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Zamarreño J, Muñoz S, Alonso-Rodríguez E, Alcalá M, Rodríguez S, Bermejo R, Sacristán MP, Bueno A. Timely lagging strand maturation relies on Ubp10 deubiquitylase-mediated PCNA dissociation from replicating chromatin. Nat Commun 2024; 15:8183. [PMID: 39294185 PMCID: PMC11411133 DOI: 10.1038/s41467-024-52542-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Accepted: 09/11/2024] [Indexed: 09/20/2024] Open
Abstract
Synthesis and maturation of Okazaki Fragments is an incessant and highly efficient metabolic process completing the synthesis of the lagging strands at replication forks during S phase. Accurate Okazaki fragment maturation (OFM) is crucial to maintain genome integrity and, therefore, cell survival in all living organisms. In eukaryotes, OFM involves the consecutive action of DNA polymerase Pol ∂, 5' Flap endonuclease Fen1 and DNA ligase I, and constitutes the best example of a sequential process coordinated by the sliding clamp PCNA. For OFM to occur efficiently, cooperation of these enzymes with PCNA must be highly regulated. Here, we present evidence of a role for the K164-PCNA-deubiquitylase Ubp10 in the maturation of Okazaki fragments in the budding yeast Saccharomyces cerevisiae. We show that Ubp10 associates with lagging-strand DNA synthesis machineries on replicating chromatin to ensure timely ligation of Okazaki fragments by promoting PCNA dissociation from chromatin requiring lysine 164 deubiquitylation.
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Affiliation(s)
- Javier Zamarreño
- Instituto de Biología Molecular y Celular del Cáncer (IBMCC), Universidad de Salamanca-CSIC, Campus Miguel de Unamuno, Salamanca, Spain
- Departamento de Microbiología y Genética, Universidad de Salamanca, Campus Miguel de Unamuno, Salamanca, Spain
| | - Sofía Muñoz
- Instituto de Biología Molecular y Celular del Cáncer (IBMCC), Universidad de Salamanca-CSIC, Campus Miguel de Unamuno, Salamanca, Spain
- Departamento de Microbiología y Genética, Universidad de Salamanca, Campus Miguel de Unamuno, Salamanca, Spain
- Instituto de Biología Funcional y Genómica (IBFG), CSIC-Universidad de Salamanca, Salamanca, Spain
| | - Esmeralda Alonso-Rodríguez
- Instituto de Biología Molecular y Celular del Cáncer (IBMCC), Universidad de Salamanca-CSIC, Campus Miguel de Unamuno, Salamanca, Spain
- Departamento de Microbiología y Genética, Universidad de Salamanca, Campus Miguel de Unamuno, Salamanca, Spain
| | - Macarena Alcalá
- Instituto de Biología Molecular y Celular del Cáncer (IBMCC), Universidad de Salamanca-CSIC, Campus Miguel de Unamuno, Salamanca, Spain
- Departamento de Microbiología y Genética, Universidad de Salamanca, Campus Miguel de Unamuno, Salamanca, Spain
| | - Sergio Rodríguez
- Instituto de Biología Molecular y Celular del Cáncer (IBMCC), Universidad de Salamanca-CSIC, Campus Miguel de Unamuno, Salamanca, Spain
- Departamento de Microbiología y Genética, Universidad de Salamanca, Campus Miguel de Unamuno, Salamanca, Spain
| | - Rodrigo Bermejo
- Centro de Investigaciones Biológicas "Margarita Salas", CSIC, Madrid, Spain
| | - María P Sacristán
- Instituto de Biología Molecular y Celular del Cáncer (IBMCC), Universidad de Salamanca-CSIC, Campus Miguel de Unamuno, Salamanca, Spain.
- Departamento de Microbiología y Genética, Universidad de Salamanca, Campus Miguel de Unamuno, Salamanca, Spain.
| | - Avelino Bueno
- Instituto de Biología Molecular y Celular del Cáncer (IBMCC), Universidad de Salamanca-CSIC, Campus Miguel de Unamuno, Salamanca, Spain.
- Departamento de Microbiología y Genética, Universidad de Salamanca, Campus Miguel de Unamuno, Salamanca, Spain.
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2
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Polo Rivera C, Deegan TD, Labib KPM. CMG helicase disassembly is essential and driven by two pathways in budding yeast. EMBO J 2024; 43:3818-3845. [PMID: 39039287 PMCID: PMC11405719 DOI: 10.1038/s44318-024-00161-x] [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: 03/24/2024] [Revised: 06/12/2024] [Accepted: 06/19/2024] [Indexed: 07/24/2024] Open
Abstract
The CMG helicase is the stable core of the eukaryotic replisome and is ubiquitylated and disassembled during DNA replication termination. Fungi and animals use different enzymes to ubiquitylate the Mcm7 subunit of CMG, suggesting that CMG ubiquitylation arose repeatedly during eukaryotic evolution. Until now, it was unclear whether cells also have ubiquitin-independent pathways for helicase disassembly and whether CMG disassembly is essential for cell viability. Using reconstituted assays with budding yeast CMG, we generated the mcm7-10R allele that compromises ubiquitylation by SCFDia2. mcm7-10R delays helicase disassembly in vivo, driving genome instability in the next cell cycle. These data indicate that defective CMG ubiquitylation explains the major phenotypes of cells lacking Dia2. Notably, the viability of mcm7-10R and dia2∆ is dependent upon the related Rrm3 and Pif1 DNA helicases that have orthologues in all eukaryotes. We show that Rrm3 acts during S-phase to disassemble old CMG complexes from the previous cell cycle. These findings indicate that CMG disassembly is essential in yeast cells and suggest that Pif1-family helicases might have mediated CMG disassembly in ancestral eukaryotes.
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Affiliation(s)
- Cristian Polo Rivera
- MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
| | - Tom D Deegan
- MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK.
- MRC Human Genetics Unit, Institute of Genetics and Cancer, University of Edinburgh, Edinburgh, EH4 2XU, UK.
| | - Karim P M Labib
- MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK.
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3
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Medina-Rivera M, Phelps S, Sridharan M, Becker J, Lamb N, Kumar C, Sutton M, Bielinsky A, Balakrishnan L, Surtees J. Elevated MSH2 MSH3 expression interferes with DNA metabolism in vivo. Nucleic Acids Res 2023; 51:12185-12206. [PMID: 37930834 PMCID: PMC10711559 DOI: 10.1093/nar/gkad934] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 09/30/2023] [Accepted: 10/10/2023] [Indexed: 11/08/2023] Open
Abstract
The Msh2-Msh3 mismatch repair (MMR) complex in Saccharomyces cerevisiae recognizes and directs repair of insertion/deletion loops (IDLs) up to ∼17 nucleotides. Msh2-Msh3 also recognizes and binds distinct looped and branched DNA structures with varying affinities, thereby contributing to genome stability outside post-replicative MMR through homologous recombination, double-strand break repair (DSBR) and the DNA damage response. In contrast, Msh2-Msh3 promotes genome instability through trinucleotide repeat (TNR) expansions, presumably by binding structures that form from single-stranded (ss) TNR sequences. We previously demonstrated that Msh2-Msh3 binding to 5' ssDNA flap structures interfered with Rad27 (Fen1 in humans)-mediated Okazaki fragment maturation (OFM) in vitro. Here we demonstrate that elevated Msh2-Msh3 levels interfere with DNA replication and base excision repair in vivo. Elevated Msh2-Msh3 also induced a cell cycle arrest that was dependent on RAD9 and ELG1 and led to PCNA modification. These phenotypes also required Msh2-Msh3 ATPase activity and downstream MMR proteins, indicating an active mechanism that is not simply a result of Msh2-Msh3 DNA-binding activity. This study provides new mechanistic details regarding how excess Msh2-Msh3 can disrupt DNA replication and repair and highlights the role of Msh2-Msh3 protein abundance in Msh2-Msh3-mediated genomic instability.
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Affiliation(s)
- Melisa Medina-Rivera
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo NY, 14203, USA
| | - Samantha Phelps
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo NY, 14203, USA
| | - Madhumita Sridharan
- Department of Biology, Indiana University Purdue University Indianapolis, Indianapolis, IN, 46202, USA
| | - Jordan Becker
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Natalie A Lamb
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo NY, 14203, USA
| | - Charanya Kumar
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo NY, 14203, USA
| | - Mark D Sutton
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo NY, 14203, USA
| | - Anja Bielinsky
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Lata Balakrishnan
- Department of Biology, Indiana University Purdue University Indianapolis, Indianapolis, IN, 46202, USA
| | - Jennifer A Surtees
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo NY, 14203, USA
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4
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Stepchenkova EI, Zadorsky SP, Shumega AR, Aksenova AY. Practical Approaches for the Yeast Saccharomyces cerevisiae Genome Modification. Int J Mol Sci 2023; 24:11960. [PMID: 37569333 PMCID: PMC10419131 DOI: 10.3390/ijms241511960] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 07/21/2023] [Accepted: 07/22/2023] [Indexed: 08/13/2023] Open
Abstract
The yeast S. cerevisiae is a unique genetic object for which a wide range of relatively simple, inexpensive, and non-time-consuming methods have been developed that allow the performing of a wide variety of genome modifications. Among the latter, one can mention point mutations, disruptions and deletions of particular genes and regions of chromosomes, insertion of cassettes for the expression of heterologous genes, targeted chromosomal rearrangements such as translocations and inversions, directed changes in the karyotype (loss or duplication of particular chromosomes, changes in the level of ploidy), mating-type changes, etc. Classical yeast genome manipulations have been advanced with CRISPR/Cas9 technology in recent years that allow for the generation of multiple simultaneous changes in the yeast genome. In this review we discuss practical applications of both the classical yeast genome modification methods as well as CRISPR/Cas9 technology. In addition, we review methods for ploidy changes, including aneuploid generation, methods for mating type switching and directed DSB. Combined with a description of useful selective markers and transformation techniques, this work represents a nearly complete guide to yeast genome modification.
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Affiliation(s)
- Elena I. Stepchenkova
- Department of Genetics and Biotechnology, St. Petersburg State University, 199034 St. Petersburg, Russia; (E.I.S.); (S.P.Z.); (A.R.S.)
- Vavilov Institute of General Genetics, St. Petersburg Branch, Russian Academy of Sciences, 199034 St. Petersburg, Russia
| | - Sergey P. Zadorsky
- Department of Genetics and Biotechnology, St. Petersburg State University, 199034 St. Petersburg, Russia; (E.I.S.); (S.P.Z.); (A.R.S.)
- Vavilov Institute of General Genetics, St. Petersburg Branch, Russian Academy of Sciences, 199034 St. Petersburg, Russia
| | - Andrey R. Shumega
- Department of Genetics and Biotechnology, St. Petersburg State University, 199034 St. Petersburg, Russia; (E.I.S.); (S.P.Z.); (A.R.S.)
| | - Anna Y. Aksenova
- Laboratory of Amyloid Biology, St. Petersburg State University, 199034 St. Petersburg, Russia
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5
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Nir Heyman S, Golan M, Liefshitz B, Kupiec M. A Role for the Interactions between Polδ and PCNA Revealed by Analysis of pol3-01 Yeast Mutants. Genes (Basel) 2023; 14:391. [PMID: 36833317 PMCID: PMC9957047 DOI: 10.3390/genes14020391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 01/30/2023] [Accepted: 01/31/2023] [Indexed: 02/05/2023] Open
Abstract
Several DNA polymerases participate in DNA synthesis during genome replication and DNA repair. PCNA, a homotrimeric ring, acts as a processivity factor for DNA polymerases. PCNA also acts as a "landing pad" for proteins that interact with chromatin and DNA at the moving fork. The interaction between PCNA and polymerase delta (Polδ) is mediated by PIPs (PCNA-interacting peptides), in particular the one on Pol32, a regulatory subunit of Polδ. Here, we demonstrate that pol3-01, an exonuclease mutant of Polδ's catalytic subunit, exhibits a weak interaction with Pol30 compared to the WT DNA polymerase. The weak interaction activates DNA bypass pathways, leading to increased mutagenesis and sister chromatid recombination. Strengthening pol3-01's weak interaction with PCNA suppresses most of the phenotypes. Our results are consistent with a model in which Pol3-01 tends to detach from the chromatin, allowing an easier replacement of Polδ by the trans-lesion synthesis polymerase Zeta (Polz), thus leading to the increased mutagenic phenotype.
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Affiliation(s)
| | | | | | - Martin Kupiec
- The Shmunis School of Biomedicine and Cancer Research, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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6
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Martín-Rufo R, de la Vega-Barranco G, Lecona E. Ubiquitin and SUMO as timers during DNA replication. Semin Cell Dev Biol 2022; 132:62-73. [PMID: 35210137 DOI: 10.1016/j.semcdb.2022.02.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Revised: 02/12/2022] [Accepted: 02/14/2022] [Indexed: 12/14/2022]
Abstract
Every time a cell copies its DNA the genetic material is exposed to the acquisition of mutations and genomic alterations that corrupt the information passed on to daughter cells. A tight temporal regulation of DNA replication is necessary to ensure the full copy of the DNA while preventing the appearance of genomic instability. Protein modification by ubiquitin and SUMO constitutes a very complex and versatile system that allows the coordinated control of protein stability, activity and interactome. In chromatin, their action is complemented by the AAA+ ATPase VCP/p97 that recognizes and removes ubiquitylated and SUMOylated factors from specific cellular compartments. The concerted action of the ubiquitin/SUMO system and VCP/p97 determines every step of DNA replication enforcing the ordered activation/inactivation, loading/unloading and stabilization/destabilization of replication factors. Here we analyze the mechanisms used by ubiquitin/SUMO and VCP/p97 to establish molecular timers throughout DNA replication and their relevance in maintaining genome stability. We propose that these PTMs are the main molecular watch of DNA replication from origin recognition to replisome disassembly.
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Affiliation(s)
- Rodrigo Martín-Rufo
- Chromatin, Cancer and the Ubiquitin System lab, Centre for Molecular Biology Severo Ochoa (CBMSO, CSIC-UAM), Department of Genome Dynamics and Function, Madrid 28049, Spain
| | - Guillermo de la Vega-Barranco
- Chromatin, Cancer and the Ubiquitin System lab, Centre for Molecular Biology Severo Ochoa (CBMSO, CSIC-UAM), Department of Genome Dynamics and Function, Madrid 28049, Spain
| | - Emilio Lecona
- Chromatin, Cancer and the Ubiquitin System lab, Centre for Molecular Biology Severo Ochoa (CBMSO, CSIC-UAM), Department of Genome Dynamics and Function, Madrid 28049, Spain.
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7
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Saccharomyces cerevisiae DNA repair pathways involved in repair of lesions induced by mixed ternary mononuclear Cu(II) complexes based on valproic acid with 1,10-phenanthroline or 2,2'- bipyridine ligands. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2021; 868-869:503390. [PMID: 34454693 DOI: 10.1016/j.mrgentox.2021.503390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Revised: 07/25/2021] [Accepted: 08/07/2021] [Indexed: 11/21/2022]
Abstract
The sodium valproate has been largely used as an anti-epilepsy drug and, recently, as a putative drug in cancer therapy. However, the treatment with sodium valproate has some adverse effects. In this sense, more effective and secure complexes than sodium valproate should be explored in searching for new active drugs. This study aims to evaluate the cytotoxicity of sodium valproate, mixed ternary mononuclear Cu(II) complexes based on valproic acid (VA) with 1,10-phenanthroline (Phen) or 2,2'- bipyridine (Bipy) ligands - [Cu2(Valp)4], [Cu(Valp)2Phen] and [Cu(Valp)2Bipy] - in yeast Saccharomyces cerevisiae, proficient or deficient in different repair pathways, such as base excision repair (BER), nucleotide excision repair (NER), translesion synthesis (TLS), DNA postreplication repair (PRR), homologous recombination (HR) and non-homologous end-joining (NHEJ). The results indicated that the Cu(II) complexes have higher cytotoxicity than sodium valproate in the following order: [Cu(Valp)2Phen] > [Cu(Valp)2Bipy] > [Cu2(Valp)4] > sodium valproate. The treatment with Cu(II) complexes and sodium valproate induced mutations in S. cerevisiae. The data indicated that yeast strains deficient in BER (Ogg1p), NER (complex Rad1p-Rad10p) or TLS (Rev1p, Rev3p and Rad30p) proteins are associated with increased sensitivity to sodium valproate. The BER mutants (ogg1Δ, apn1Δ, rad27Δ, ntg1Δ and ntg2Δ) showed increased sensitivity to Cu(II) complexes. DNA damage induced by the complexes requires proteins from NER (Rad1p and Rad10p), TLS (Rev1p, Rev3p and Rad30p), PRR (Rad6 and Rad18p) and HR (Rad52p and Rad50p) for efficient repair. Therefore, Cu(II) complexes display enhanced cytotoxicity when compared to the sodium valproate and induce distinct DNA lesions, indicating a potential application as cytotoxic agents.
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8
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Arbel M, Liefshitz B, Kupiec M. DNA damage bypass pathways and their effect on mutagenesis in yeast. FEMS Microbiol Rev 2021; 45:5896953. [PMID: 32840566 DOI: 10.1093/femsre/fuaa038] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 08/23/2020] [Indexed: 12/11/2022] Open
Abstract
What is the origin of mutations? In contrast to the naïve notion that mutations are unfortunate accidents, genetic research in microorganisms has demonstrated that most mutations are created by genetically encoded error-prone repair mechanisms. However, error-free repair pathways also exist, and it is still unclear how cells decide when to use one repair method or the other. Here, we summarize what is known about the DNA damage tolerance mechanisms (also known as post-replication repair) for perhaps the best-studied organism, the yeast Saccharomyces cerevisiae. We describe the latest research, which has established the existence of at least two error-free and two error-prone inter-related mechanisms of damage tolerance that compete for the handling of spontaneous DNA damage. We explore what is known about the induction of mutations by DNA damage. We point to potential paradoxes and to open questions that still remain unanswered.
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Affiliation(s)
- Matan Arbel
- The Shmunis School of Biomedicine and Cancer Research, Tel Aviv University, Ramat Aviv 69978, Israel
| | - Batia Liefshitz
- The Shmunis School of Biomedicine and Cancer Research, Tel Aviv University, Ramat Aviv 69978, Israel
| | - Martin Kupiec
- The Shmunis School of Biomedicine and Cancer Research, Tel Aviv University, Ramat Aviv 69978, Israel
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9
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Li T, Petreaca RC, Forsburg SL. Schizosaccharomyces pombe KAT5 contributes to resection and repair of a DNA double-strand break. Genetics 2021; 218:6173406. [PMID: 33723569 DOI: 10.1093/genetics/iyab042] [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: 02/02/2021] [Accepted: 03/04/2021] [Indexed: 11/14/2022] Open
Abstract
Chromatin remodeling is essential for effective repair of a DNA double-strand break (DSB). KAT5 (Schizosaccharomyces pombe Mst1, human TIP60) is a MYST family histone acetyltransferase conserved from yeast to humans that coordinates various DNA damage response activities at a DNA DSB, including histone remodeling and activation of the DNA damage checkpoint. In S. pombe, mutations in mst1+ causes sensitivity to DNA damaging drugs. Here we show that Mst1 is recruited to DSBs. Mutation of mst1+ disrupts recruitment of repair proteins and delays resection. These defects are partially rescued by deletion of pku70, which has been previously shown to antagonize repair by homologous recombination (HR). These phenotypes of mst1 are similar to pht1-4KR, a nonacetylatable form of histone variant H2A.Z, which has been proposed to affect resection. Our data suggest that Mst1 functions to direct repair of DSBs toward HR pathways by modulating resection at the DSB.
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Affiliation(s)
- Tingting Li
- Program of Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089-2910, USA
| | - Ruben C Petreaca
- Program of Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089-2910, USA
- Department of Molecular Genetics, Ohio State University, Marion, OH 43302, USA
| | - Susan L Forsburg
- Program of Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089-2910, USA
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10
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Paeschke K, Burkovics P. Mgs1 function at G-quadruplex structures during DNA replication. Curr Genet 2020; 67:225-230. [PMID: 33237336 PMCID: PMC8032586 DOI: 10.1007/s00294-020-01128-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 10/27/2020] [Accepted: 10/29/2020] [Indexed: 11/03/2022]
Abstract
The coordinated action of DNA polymerases and DNA helicases is essential at genomic sites that are hard to replicate. Among these are sites that harbour G-quadruplex DNA structures (G4). G4s are stable alternative DNA structures, which have been implicated to be involved in important cellular processes like the regulation of gene expression or telomere maintenance. G4 structures were shown to hinder replication fork progression and cause genomic deletions, mutations and recombination events. Many helicases unwind G4 structures and preserve genome stability, but a detailed understanding of G4 replication and the re-start of stalled replication forks around formed G4 structures is not clear, yet. In our recent study, we identified that Mgs1 preferentially binds to G4 DNA structures in vitro and is associated with putative G4-forming chromosomal regions in vivo. Mgs1 binding to G4 motifs in vivo is partially dependent on the helicase Pif1. Pif1 is the major G4-unwinding helicase in S. cerevisiae. In the absence of Mgs1, we determined elevated gross chromosomal rearrangement (GCR) rates in yeast, similar to Pif1 deletion. Here, we highlight the recent findings and set these into context with a new mechanistic model. We propose that Mgs1's functions support DNA replication at G4-forming regions.
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Affiliation(s)
- Katrin Paeschke
- Department of Oncology, Hematology and Rheumatology, University Hospital Bonn, Bonn, Germany.
| | - Peter Burkovics
- Institute of Genetics, Biological Research Centre, Szeged, Hungary.
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11
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Lehmann CP, Jiménez-Martín A, Branzei D, Tercero JA. Prevention of unwanted recombination at damaged replication forks. Curr Genet 2020; 66:1045-1051. [PMID: 32671464 PMCID: PMC7599154 DOI: 10.1007/s00294-020-01095-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 07/01/2020] [Accepted: 07/08/2020] [Indexed: 02/07/2023]
Abstract
Homologous recombination is essential for the maintenance of genome integrity but must be strictly controlled to avoid dangerous outcomes that produce the opposite effect, genomic instability. During unperturbed chromosome replication, recombination is globally inhibited at ongoing DNA replication forks, which helps to prevent deleterious genomic rearrangements. This inhibition is carried out by Srs2, a helicase that binds to SUMOylated PCNA and has an anti-recombinogenic function at replication forks. However, at damaged stalled forks, Srs2 is counteracted and DNA lesion bypass can be achieved by recombination-mediated template switching. In budding yeast, template switching is dependent on Rad5. In the absence of this protein, replication forks stall in the presence of DNA lesions and cells die. Recently, we showed that in cells lacking Rad5 that are exposed to DNA damage or replicative stress, elimination of the conserved Mgs1/WRNIP1 ATPase allows an alternative mode of DNA damage bypass that is driven by recombination and facilitates completion of chromosome replication and cell viability. We have proposed that Mgs1 is important to prevent a potentially harmful salvage pathway of recombination at damaged stalled forks. In this review, we summarize our current understanding of how unwanted recombination is prevented at damaged stalled replication forks.
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Affiliation(s)
- Carl P Lehmann
- Centro de Biología Molecular Severo Ochoa (CSIC/UAM), Cantoblanco, 28049, Madrid, Spain
| | - Alberto Jiménez-Martín
- Centro de Biología Molecular Severo Ochoa (CSIC/UAM), Cantoblanco, 28049, Madrid, Spain.,Centro Andaluz de Biología del Desarrollo (CSIC/UPO), 41013, Seville, Spain
| | - Dana Branzei
- IFOM, The FIRC Institute of Molecular Oncology, Via Adamello 16, 20139, Milan, Italy.,Istituto di Genetica Molecolare, Consiglio Nazionale delle Ricerche (IGM-CNR), Via Abbiategrasso 207, 27100, Pavia, Italy
| | - José Antonio Tercero
- Centro de Biología Molecular Severo Ochoa (CSIC/UAM), Cantoblanco, 28049, Madrid, Spain.
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