] [Revised: 09/13/2018] [Accepted: 12/27/2018] [Indexed: 12/30/2022]
Abstract
Post-replication repair (PRR) allows tolerance of chemical- and UV-induced DNA base lesions in both an error-free and an error-prone manner. In classical PRR, PCNA monoubiquitination recruits translesion synthesis (TLS) DNA polymerases that can replicate through lesions. We find that PRR responds to DNA replication stress that does not cause base lesions. Rad5 forms nuclear foci during normal S phase and after exposure to types of replication stress where DNA base lesions are likely absent. Rad5 binds to the sites of stressed DNA replication forks, where it recruits TLS polymerases to repair single-stranded DNA (ssDNA) gaps, preventing mitotic defects and chromosome breaks. In contrast to the prevailing view of PRR, our data indicate that Rad5 promotes both mutagenic and error-free repair of undamaged ssDNA that arises during physiological and exogenous replication stress.
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Affiliation(s)
- David Gallo
- Department of Biochemistry, University of Toronto, 1 King's College Circle, Toronto, ON M5S 3E1, Canada; Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON M5S 3E1, Canada
| | - TaeHyung Kim
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON M5S 3E1, Canada; Department of Computer Science, University of Toronto, 1 King's College Circle, Toronto, ON M5S 3E1, Canada
| | - Barnabas Szakal
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, Via Adamello 16, 20139 Milan, Italy
| | - Xanita Saayman
- Department of Biochemistry, University of Toronto, 1 King's College Circle, Toronto, ON M5S 3E1, Canada; Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON M5S 3E1, Canada
| | - Ashrut Narula
- Department of Biochemistry, University of Toronto, 1 King's College Circle, Toronto, ON M5S 3E1, Canada; Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON M5S 3E1, Canada
| | - Yoona Park
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON M5S 3E1, Canada; Department of Computer Science, University of Toronto, 1 King's College Circle, Toronto, ON M5S 3E1, Canada
| | - Dana Branzei
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, Via Adamello 16, 20139 Milan, Italy; Istituto di Genetica Molecolare, Consiglio Nazionale delle Ricerche (IGM-CNR), Via Abbiategrasso 207, 27100 Pavia, Italy
| | - Zhaolei Zhang
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON M5S 3E1, Canada; Department of Computer Science, University of Toronto, 1 King's College Circle, Toronto, ON M5S 3E1, Canada
| | - Grant W Brown
- Department of Biochemistry, University of Toronto, 1 King's College Circle, Toronto, ON M5S 3E1, Canada; Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, ON M5S 3E1, Canada.
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Prado F. Homologous Recombination: To Fork and Beyond. Genes (Basel) 2018; 9:genes9120603. [PMID: 30518053 PMCID: PMC6316604 DOI: 10.3390/genes9120603] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Revised: 11/29/2018] [Accepted: 11/29/2018] [Indexed: 12/15/2022] Open
Abstract
Accurate completion of genome duplication is threatened by multiple factors that hamper the advance and stability of the replication forks. Cells need to tolerate many of these blocking lesions to timely complete DNA replication, postponing their repair for later. This process of lesion bypass during DNA damage tolerance can lead to the accumulation of single-strand DNA (ssDNA) fragments behind the fork, which have to be filled in before chromosome segregation. Homologous recombination plays essential roles both at and behind the fork, through fork protection/lesion bypass and post-replicative ssDNA filling processes, respectively. I review here our current knowledge about the recombination mechanisms that operate at and behind the fork in eukaryotes, and how these mechanisms are controlled to prevent unscheduled and toxic recombination intermediates. A unifying model to integrate these mechanisms in a dynamic, replication fork-associated process is proposed from yeast results.
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Affiliation(s)
- Félix Prado
- Department of Genome Biology, Andalusian Molecular Biology and Regenerative Medicine Center (CABIMER), CSIC-University of Seville-University Pablo de Olavide, 41092 Seville, Spain.
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10
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Siler J, Xia B, Wong C, Kath M, Bi X. Cell cycle-dependent positive and negative functions of Fun30 chromatin remodeler in DNA damage response. DNA Repair (Amst) 2017; 50:61-70. [PMID: 28089177 DOI: 10.1016/j.dnarep.2016.12.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Revised: 12/03/2016] [Accepted: 12/31/2016] [Indexed: 11/17/2022]
Abstract
The evolutionally conserved Fun30 chromatin remodeler in Saccharomyces cerevisiae has been shown to contribute to cellular resistance to genotoxic stress inflicted by camptothecin (CPT), methyl methanesulfonate (MMS) and hydroxyurea (HU). Fun30 aids in extensive DNA resection of DNA double stranded break (DSB) ends, which is thought to underlie its role in CPT-resistance. How Fun30 promotes MMS- or HU-resistance has not been resolved. Interestingly, we have recently found Fun30 to also play a negative role in cellular tolerance to MMS and HU in the absence of the Rad5-dependent DNA damage tolerance pathway. In this report, we show that Fun30 acts to down regulate Rad9-dependent DNA damage checkpoint triggered by CPT or MMS, but does not affect Rad9-independent intra-S phase replication checkpoint induced by MMS or HU. These results support the notion that Fun30 contributes to cellular response to DSBs by preventing excessive DNA damage checkpoint activation in addition to its role in facilitating DNA end resection. On the other hand, we present evidence suggesting that Fun30's negative function in MMS- and HU-tolerance in the absence of Rad5 is not related to its regulation of checkpoint activity. Moreover, we find Fun30 to be cell cycle regulated with its abundance peaking in G2/M phase of the cell cycle. Importantly, we demonstrate that artificially restricting Fun30 expression to G2/M does not affect its positive or negative function in genotoxin-resistance, but confining Fun30 to S phase abolishes its functions. These results indicate that both positive and negative functions of Fun30 in DNA damage response occur mainly in G2/M phase.
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Affiliation(s)
- Jasmine Siler
- Department of Biology, University of Rochester, Rochester, NY 14627, USA
| | - Bowen Xia
- Department of Biology, University of Rochester, Rochester, NY 14627, USA
| | - Carina Wong
- Department of Biology, University of Rochester, Rochester, NY 14627, USA
| | - Morgan Kath
- Department of Biology, University of Rochester, Rochester, NY 14627, USA
| | - Xin Bi
- Department of Biology, University of Rochester, Rochester, NY 14627, USA.
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Abstract
DNA damage may compromise genome integrity and lead to cell death. Cells have evolved a variety of processes to respond to DNA damage including damage repair and tolerance mechanisms, as well as damage checkpoints. The DNA damage tolerance (DDT) pathway promotes the bypass of single-stranded DNA lesions encountered by DNA polymerases during DNA replication. This prevents the stalling of DNA replication. Two mechanistically distinct DDT branches have been characterized. One is translesion synthesis (TLS) in which a replicative DNA polymerase is temporarily replaced by a specialized TLS polymerase that has the ability to replicate across DNA lesions. TLS is mechanistically simple and straightforward, but it is intrinsically error-prone. The other is the error-free template switching (TS) mechanism in which the stalled nascent strand switches from the damaged template to the undamaged newly synthesized sister strand for extension past the lesion. Error-free TS is a complex but preferable process for bypassing DNA lesions. However, our current understanding of this pathway is sketchy. An increasing number of factors are being found to participate or regulate this important mechanism, which is the focus of this editorial.
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