1
|
Shah SB, Li Y, Li S, Hu Q, Wu T, Shi Y, Nguyen T, Ive I, Shi L, Wang H, Wu X. 53BP1 deficiency leads to hyperrecombination using break-induced replication (BIR). Nat Commun 2024; 15:8648. [PMID: 39368985 PMCID: PMC11455893 DOI: 10.1038/s41467-024-52916-z] [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: 04/18/2024] [Accepted: 09/19/2024] [Indexed: 10/07/2024] Open
Abstract
Break-induced replication (BIR) is mutagenic, and thus its use requires tight regulation, yet the underlying mechanisms remain elusive. Here we uncover an important role of 53BP1 in suppressing BIR after end resection at double strand breaks (DSBs), distinct from its end protection activity, providing insight into the mechanisms governing BIR regulation and DSB repair pathway selection. We demonstrate that loss of 53BP1 induces BIR-like hyperrecombination, in a manner dependent on Polα-primase-mediated end fill-in DNA synthesis on single-stranded DNA (ssDNA) overhangs at DSBs, leading to PCNA ubiquitination and PIF1 recruitment to activate BIR. On broken replication forks, where BIR is required for repairing single-ended DSBs (seDSBs), SMARCAD1 displaces 53BP1 to facilitate the localization of ubiquitinated PCNA and PIF1 to DSBs for BIR activation. Hyper BIR associated with 53BP1 deficiency manifests template switching and large deletions, underscoring another aspect of 53BP1 in suppressing genome instability. The synthetic lethal interaction between the 53BP1 and BIR pathways provides opportunities for targeted cancer treatment.
Collapse
Affiliation(s)
- Sameer Bikram Shah
- Department of Molecular and Cell Biology, The Scripps Research Institute, La Jolla, CA, 92037, USA
| | - Youhang Li
- Department of Molecular and Cell Biology, The Scripps Research Institute, La Jolla, CA, 92037, USA
- College of Life Science, Capital Normal University, Beijing, 100037, China
| | - Shibo Li
- Department of Molecular and Cell Biology, The Scripps Research Institute, La Jolla, CA, 92037, USA
- College of Life Sciences, Tianjin Normal University, Tianjin, 300387, China
| | - Qing Hu
- Department of Molecular and Cell Biology, The Scripps Research Institute, La Jolla, CA, 92037, USA
| | - Tong Wu
- Department of Molecular and Cell Biology, The Scripps Research Institute, La Jolla, CA, 92037, USA
| | - Yanmeng Shi
- Department of Molecular and Cell Biology, The Scripps Research Institute, La Jolla, CA, 92037, USA
| | - Tran Nguyen
- Department of Molecular and Cell Biology, The Scripps Research Institute, La Jolla, CA, 92037, USA
| | - Isaac Ive
- Department of Molecular and Cell Biology, The Scripps Research Institute, La Jolla, CA, 92037, USA
| | - Linda Shi
- The Institute of Engineering in Medicine, University of California, San Diego, California, 92093, USA
| | - Hailong Wang
- College of Life Science, Capital Normal University, Beijing, 100037, China
| | - Xiaohua Wu
- Department of Molecular and Cell Biology, The Scripps Research Institute, La Jolla, CA, 92037, USA.
| |
Collapse
|
2
|
Triplett MK, Johnson MJ, Symington LS. Induction of homologous recombination by site-specific replication stress. DNA Repair (Amst) 2024; 142:103753. [PMID: 39190984 PMCID: PMC11425181 DOI: 10.1016/j.dnarep.2024.103753] [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: 05/23/2024] [Revised: 08/07/2024] [Accepted: 08/12/2024] [Indexed: 08/29/2024]
Abstract
DNA replication stress is one of the primary causes of genome instability. In response to replication stress, cells can employ replication restart mechanisms that rely on homologous recombination to resume replication fork progression and preserve genome integrity. In this review, we provide an overview of various methods that have been developed to induce site-specific replication fork stalling or collapse in eukaryotic cells. In particular, we highlight recent studies of mechanisms of replication-associated recombination resulting from site-specific protein-DNA barriers and single-strand breaks, and we discuss the contributions of these findings to our understanding of the consequences of these forms of stress on genome stability.
Collapse
Affiliation(s)
- Marina K Triplett
- Integrated Program in Cellular, Molecular, and Biomedical Studies, Columbia University Irving Medical Center, New York, NY 10032, United States; Department of Microbiology & Immunology, Columbia University Irving Medical Center, New York, NY 10032, United States
| | - Matthew J Johnson
- Department of Microbiology & Immunology, Columbia University Irving Medical Center, New York, NY 10032, United States; Program in Biological Sciences, Columbia University, New York, NY 10027, United States
| | - Lorraine S Symington
- Department of Microbiology & Immunology, Columbia University Irving Medical Center, New York, NY 10032, United States; Department of Genetics & Development, Columbia University Irving Medical Center, New York, NY 10032, United States.
| |
Collapse
|
3
|
Lee RS, Twarowski JM, Malkova A. Stressed? Break-induced replication comes to the rescue! DNA Repair (Amst) 2024; 142:103759. [PMID: 39241677 DOI: 10.1016/j.dnarep.2024.103759] [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: 05/23/2024] [Revised: 08/22/2024] [Accepted: 08/26/2024] [Indexed: 09/09/2024]
Abstract
Break-induced replication (BIR) is a homologous recombination (HR) pathway that repairs one-ended DNA double-strand breaks (DSBs), which can result from replication fork collapse, telomere erosion, and other events. Eukaryotic BIR has been mainly investigated in yeast, where it is initiated by invasion of the broken DNA end into a homologous sequence, followed by extensive replication synthesis proceeding to the chromosome end. Multiple recent studies have described BIR in mammalian cells, the properties of which show many similarities to yeast BIR. While HR is considered as "error-free" mechanism, BIR is highly mutagenic and frequently leads to chromosomal rearrangements-genetic instabilities known to promote human disease. In addition, it is now recognized that BIR is highly stimulated by replication stress (RS), including RS constantly present in cancer cells, implicating BIR as a contributor to cancer genesis and progression. Here, we discuss the past and current findings related to the mechanism of BIR, the association of BIR with replication stress, and the destabilizing effects of BIR on the eukaryotic genome. Finally, we consider the potential for exploiting the BIR machinery to develop anti-cancer therapeutics.
Collapse
Affiliation(s)
- Rosemary S Lee
- Department of Biochemistry & Structural Biology, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | | | - Anna Malkova
- Department of Biochemistry & Structural Biology, University of Texas Health San Antonio, San Antonio, TX 78229, USA.
| |
Collapse
|
4
|
Shah SB, Li Y, Li S, Hu Q, Wu T, Shi Y, Nguyen T, Ive I, Shi L, Wang H, Wu X. 53BP1 deficiency leads to hyperrecombination using break-induced replication (BIR). BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.09.11.612483. [PMID: 39314326 PMCID: PMC11419065 DOI: 10.1101/2024.09.11.612483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/25/2024]
Abstract
Break-induced replication (BIR) is mutagenic, and thus its use requires tight regulation, yet the underlying mechanisms remain elusive. Here we uncover an important role of 53BP1 in suppressing BIR after end resection at double strand breaks (DSBs), distinct from its end protection activity, providing insight into the mechanisms governing BIR regulation and DSB repair pathway selection. We demonstrate that loss of 53BP1 induces BIR-like hyperrecombination, in a manner dependent on Polα-primase-mediated end fill-in DNA synthesis on single-stranded DNA (ssDNA) overhangs at DSBs, leading to PCNA ubiquitination and PIF1 recruitment to activate BIR. On broken replication forks, where BIR is required for repairing single-ended DSBs (seDSBs), SMARCAD1 displaces 53BP1 to facilitate the localization of ubiquitinated PCNA and PIF1 to DSBs for BIR activation. Hyper BIR associated with 53BP1 deficiency manifests template switching and large deletions, underscoring another aspect of 53BP1 in suppressing genome instability. The synthetic lethal interaction between the 53BP1 and BIR pathways provides opportunities for targeted cancer treatment.
Collapse
Affiliation(s)
- Sameer Bikram Shah
- Department of Molecular and Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Youhang Li
- Department of Molecular and Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
- College of Life Science, Capital Normal University, Beijing 100037, China
| | - Shibo Li
- Department of Molecular and Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
- College of Life Sciences, Tianjin Normal University, Tianjin, 300387, China
| | - Qing Hu
- Department of Molecular and Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Tong Wu
- Department of Molecular and Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Yanmeng Shi
- Department of Molecular and Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Tran Nguyen
- Department of Molecular and Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Isaac Ive
- Department of Molecular and Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Linda Shi
- The Institute of Engineering in Medicine, University of California, San Diego, California 92093, USA
| | - Hailong Wang
- College of Life Science, Capital Normal University, Beijing 100037, China
| | - Xiaohua Wu
- Department of Molecular and Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| |
Collapse
|
5
|
Bainbridge LJ, Daigaku Y. Bulk synthesis and beyond: The roles of eukaryotic replicative DNA polymerases. DNA Repair (Amst) 2024; 141:103740. [PMID: 39096696 DOI: 10.1016/j.dnarep.2024.103740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2024] [Revised: 07/27/2024] [Accepted: 07/28/2024] [Indexed: 08/05/2024]
Abstract
An organism's genomic DNA must be accurately duplicated during each cell cycle. DNA synthesis is catalysed by DNA polymerase enzymes, which extend nucleotide polymers in a 5' to 3' direction. This inherent directionality necessitates that one strand is synthesised forwards (leading), while the other is synthesised backwards discontinuously (lagging) to couple synthesis to the unwinding of duplex DNA. Eukaryotic cells possess many diverse polymerases that coordinate to replicate DNA, with the three main replicative polymerases being Pol α, Pol δ and Pol ε. Studies conducted in yeasts and human cells utilising mutant polymerases that incorporate molecular signatures into nascent DNA implicate Pol ε in leading strand synthesis and Pol α and Pol δ in lagging strand replication. Recent structural insights have revealed how the spatial organization of these enzymes around the core helicase facilitates their strand-specific roles. However, various challenging situations during replication require flexibility in the usage of these enzymes, such as during replication initiation or encounters with replication-blocking adducts. This review summarises the roles of the replicative polymerases in bulk DNA replication and explores their flexible and dynamic deployment to complete genome replication. We also examine how polymerase usage patterns can inform our understanding of global replication dynamics by revealing replication fork directionality to identify regions of replication initiation and termination.
Collapse
Affiliation(s)
- Lewis J Bainbridge
- Cancer Genome Dynamics Project, Cancer Institute, Japanese Foundation for Cancer Research, Tokyo, Japan
| | - Yasukazu Daigaku
- Cancer Genome Dynamics Project, Cancer Institute, Japanese Foundation for Cancer Research, Tokyo, Japan.
| |
Collapse
|
6
|
Norris JL, Hedglin M. Direct, ensemble FRET approaches to monitor transient state kinetics of human DNA polymerase δ holoenzyme assembly and initiation of DNA synthesis. Methods Enzymol 2024; 705:271-309. [PMID: 39389667 DOI: 10.1016/bs.mie.2024.08.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/12/2024]
Abstract
In humans, DNA polymerase δ (pol δ) holoenzymes, comprised of pol δ and the processivity sliding clamp, proliferating cell nuclear antigen (PCNA), carry out DNA synthesis during lagging strand replication, the initiation of leading strand DNA replication as well as most of the major DNA damage repair pathways. In each of these contexts, pol δ holoenzymes are assembled at primer/template (P/T) junctions and initiate DNA synthesis in a stepwise process that involves the PCNA clamp loader, replication factor C and, depending on the DNA synthesis pathway, the major single strand DNA-binding protein complex, replication protein A (RPA). In a recent report from our laboratory, we designed and utilized direct, ensemble Förster Resonance Energy Transfer approaches to monitor the transient state kinetics of pol δ holoenzyme assembly and initiation of DNA synthesis on P/T junctions engaged by RPA. In this chapter, we detail the original approaches and discuss adaptations that can be utilized to monitor fast kinetic reactions in the millisecond (ms) timescale. All approaches described in this chapter utilize a commercially-available fluorescence spectrophotometer, can be readily evolved for alternative DNA polymerases and P/T DNA substrates, and permit incorporation of protein posttranslational modifications, accessory factors, DNA covalent modifications, accessory factors, enzymes, etc. Hence, these approaches are widely accessible and broadly applicable for characterizing DNA polymerase holoenzyme assembly and initiation of DNA synthesis during any PCNA-dependent DNA synthesis pathway.
Collapse
Affiliation(s)
- Jessica L Norris
- Department of Chemistry, The Pennsylvania State University, University Park, PA, United States
| | - Mark Hedglin
- Department of Chemistry, The Pennsylvania State University, University Park, PA, United States.
| |
Collapse
|
7
|
Hong Z, Byrd AK, Gao J, Das P, Tan VQ, Malone EG, Osei B, Marecki JC, Protacio RU, Wahls WP, Raney KD, Song H. Eukaryotic Pif1 helicase unwinds G-quadruplex and dsDNA using a conserved wedge. Nat Commun 2024; 15:6104. [PMID: 39030241 PMCID: PMC11275212 DOI: 10.1038/s41467-024-50575-8] [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: 12/11/2023] [Accepted: 07/16/2024] [Indexed: 07/21/2024] Open
Abstract
G-quadruplexes (G4s) formed by guanine-rich nucleic acids induce genome instability through impeding DNA replication fork progression. G4s are stable DNA structures, the unfolding of which require the functions of DNA helicases. Pif1 helicase binds preferentially to G4 DNA and plays multiple roles in maintaining genome stability, but the mechanism by which Pif1 unfolds G4s is poorly understood. Here we report the co-crystal structure of Saccharomyces cerevisiae Pif1 (ScPif1) bound to a G4 DNA with a 5' single-stranded DNA (ssDNA) segment. Unlike the Thermus oshimai Pif1-G4 structure, in which the 1B and 2B domains confer G4 recognition, ScPif1 recognizes G4 mainly through the wedge region in the 1A domain that contacts the 5' most G-tetrad directly. A conserved Arg residue in the wedge is required for Okazaki fragment processing but not for mitochondrial function or for suppression of gross chromosomal rearrangements. Multiple substitutions at this position have similar effects on resolution of DNA duplexes and G4s, suggesting that ScPif1 may use the same wedge to unwind G4 and dsDNA. Our results reveal the mechanism governing dsDNA unwinding and G4 unfolding by ScPif1 helicase that can potentially be generalized to other eukaryotic Pif1 helicases and beyond.
Collapse
Affiliation(s)
- Zebin Hong
- Institute of Molecular and Cell Biology (IMCB), Agency for Science, Technology and Research (A*STAR), Proteos, Singapore, Republic of Singapore
| | - Alicia K Byrd
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR, USA.
| | - Jun Gao
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Poulomi Das
- Institute of Molecular and Cell Biology (IMCB), Agency for Science, Technology and Research (A*STAR), Proteos, Singapore, Republic of Singapore
| | - Vanessa Qianmin Tan
- Institute of Molecular and Cell Biology (IMCB), Agency for Science, Technology and Research (A*STAR), Proteos, Singapore, Republic of Singapore
| | - Emory G Malone
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Bertha Osei
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - John C Marecki
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Reine U Protacio
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Wayne P Wahls
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Kevin D Raney
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR, USA.
| | - Haiwei Song
- Institute of Molecular and Cell Biology (IMCB), Agency for Science, Technology and Research (A*STAR), Proteos, Singapore, Republic of Singapore.
| |
Collapse
|
8
|
Carreira R, Lama-Diaz T, Crugeiras M, Aguado F, Sebesta M, Krejci L, Blanco M. Concurrent D-loop cleavage by Mus81 and Yen1 yields half-crossover precursors. Nucleic Acids Res 2024; 52:7012-7030. [PMID: 38832625 PMCID: PMC11229367 DOI: 10.1093/nar/gkae453] [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: 09/22/2023] [Revised: 05/05/2024] [Accepted: 05/14/2024] [Indexed: 06/05/2024] Open
Abstract
Homologous recombination involves the formation of branched DNA molecules that may interfere with chromosome segregation. To resolve these persistent joint molecules, cells rely on the activation of structure-selective endonucleases (SSEs) during the late stages of the cell cycle. However, the premature activation of SSEs compromises genome integrity, due to untimely processing of replication and/or recombination intermediates. Here, we used a biochemical approach to show that the budding yeast SSEs Mus81 and Yen1 possess the ability to cleave the central recombination intermediate known as the displacement loop or D-loop. Moreover, we demonstrate that, consistently with previous genetic data, the simultaneous action of Mus81 and Yen1, followed by ligation, is sufficient to recreate the formation of a half-crossover precursor in vitro. Our results provide not only mechanistic explanation for the formation of a half-crossover, but also highlight the critical importance for precise regulation of these SSEs to prevent chromosomal rearrangements.
Collapse
Affiliation(s)
- Raquel Carreira
- Department of Biochemistry and Molecular Biology, CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria (IDIS), Santiago de Compostela, A Coruña 15782, Spain
| | - Tomas Lama-Diaz
- Department of Biochemistry and Molecular Biology, CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria (IDIS), Santiago de Compostela, A Coruña 15782, Spain
| | - Maria Crugeiras
- Department of Biochemistry and Molecular Biology, CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria (IDIS), Santiago de Compostela, A Coruña 15782, Spain
| | - F Javier Aguado
- Department of Biochemistry and Molecular Biology, CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria (IDIS), Santiago de Compostela, A Coruña 15782, Spain
| | - Marek Sebesta
- Department of Biology and National Centre for Biomolecular Research, Masaryk University, Brno 62500, Czech Republic
| | - Lumir Krejci
- Department of Biology and National Centre for Biomolecular Research, Masaryk University, Brno 62500, Czech Republic
| | - Miguel G Blanco
- Department of Biochemistry and Molecular Biology, CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria (IDIS), Santiago de Compostela, A Coruña 15782, Spain
| |
Collapse
|
9
|
Lama-Diaz T, Blanco MG. Alternative translation initiation by ribosomal leaky scanning produces multiple isoforms of the Pif1 helicase. Nucleic Acids Res 2024; 52:6928-6944. [PMID: 38783074 PMCID: PMC11229318 DOI: 10.1093/nar/gkae400] [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: 11/13/2023] [Revised: 04/24/2024] [Accepted: 05/01/2024] [Indexed: 05/25/2024] Open
Abstract
In budding yeast, the integrity of both the nuclear and mitochondrial genomes relies on dual-targeted isoforms of the conserved Pif1 helicase, generated by alternative translation initiation (ATI) of PIF1 mRNA from two consecutive AUG codons flanking a mitochondrial targeting signal. Here, we demonstrate that ribosomal leaky scanning is the specific ATI mechanism that produces not only these, but also novel, previously uncharacterized Pif1 isoforms. Both in-frame, downstream AUGs as well as near-cognate start codons contribute to the generation of these alternative isoforms. This has crucial implications for the rational design of genuine separation-of-function alleles and provides an explanation for the suboptimal behaviour of the widely employed mitochondrial- (pif1-m1) and nuclear-deficient (pif1-m2) alleles, with mutations in the first or second AUG codon, respectively. We have taken advantage of this refined model to develop improved versions of these alleles, which will serve as valuable tools to elucidate novel functions of this helicase and to disambiguate previously described genetic interactions of PIF1 in the context of nuclear and mitochondrial genome stability.
Collapse
Affiliation(s)
- Tomas Lama-Diaz
- Department of Biochemistry and Molecular Biology, CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria (IDIS), Santiago de Compostela, A Coruña 15782, Spain
| | - Miguel G Blanco
- Department of Biochemistry and Molecular Biology, CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria (IDIS), Santiago de Compostela, A Coruña 15782, Spain
| |
Collapse
|
10
|
Bessho T. Up-Regulation of Non-Homologous End-Joining by MUC1. Genes (Basel) 2024; 15:808. [PMID: 38927743 PMCID: PMC11203369 DOI: 10.3390/genes15060808] [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: 05/08/2024] [Revised: 06/10/2024] [Accepted: 06/15/2024] [Indexed: 06/28/2024] Open
Abstract
Ionizing radiation (IR) and chemotherapy with DNA-damaging drugs such as cisplatin are vital cancer treatment options. These treatments induce double-strand breaks (DSBs) as cytotoxic DNA damage; thus, the DSB repair activity in each cancer cell significantly influences the efficacy of the treatments. Pancreatic cancers are known to be resistant to these treatments, and the overexpression of MUC1, a member of the glycoprotein mucins, is associated with IR- and chemo-resistance. Therefore, we investigated the impact of MUC1 on DSB repair. This report examined the effect of the overexpression of MUC1 on homologous recombination (HR) and non-homologous end-joining (NHEJ) using cell-based DSB repair assays. In addition, the therapeutic potential of NHEJ inhibitors including HDAC inhibitors was also studied using pancreatic cancer cell lines. The MUC1-overexpression enhances NHEJ, while partially suppressing HR. Also, MUC1-overexpressed cancer cell lines are preferentially killed by a DNA-PK inhibitor and HDAC1/2 inhibitors. Altogether, MUC1 induces metabolic changes that create an imbalance between NHEJ and HR activities, and this imbalance can be a target for selective killing by HDAC inhibitors. This is a novel mechanism of MUC1-mediated IR-resistance and will form the basis for targeting MUC1-overexpressed pancreatic cancer.
Collapse
Affiliation(s)
- Tadayoshi Bessho
- The Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, 986805 Nebraska Medical Center, Omaha, NE 68198, USA
| |
Collapse
|
11
|
Kimble MT, Sane A, Reid RJ, Johnson MJ, Rothstein R, Symington LS. Strand asymmetry in the repair of replication dependent double-strand breaks. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.17.598707. [PMID: 38948862 PMCID: PMC11212877 DOI: 10.1101/2024.06.17.598707] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/02/2024]
Abstract
Single-strand breaks (SSBs) are one of the most common endogenous lesions and have the potential to give rise to cytotoxic double-strand breaks (DSBs) during DNA replication. To investigate the mechanism of replication fork collapse at SSBs and subsequent repair, we employed Cas9 nickase (nCas9) to generate site and strand-specific nicks in the budding yeast genome. We show that nCas9-induced nicks are converted to mostly double-ended DSBs during S-phase. We find that repair of replication-dependent DSBs requires homologous recombination (HR) and is independent of canonical non-homologous end joining. Consistent with a strong bias to repair these lesions using a sister chromatid template, we observe minimal induction of inter-chromosomal HR by nCas9. Using nCas9 and a gRNA to nick either the leading or lagging strand template, we carried out a genome-wide screen to identify factors necessary for the repair of replication-dependent DSBs. All the core HR genes were recovered in the screen with both gRNAs, but we recovered components of the replication-coupled nucleosome assembly (RCNA) pathway with only the gRNA targeting the leading strand template. By use of additional gRNAs, we find that the RCNA pathway is especially important to repair a leading strand fork collapse.
Collapse
|
12
|
Kotenko O, Makovets S. The functional significance of the RPA- and PCNA-dependent recruitment of Pif1 to DNA. EMBO Rep 2024; 25:1734-1751. [PMID: 38480846 PMCID: PMC11014909 DOI: 10.1038/s44319-024-00114-9] [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: 08/19/2023] [Revised: 02/10/2024] [Accepted: 02/26/2024] [Indexed: 04/14/2024] Open
Abstract
Pif1 family helicases are multifunctional proteins conserved in eukaryotes, from yeast to humans. They are important for the genome maintenance in both nuclei and mitochondria, where they have been implicated in Okazaki fragment processing, replication fork progression and termination, telomerase regulation and DNA repair. While the Pif1 helicase activity is readily detectable on naked nucleic acids in vitro, the in vivo functions rely on recruitment to DNA. We identify the single-stranded DNA binding protein complex RPA as the major recruiter of Pif1 in budding yeast, in addition to the previously reported Pif1-PCNA interaction. The two modes of the Pif1 recruitment act independently during telomerase inhibition, as the mutations in the Pif1 motifs disrupting either of the recruitment pathways act additively. In contrast, both recruitment mechanisms are essential for the replication-related roles of Pif1 at conventional forks and during the repair by break-induced replication. We propose a molecular model where RPA and PCNA provide a double anchoring of Pif1 at replication forks, which is essential for the Pif1 functions related to the fork movement.
Collapse
Affiliation(s)
- Oleksii Kotenko
- Institute of Cell Biology, University of Edinburgh, King's Buildings, Alexander Crum Brown Road, Edinburgh, EH9 3FF, UK
| | - Svetlana Makovets
- Institute of Cell Biology, University of Edinburgh, King's Buildings, Alexander Crum Brown Road, Edinburgh, EH9 3FF, UK.
| |
Collapse
|
13
|
Showman S, Talbert PB, Xu Y, Adeyemi RO, Henikoff S. Expansion of human centromeric arrays in cells undergoing break-induced replication. Cell Rep 2024; 43:113851. [PMID: 38427559 PMCID: PMC11034957 DOI: 10.1016/j.celrep.2024.113851] [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: 11/11/2023] [Revised: 01/10/2024] [Accepted: 02/07/2024] [Indexed: 03/03/2024] Open
Abstract
Human centromeres are located within α-satellite arrays and evolve rapidly, which can lead to individual variation in array length. Proposed mechanisms for such alterations in length are unequal crossover between sister chromatids, gene conversion, and break-induced replication. However, the underlying molecular mechanisms responsible for the massive, complex, and homogeneous organization of centromeric arrays have not been experimentally validated. Here, we use droplet digital PCR assays to demonstrate that centromeric arrays can expand and contract within ∼20 somatic cell divisions of an alternative lengthening of telomere (ALT)-positive cell line. We find that the frequency of array variation among single-cell-derived subclones ranges from a minimum of ∼7% to a maximum of ∼100%. Further clonal evolution revealed that centromere expansion is favored over contraction. We find that the homologous recombination protein RAD52 and the helicase PIF1 are required for extensive array change, suggesting that centromere sequence evolution can occur via break-induced replication.
Collapse
Affiliation(s)
- Soyeon Showman
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA; Molecular and Cellular Biology Graduate Program, University of Washington, Seattle, WA 98195, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - Paul B Talbert
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - Yiling Xu
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - Richard O Adeyemi
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
| | - Steven Henikoff
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA.
| |
Collapse
|
14
|
Ito M, Fujita Y, Shinohara A. Positive and negative regulators of RAD51/DMC1 in homologous recombination and DNA replication. DNA Repair (Amst) 2024; 134:103613. [PMID: 38142595 DOI: 10.1016/j.dnarep.2023.103613] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Revised: 12/10/2023] [Accepted: 12/10/2023] [Indexed: 12/26/2023]
Abstract
RAD51 recombinase plays a central role in homologous recombination (HR) by forming a nucleoprotein filament on single-stranded DNA (ssDNA) to catalyze homology search and strand exchange between the ssDNA and a homologous double-stranded DNA (dsDNA). The catalytic activity of RAD51 assembled on ssDNA is critical for the DNA-homology-mediated repair of DNA double-strand breaks in somatic and meiotic cells and restarting stalled replication forks during DNA replication. The RAD51-ssDNA complex also plays a structural role in protecting the regressed/reversed replication fork. Two types of regulators control RAD51 filament formation, stability, and dynamics, namely positive regulators, including mediators, and negative regulators, so-called remodelers. The appropriate balance of action by the two regulators assures genome stability. This review describes the roles of positive and negative RAD51 regulators in HR and DNA replication and its meiosis-specific homolog DMC1 in meiotic recombination. We also provide future study directions for a comprehensive understanding of RAD51/DMC1-mediated regulation in maintaining and inheriting genome integrity.
Collapse
Affiliation(s)
- Masaru Ito
- Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan.
| | - Yurika Fujita
- Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan.
| | - Akira Shinohara
- Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan.
| |
Collapse
|
15
|
Al Zouabi L, Stefanutti M, Roumeliotis S, Le Meur G, Boumard B, Riddiford N, Rubanova N, Bohec M, Gervais L, Servant N, Bardin AJ. Molecular underpinnings and environmental drivers of loss of heterozygosity in Drosophila intestinal stem cells. Cell Rep 2023; 42:113485. [PMID: 38032794 DOI: 10.1016/j.celrep.2023.113485] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 09/29/2023] [Accepted: 11/08/2023] [Indexed: 12/02/2023] Open
Abstract
During development and aging, genome mutation leading to loss of heterozygosity (LOH) can uncover recessive phenotypes within tissue compartments. This phenomenon occurs in normal human tissues and is prevalent in pathological genetic conditions and cancers. While studies in yeast have defined DNA repair mechanisms that can promote LOH, the predominant pathways and environmental triggers in somatic tissues of multicellular organisms are not well understood. Here, we investigate mechanisms underlying LOH in intestinal stem cells in Drosophila. Infection with the pathogenic bacteria, Erwinia carotovora carotovora 15, but not Pseudomonas entomophila, increases LOH frequency. Using whole genome sequencing of somatic LOH events, we demonstrate that they arise primarily via mitotic recombination. Molecular features and genetic evidence argue against a break-induced replication mechanism and instead support cross-over via double Holliday junction-based repair. This study provides a mechanistic understanding of mitotic recombination, an important mediator of LOH, and its effects on stem cells in vivo.
Collapse
Affiliation(s)
- Lara Al Zouabi
- Genetics and Developmental Biology Department, Institut Curie, PSL Research University, Sorbonne University, CNRS UMR 3215, INSERM U934, 75248 Paris, France
| | - Marine Stefanutti
- Genetics and Developmental Biology Department, Institut Curie, PSL Research University, Sorbonne University, CNRS UMR 3215, INSERM U934, 75248 Paris, France
| | - Spyridon Roumeliotis
- Genetics and Developmental Biology Department, Institut Curie, PSL Research University, Sorbonne University, CNRS UMR 3215, INSERM U934, 75248 Paris, France
| | - Gwenn Le Meur
- Genetics and Developmental Biology Department, Institut Curie, PSL Research University, Sorbonne University, CNRS UMR 3215, INSERM U934, 75248 Paris, France
| | - Benjamin Boumard
- Genetics and Developmental Biology Department, Institut Curie, PSL Research University, Sorbonne University, CNRS UMR 3215, INSERM U934, 75248 Paris, France
| | - Nick Riddiford
- Genetics and Developmental Biology Department, Institut Curie, PSL Research University, Sorbonne University, CNRS UMR 3215, INSERM U934, 75248 Paris, France
| | - Natalia Rubanova
- Genetics and Developmental Biology Department, Institut Curie, PSL Research University, Sorbonne University, CNRS UMR 3215, INSERM U934, 75248 Paris, France; Bioinformatics, Biostatistics, Epidemiology and Computational Systems Unit, Institut Curie, PSL Research University, INSERM U900, 75005 Paris, France
| | - Mylène Bohec
- ICGex Next-Generation Sequencing Platform, Institut Curie, PSL Research University, 75005 Paris, France
| | - Louis Gervais
- Genetics and Developmental Biology Department, Institut Curie, PSL Research University, Sorbonne University, CNRS UMR 3215, INSERM U934, 75248 Paris, France
| | - Nicolas Servant
- Bioinformatics, Biostatistics, Epidemiology and Computational Systems Unit, Institut Curie, PSL Research University, INSERM U900, 75005 Paris, France
| | - Allison J Bardin
- Genetics and Developmental Biology Department, Institut Curie, PSL Research University, Sorbonne University, CNRS UMR 3215, INSERM U934, 75248 Paris, France.
| |
Collapse
|
16
|
Showman S, Talbert PB, Xu Y, Adeyemi RO, Henikoff S. Expansion of human centromeric arrays in cells undergoing break-induced replication. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.11.566714. [PMID: 38014305 PMCID: PMC10680626 DOI: 10.1101/2023.11.11.566714] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Human centromeres are located within α-satellite arrays and evolve rapidly, which can lead to individual variation in array lengths. Proposed mechanisms for such alterations in lengths are unequal cross-over between sister chromatids, gene conversion, and break-induced replication. However, the underlying molecular mechanisms responsible for the massive, complex, and homogeneous organization of centromeric arrays have not been experimentally validated. Here, we use droplet digital PCR assays to demonstrate that centromeric arrays can expand and contract within ~20 somatic cell divisions of a cell line. We find that the frequency of array variation among single-cell-derived subclones ranges from a minimum of ~7% to a maximum of ~100%. Further clonal evolution revealed that centromere expansion is favored over contraction. We find that the homologous recombination protein RAD52 and the helicase PIF1 are required for extensive array change, suggesting that centromere sequence evolution can occur via break-induced replication.
Collapse
Affiliation(s)
- Soyeon Showman
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA, USA
- Molecular and Cellular Biology Graduate Program, University of Washington, Seattle, USA
- Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Paul B. Talbert
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA, USA
- Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Yiling Xu
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA, USA
- Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Richard O. Adeyemi
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA, USA
| | - Steven Henikoff
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA, USA
- Howard Hughes Medical Institute, Chevy Chase, MD, USA
| |
Collapse
|
17
|
Pannafino G, Chen JJ, Mithani V, Payero L, Gioia M, Brooks Crickard J, Alani E. The Dmc1 recombinase physically interacts with and promotes the meiotic crossover functions of the Mlh1-Mlh3 endonuclease. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.13.566911. [PMID: 38014100 PMCID: PMC10680668 DOI: 10.1101/2023.11.13.566911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
The accurate segregation of homologous chromosomes during the Meiosis I reductional division in most sexually reproducing eukaryotes requires crossing over between homologs. In baker's yeast approximately 80 percent of meiotic crossovers result from Mlh1-Mlh3 and Exo1 acting to resolve double-Holliday junction (dHJ) intermediates in a biased manner. Little is known about how Mlh1-Mlh3 is recruited to recombination intermediates and whether it interacts with other meiotic factors prior to its role in crossover resolution. We performed a haploinsufficiency screen in baker's yeast to identify novel genetic interactors with Mlh1-Mlh3 using sensitized mlh3 alleles that disrupt the stability of the Mlh1-Mlh3 complex and confer defects in mismatch repair but do not disrupt meiotic crossing over. We identified several genetic interactions between MLH3 and DMC1, the recombinase responsible for recombination between homologous chromosomes during meiosis. We then showed that Mlh3 physically interacts with Dmc1 in vitro and at times in meiotic prophase when Dmc1 acts as a recombinase. Interestingly, restricting MLH3 expression to roughly the time of crossover resolution resulted in a mlh3 null-like phenotype for crossing over. Our data are consistent with a model in which Dmc1 nucleates a polymer of Mlh1-Mlh3 to promote crossing over.
Collapse
Affiliation(s)
- Gianno Pannafino
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, USA 14853
| | - Jun Jie Chen
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, USA 14853
| | - Viraj Mithani
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, USA 14853
| | - Lisette Payero
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, USA 14853
| | - Michael Gioia
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, USA 14853
| | - J Brooks Crickard
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, USA 14853
| | - Eric Alani
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, USA 14853
| |
Collapse
|
18
|
Bhowmick R, Hickson ID, Liu Y. Completing genome replication outside of S phase. Mol Cell 2023; 83:3596-3607. [PMID: 37716351 DOI: 10.1016/j.molcel.2023.08.023] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Revised: 08/03/2023] [Accepted: 08/17/2023] [Indexed: 09/18/2023]
Abstract
Mitotic DNA synthesis (MiDAS) is an unusual form of DNA replication that occurs during mitosis. Initially, MiDAS was characterized as a process associated with intrinsically unstable loci known as common fragile sites that occurs after cells experience DNA replication stress (RS). However, it is now believed to be a more widespread "salvage" mechanism that is called upon to complete the duplication of any under-replicated genomic region. Emerging data suggest that MiDAS is a DNA repair process potentially involving two or more pathways working in parallel or sequentially. In this review, we introduce the causes of RS, regions of the human genome known to be especially vulnerable to RS, and the strategies used to complete DNA replication outside of S phase. Additionally, because MiDAS is a prominent feature of aneuploid cancer cells, we will discuss how targeting MiDAS might potentially lead to improvements in cancer therapy.
Collapse
Affiliation(s)
- Rahul Bhowmick
- Center for Chromosome Stability and Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, Panum Institute, Blegdamsvej 3B, 2200 Copenhagen N, Denmark; Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Ian D Hickson
- Center for Chromosome Stability and Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, Panum Institute, Blegdamsvej 3B, 2200 Copenhagen N, Denmark.
| | - Ying Liu
- Center for Chromosome Stability and Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, Panum Institute, Blegdamsvej 3B, 2200 Copenhagen N, Denmark.
| |
Collapse
|
19
|
Sato K, Knipscheer P. G-quadruplex resolution: From molecular mechanisms to physiological relevance. DNA Repair (Amst) 2023; 130:103552. [PMID: 37572578 DOI: 10.1016/j.dnarep.2023.103552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 07/29/2023] [Accepted: 08/01/2023] [Indexed: 08/14/2023]
Abstract
Guanine-rich DNA sequences can fold into stable four-stranded structures called G-quadruplexes or G4s. Research in the past decade demonstrated that G4 structures are widespread in the genome and prevalent in regulatory regions of actively transcribed genes. The formation of G4s has been tightly linked to important biological processes including regulation of gene expression and genome maintenance. However, they can also pose a serious threat to genome integrity especially by impeding DNA replication, and G4-associated somatic mutations have been found accumulated in the cancer genomes. Specialised DNA helicases and single stranded DNA binding proteins that can resolve G4 structures play a crucial role in preventing genome instability. The large variety of G4 unfolding proteins suggest the presence of multiple G4 resolution mechanisms in cells. Recently, there has been considerable progress in our detailed understanding of how G4s are resolved, especially during DNA replication. In this review, we first discuss the current knowledge of the genomic G4 landscapes and the impact of G4 structures on DNA replication and genome integrity. We then describe the recent progress on the mechanisms that resolve G4 structures and their physiological relevance. Finally, we discuss therapeutic opportunities to target G4 structures.
Collapse
Affiliation(s)
- Koichi Sato
- Oncode Institute, Hubrecht Institute-KNAW & University Medical Center Utrecht, Utrecht, the Netherlands.
| | - Puck Knipscheer
- Oncode Institute, Hubrecht Institute-KNAW & University Medical Center Utrecht, Utrecht, the Netherlands; Department of Human Genetics, Leiden University Medical Center, Leiden, the Netherlands.
| |
Collapse
|
20
|
Wang K, Hua X, Fu X, Hao Z, Jiao A, Li S. Petite Integration Factor 1 knockdown enhances gemcitabine sensitivity in pancreatic cancer cells via increasing DNA damage. J Appl Toxicol 2023; 43:1522-1532. [PMID: 37183367 DOI: 10.1002/jat.4494] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 04/18/2023] [Accepted: 05/03/2023] [Indexed: 05/16/2023]
Abstract
Chemoresistance is still a vital obstacle in various tumors chemotherapy. This study aimed to explore the role of Petite Integration Factor 1 (PIF1) in the sensitivity of gemcitabine response to pancreatic cancer cells. Gene Expression Profiling Interactive Analysis (GEPIA) database was employed for evaluating the level of PIF1 in pancreatic cancer tissues and normal tissues. The mRNA level of PIF1 was detected via reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis. The relative protein expression of PIF1, cleaved caspase-3, and phosphorylated histone H2Ax (γH2Ax) was assessed through western blot. Cell viability and apoptosis were assessed via Cell Counting Kit-8 (CCK-8) assay and flow cytometry, respectively. Moreover, lactate dehydrogenase (LDH) release and caspase-3 activity were determined via the corresponding LDH Cytotoxicity Assay Kit and caspase-3 colorimetric assay kit. PIF1 expression was upregulated in pancreatic cancer tissues and cells. Knockdown of PIF1 exhibited the repressive impact on the viability of AsPC-1 and PANC-1 cells. PIF1 knockdown enhanced LDH release and apoptosis in both AsPC-1 and PANC-1 cells. PIF1 downregulation could augment the sensitivity of gemcitabine in pancreatic cancer cells, as evidenced by lower cell viability and higher LDH release and apoptosis rate after knocking down PIF1 in gemcitabine-treated pancreatic cancer cells relative to pancreatic cancer cells treated with gemcitabine alone. Moreover, PIF1 knockdown increased γH2Ax protein expression and DNA damage, and gemcitabine treatment-induced DNA damage in AsPC-1 and PANC-1 cells was exacerbated by PIF1 silencing. Furthermore, gemcitabine treatment-caused increase of DNA damage was alleviated by PIF1 overexpression; whereas, this effect of PIF1 upregulation was reversed by thymidine, a DNA synthesis inhibitor. In addition, the decreased gemcitabine sensitivity response to pancreatic cancer cells caused by PIF1 upregulation was also hindered by thymidine treatment. In conclusion, PIF1 silencing enhanced gemcitabine sensitivity response to pancreatic cancer cells through aggrandizing DNA damage.
Collapse
Affiliation(s)
- Kun Wang
- Department of Hepatobiliary and Pancreatic Surgery, Liaoning Cancer Hospital & Institute, Cancer Hospital of China Medical University, Shenyang, Liaoning, China
| | - Xiangdong Hua
- Department of Hepatobiliary and Pancreatic Surgery, Liaoning Cancer Hospital & Institute, Cancer Hospital of China Medical University, Shenyang, Liaoning, China
| | - Xibo Fu
- Department of Hepatobiliary and Pancreatic Surgery, Liaoning Cancer Hospital & Institute, Cancer Hospital of China Medical University, Shenyang, Liaoning, China
| | - Zhiqiang Hao
- Department of Hepatobiliary and Pancreatic Surgery, Liaoning Cancer Hospital & Institute, Cancer Hospital of China Medical University, Shenyang, Liaoning, China
| | - Ao Jiao
- Department of Hepatobiliary and Pancreatic Surgery, Liaoning Cancer Hospital & Institute, Cancer Hospital of China Medical University, Shenyang, Liaoning, China
| | - Siyuan Li
- Department of Hepatobiliary and Pancreatic Surgery, Liaoning Cancer Hospital & Institute, Cancer Hospital of China Medical University, Shenyang, Liaoning, China
| |
Collapse
|
21
|
Chakraborty S, Schirmeisen K, Lambert SA. The multifaceted functions of homologous recombination in dealing with replication-associated DNA damages. DNA Repair (Amst) 2023; 129:103548. [PMID: 37541027 DOI: 10.1016/j.dnarep.2023.103548] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 07/26/2023] [Accepted: 07/27/2023] [Indexed: 08/06/2023]
Abstract
The perturbation of DNA replication, a phenomena termed "replication stress", is a driving force of genome instability and a hallmark of cancer cells. Among the DNA repair mechanisms that contribute to tolerating replication stress, the homologous recombination pathway is central to the alteration of replication fork progression. In many organisms, defects in the homologous recombination machinery result in increased cell sensitivity to replication-blocking agents and a higher risk of cancer in humans. Moreover, the status of homologous recombination in cancer cells often correlates with the efficacy of anti-cancer treatment. In this review, we discuss our current understanding of the different functions of homologous recombination in fixing replication-associated DNA damage and contributing to complete genome duplication. We also examine which functions are pivotal in preventing cancer and genome instability.
Collapse
Affiliation(s)
- Shrena Chakraborty
- Institut Curie, Université PSL, CNRS UMR3348, 91400 Orsay, France; Université Paris-Saclay, CNRS UMR3348, 91400 Orsay, France; Equipe Labelisée Ligue Nationale Contre le Cancer, France
| | - Kamila Schirmeisen
- Institut Curie, Université PSL, CNRS UMR3348, 91400 Orsay, France; Université Paris-Saclay, CNRS UMR3348, 91400 Orsay, France; Equipe Labelisée Ligue Nationale Contre le Cancer, France
| | - Sarah Ae Lambert
- Institut Curie, Université PSL, CNRS UMR3348, 91400 Orsay, France; Université Paris-Saclay, CNRS UMR3348, 91400 Orsay, France; Equipe Labelisée Ligue Nationale Contre le Cancer, France.
| |
Collapse
|
22
|
Zhai B, Zhang S, Li B, Zhang J, Yang X, Tan Y, Wang Y, Tan T, Yang X, Chen B, Tian Z, Cao Y, Huang Q, Gao J, Wang S, Zhang L. Dna2 removes toxic ssDNA-RPA filaments generated from meiotic recombination-associated DNA synthesis. Nucleic Acids Res 2023; 51:7914-7935. [PMID: 37351599 PMCID: PMC10450173 DOI: 10.1093/nar/gkad537] [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: 10/27/2022] [Revised: 06/01/2023] [Accepted: 06/09/2023] [Indexed: 06/24/2023] Open
Abstract
During the repair of DNA double-strand breaks (DSBs), de novo synthesized DNA strands can displace the parental strand to generate single-strand DNAs (ssDNAs). Many programmed DSBs and thus many ssDNAs occur during meiosis. However, it is unclear how these ssDNAs are removed for the complete repair of meiotic DSBs. Here, we show that meiosis-specific depletion of Dna2 (dna2-md) results in an abundant accumulation of RPA and an expansion of RPA from DSBs to broader regions in Saccharomyces cerevisiae. As a result, DSB repair is defective and spores are inviable, although the levels of crossovers/non-crossovers seem to be unaffected. Furthermore, Dna2 induction at pachytene is highly effective in removing accumulated RPA and restoring spore viability. Moreover, the depletion of Pif1, an activator of polymerase δ required for meiotic recombination-associated DNA synthesis, and Pif1 inhibitor Mlh2 decreases and increases RPA accumulation in dna2-md, respectively. In addition, blocking DNA synthesis during meiotic recombination dramatically decreases RPA accumulation in dna2-md. Together, our findings show that meiotic DSB repair requires Dna2 to remove ssDNA-RPA filaments generated from meiotic recombination-associated DNA synthesis. Additionally, we showed that Dna2 also regulates DSB-independent RPA distribution.
Collapse
Affiliation(s)
- Binyuan Zhai
- Center for Cell Structure and Function, Shandong Provincial Key Laboratory of Animal Resistance Biology, College of Life Sciences, Shandong Normal University, Jinan, Shandong 250014, China
| | - Shuxian Zhang
- Center for Reproductive Medicine, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Bo Li
- Shandong Provincial Key Laboratory of Animal Cell and Developmental Biology, School of Life Sciences, Shandong University, Qingdao, Shandong 266237, China
| | - Jiaming Zhang
- Center for Reproductive Medicine, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Xuan Yang
- Center for Reproductive Medicine, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Yingjin Tan
- Center for Reproductive Medicine, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Ying Wang
- Center for Cell Structure and Function, Shandong Provincial Key Laboratory of Animal Resistance Biology, College of Life Sciences, Shandong Normal University, Jinan, Shandong 250014, China
| | - Taicong Tan
- Center for Reproductive Medicine, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Xiao Yang
- Center for Reproductive Medicine, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
- National Research Center for Assisted Reproductive Technology and Reproductive Genetics, Shandong University, Jinan, Shandong 250012, China
- Key Laboratory of Reproductive Endocrinology of Ministry of Education, Jinan, Shandong 250001, China
- Shandong Provincial Clinical Research Center for Reproductive Health, Jinan, Shandong 250012, China
| | - Beiyi Chen
- Center for Reproductive Medicine, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
- Advanced Medical Research Institute, Shandong University, Jinan, Shandong 250012, China
| | - Zhongyu Tian
- Center for Reproductive Medicine, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
- Advanced Medical Research Institute, Shandong University, Jinan, Shandong 250012, China
| | - Yanding Cao
- Center for Reproductive Medicine, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
| | - Qilai Huang
- Shandong Provincial Key Laboratory of Animal Cell and Developmental Biology, School of Life Sciences, Shandong University, Qingdao, Shandong 266237, China
| | - Jinmin Gao
- Center for Cell Structure and Function, Shandong Provincial Key Laboratory of Animal Resistance Biology, College of Life Sciences, Shandong Normal University, Jinan, Shandong 250014, China
| | - Shunxin Wang
- Center for Reproductive Medicine, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250012, China
- National Research Center for Assisted Reproductive Technology and Reproductive Genetics, Shandong University, Jinan, Shandong 250012, China
- Key Laboratory of Reproductive Endocrinology of Ministry of Education, Jinan, Shandong 250001, China
- Shandong Provincial Clinical Research Center for Reproductive Health, Jinan, Shandong 250012, China
| | - Liangran Zhang
- Center for Cell Structure and Function, Shandong Provincial Key Laboratory of Animal Resistance Biology, College of Life Sciences, Shandong Normal University, Jinan, Shandong 250014, China
- Advanced Medical Research Institute, Shandong University, Jinan, Shandong 250012, China
| |
Collapse
|
23
|
Wang X, Zhang S, Zhang Z, Mazloum NA, Lee EYC, Lee MYW. The DHX9 helicase interacts with human DNA polymerase δ4 and stimulates its activity in D-loop extension synthesis. DNA Repair (Amst) 2023; 128:103513. [PMID: 37285751 PMCID: PMC10330758 DOI: 10.1016/j.dnarep.2023.103513] [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: 03/08/2023] [Revised: 04/28/2023] [Accepted: 05/11/2023] [Indexed: 06/09/2023]
Abstract
The extension of the invading strand within a displacement loop (D-loop) is a key step in homology directed repair (HDR) of doubled stranded DNA breaks. The primary goal of these studies was to test the hypotheses that 1) D-loop extension by human DNA polymerase δ4 (Pol δ4) is facilitated by DHX9, a 3' to 5' motor helicase, which acts to unwind the leading edge of the D-loop, and 2) the recruitment of DHX9 is mediated by direct protein-protein interactions between DHX9 and Pol δ4 and/or PCNA. DNA synthesis by Pol δ4 was analyzed in a reconstitution assay by the extension of a 93mer oligonucleotide inserted into a plasmid to form a D-loop. Product formation by Pol δ4 was monitored by incorporation of [α-32P]dNTPs into the 93mer primer followed by denaturing gel electrophoresis. The results showed that DHX9 strongly stimulated Pol δ4 mediated D-loop extension. Direct interactions of DHX9 with PCNA, the p125 and the p12 subunits of Pol δ4 were demonstrated by pull-down assays with purified proteins. These data support the hypothesis that DHX9 helicase is recruited by Pol δ4/PCNA to facilitate D-loop synthesis in HDR, and is a participant in cellular HDR. The involvement of DHX9 in HDR represents an important addition to its multiple cellular roles. Such helicase-polymerase interactions may represent an important aspect of the mechanisms involved in D-loop primer extension synthesis in HDR.
Collapse
Affiliation(s)
- Xiaoxiao Wang
- Department of Biochemistry and Molecular Biology, New York Medical College, 15 Dana Road, Valhalla, NY 10595, USA
| | - Sufang Zhang
- Department of Biochemistry and Molecular Biology, New York Medical College, 15 Dana Road, Valhalla, NY 10595, USA
| | - Zhongtao Zhang
- Department of Biochemistry and Molecular Biology, New York Medical College, 15 Dana Road, Valhalla, NY 10595, USA
| | - Nayef A Mazloum
- Department of Biochemistry and Molecular Biology, New York Medical College, 15 Dana Road, Valhalla, NY 10595, USA
| | - Ernest Y C Lee
- Department of Biochemistry and Molecular Biology, New York Medical College, 15 Dana Road, Valhalla, NY 10595, USA
| | - Marietta Y W Lee
- Department of Biochemistry and Molecular Biology, New York Medical College, 15 Dana Road, Valhalla, NY 10595, USA.
| |
Collapse
|
24
|
Lee RS, Geronimo CL, Liu L, Twarowski JM, Malkova A, Zakian VA. Identification of the nuclear localization signal in the Saccharomyces cerevisiae Pif1 DNA helicase. PLoS Genet 2023; 19:e1010853. [PMID: 37486934 PMCID: PMC10399864 DOI: 10.1371/journal.pgen.1010853] [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: 04/23/2023] [Revised: 08/03/2023] [Accepted: 07/02/2023] [Indexed: 07/26/2023] Open
Abstract
Saccharomyces cerevisiae Pif1 is a multi-functional DNA helicase that plays diverse roles in the maintenance of the nuclear and mitochondrial genomes. Two isoforms of Pif1 are generated from a single open reading frame by the use of alternative translational start sites. The Mitochondrial Targeting Signal (MTS) of Pif1 is located between the two start sites, but a Nuclear Localization Signal (NLS) has not been identified. Here we used sequence and functional analysis to identify an NLS element. A mutant allele of PIF1 (pif1-NLSΔ) that lacks four basic amino acids (781KKRK784) in the carboxyl-terminal domain of the 859 amino acid Pif1 was expressed at wild type levels and retained wild type mitochondrial function. However, pif1-NLSΔ cells were defective in four tests for nuclear function: telomere length maintenance, Okazaki fragment processing, break-induced replication (BIR), and binding to nuclear target sites. Fusing the NLS from the simian virus 40 (SV40) T-antigen to the Pif1-NLSΔ protein reduced the nuclear defects of pif1-NLSΔ cells. Thus, four basic amino acids near the carboxyl end of Pif1 are required for the vast majority of nuclear Pif1 function. Our study also reveals phenotypic differences between the previously described loss of function pif1-m2 allele and three other pif1 mutant alleles generated in this work, which will be useful to study nuclear Pif1 functions.
Collapse
Affiliation(s)
- Rosemary S. Lee
- Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Carly L. Geronimo
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, United States of America
| | - Liping Liu
- Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Jerzy M. Twarowski
- Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Anna Malkova
- Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Virginia A. Zakian
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, United States of America
| |
Collapse
|
25
|
Gan X, Zhang Y, Jiang D, Shi J, Zhao H, Xie C, Wang Y, Xu J, Zhang X, Cai G, Wang H, Huang J, Chen X. Proper RPA acetylation promotes accurate DNA replication and repair. Nucleic Acids Res 2023; 51:5565-5583. [PMID: 37140030 PMCID: PMC10287905 DOI: 10.1093/nar/gkad291] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2023] [Revised: 04/06/2023] [Accepted: 04/12/2023] [Indexed: 05/05/2023] Open
Abstract
The single-stranded DNA (ssDNA) binding protein complex RPA plays a critical role in promoting DNA replication and multiple DNA repair pathways. However, how RPA is regulated to achieve its functions precisely in these processes remains elusive. Here, we found that proper acetylation and deacetylation of RPA are required to regulate RPA function in promoting high-fidelity DNA replication and repair. We show that yeast RPA is acetylated on multiple conserved lysines by the acetyltransferase NuA4 upon DNA damage. Mimicking constitutive RPA acetylation or blocking its acetylation causes spontaneous mutations with the signature of micro-homology-mediated large deletions or insertions. In parallel, improper RPA acetylation/deacetylation impairs DNA double-strand break (DSB) repair by the accurate gene conversion or break-induced replication while increasing the error-prone repair by single-strand annealing or alternative end joining. Mechanistically, we show that proper acetylation and deacetylation of RPA ensure its normal nuclear localization and ssDNA binding ability. Importantly, mutation of the equivalent residues in human RPA1 also impairs RPA binding on ssDNA, leading to attenuated RAD51 loading and homologous recombination repair. Thus, timely RPA acetylation and deacetylation likely represent a conserved mechanism promoting high-fidelity replication and repair while discriminating the error-prone repair mechanisms in eukaryotes.
Collapse
Affiliation(s)
- Xiaoli Gan
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Wuhan University, Wuhan, Hubei 430072, China
| | - Yueyue Zhang
- The First Affiliated Hospital of USTC, MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230001, China
| | - Donghao Jiang
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Wuhan University, Wuhan, Hubei 430072, China
| | - Jingyao Shi
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Wuhan University, Wuhan, Hubei 430072, China
| | - Han Zhao
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Wuhan University, Wuhan, Hubei 430072, China
| | - Chengyu Xie
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Wuhan University, Wuhan, Hubei 430072, China
| | - Yanyan Wang
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Wuhan University, Wuhan, Hubei 430072, China
| | - Jingyan Xu
- Department of Hematology, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, Nanjing, China
| | - Xinghua Zhang
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Wuhan University, Wuhan, Hubei 430072, China
| | - Gang Cai
- The First Affiliated Hospital of USTC, MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230001, China
| | - Hailong Wang
- Beijing Key Laboratory of DNA Damage Response and College of Life Sciences, Capital Normal University, Beijing 100048, China
| | - Jun Huang
- The MOE Key Laboratory of Biosystems Homeostasis & Protection, Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology and Innovation Center for Cell Signaling Network, Life Sciences Institute, Zhejiang University, Hangzhou 310058, China
| | - Xuefeng Chen
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Centre of Immunology and Metabolism, Wuhan University, Wuhan, Hubei 430072, China
| |
Collapse
|
26
|
Mustafi M, Kwon Y, Sung P, Greene EC. Single-molecule visualization of Pif1 helicase translocation on single-stranded DNA. J Biol Chem 2023; 299:104817. [PMID: 37178921 PMCID: PMC10279920 DOI: 10.1016/j.jbc.2023.104817] [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: 02/28/2023] [Revised: 04/22/2023] [Accepted: 04/23/2023] [Indexed: 05/15/2023] Open
Abstract
Pif1 is a broadly conserved helicase that is essential for genome integrity and participates in numerous aspects of DNA metabolism, including telomere length regulation, Okazaki fragment maturation, replication fork progression through difficult-to-replicate sites, replication fork convergence, and break-induced replication. However, details of its translocation properties and the importance of amino acids residues implicated in DNA binding remain unclear. Here, we use total internal reflection fluorescence microscopy with single-molecule DNA curtain assays to directly observe the movement of fluorescently tagged Saccharomyces cerevisiae Pif1 on single-stranded DNA (ssDNA) substrates. We find that Pif1 binds tightly to ssDNA and translocates very rapidly (∼350 nucleotides per second) in the 5'→3' direction over relatively long distances (∼29,500 nucleotides). Surprisingly, we show the ssDNA-binding protein replication protein A inhibits Pif1 activity in both bulk biochemical and single-molecule measurements. However, we demonstrate Pif1 can strip replication protein A from ssDNA, allowing subsequent molecules of Pif1 to translocate unimpeded. We also assess the functional attributes of several Pif1 mutations predicted to impair contact with the ssDNA substrate. Taken together, our findings highlight the functional importance of these amino acid residues in coordinating the movement of Pif1 along ssDNA.
Collapse
Affiliation(s)
- Mainak Mustafi
- Department of Biochemistry & Molecular Biophysics, Columbia University, New York, New York, USA
| | - Youngho Kwon
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, Texas, USA
| | - Patrick Sung
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, Texas, USA
| | - Eric C Greene
- Department of Biochemistry & Molecular Biophysics, Columbia University, New York, New York, USA.
| |
Collapse
|
27
|
Cahill T, da Silveira WA, Renaud L, Wang H, Williamson T, Chung D, Chan S, Overton I, Hardiman G. Investigating the effects of chronic low-dose radiation exposure in the liver of a hypothermic zebrafish model. Sci Rep 2023; 13:918. [PMID: 36650199 PMCID: PMC9845366 DOI: 10.1038/s41598-022-26976-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Accepted: 12/22/2022] [Indexed: 01/18/2023] Open
Abstract
Mankind's quest for a manned mission to Mars is placing increased emphasis on the development of innovative radio-protective countermeasures for long-term space travel. Hibernation confers radio-protective effects in hibernating animals, and this has led to the investigation of synthetic torpor to mitigate the deleterious effects of chronic low-dose-rate radiation exposure. Here we describe an induced torpor model we developed using the zebrafish. We explored the effects of radiation exposure on this model with a focus on the liver. Transcriptomic and behavioural analyses were performed. Radiation exposure resulted in transcriptomic perturbations in lipid metabolism and absorption, wound healing, immune response, and fibrogenic pathways. Induced torpor reduced metabolism and increased pro-survival, anti-apoptotic, and DNA repair pathways. Coupled with radiation exposure, induced torpor led to a stress response but also revealed maintenance of DNA repair mechanisms, pro-survival and anti-apoptotic signals. To further characterise our model of induced torpor, the zebrafish model was compared with hepatic transcriptomic data from hibernating grizzly bears (Ursus arctos horribilis) and active controls revealing conserved responses in gene expression associated with anti-apoptotic processes, DNA damage repair, cell survival, proliferation, and antioxidant response. Similarly, the radiation group was compared with space-flown mice revealing shared changes in lipid metabolism.
Collapse
Affiliation(s)
- Thomas Cahill
- School of Biological Sciences and Institute for Global Food Security, Queens University Belfast, Belfast, BT9 5DL, UK
| | - Willian Abraham da Silveira
- School of Health, Science and Wellbeing, Department of Biological Sciences, Science Centre, Staffordshire University, Leek Road, Stoke-On-Trent, ST4 2DF, UK
- International Space University, 1 Rue Jean-Dominique Cassini, 67400, Illkirch-Graffenstaden, France
| | - Ludivine Renaud
- Department of Medicine, Medical University of South Carolina, Charleston, SC, 29425, USA
| | - Hao Wang
- School of Biological Sciences and Institute for Global Food Security, Queens University Belfast, Belfast, BT9 5DL, UK
| | - Tucker Williamson
- Department of Drug Discovery and Biomedical Sciences, Medical University of South Carolina, Charleston, SC, 29425, USA
| | - Dongjun Chung
- Department of Biomedical Informatics, The Ohio State University, Columbus, OH, 43210, USA
| | - Sherine Chan
- Department of Drug Discovery and Biomedical Sciences, Medical University of South Carolina, Charleston, SC, 29425, USA
- JLABS at the Children's National Research and Innovation Campus, Washington, DC, 20012, USA
| | - Ian Overton
- Patrick G Johnston Centre for Cancer Research, Queen's University Belfast, Belfast, BT9 7AE, UK
| | - Gary Hardiman
- School of Biological Sciences and Institute for Global Food Security, Queens University Belfast, Belfast, BT9 5DL, UK.
- Department of Medicine, Medical University of South Carolina, Charleston, SC, 29425, USA.
| |
Collapse
|
28
|
Cai T, Wang N, Meng P, Sun W, Cui Y. Up-regulated PIF1 predicts poor clinical outcomes and correlates with low immune infiltrates in clear cell renal cell carcinoma. Front Genet 2023; 13:1058040. [PMID: 36685888 PMCID: PMC9847676 DOI: 10.3389/fgene.2022.1058040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 12/08/2022] [Indexed: 01/06/2023] Open
Abstract
Background: Petite Integration Factor 1 (PIF1) is a multifunctional helicase and DNA processing enzyme that plays an important role in the process of several cancer types. However, the relationship between clear cell renal cell carcinoma (ccRCC) and PIF1 remains unclear. This study aims to explore the role of PIF1 in ccRCC tumorigenesis and prognosis. Methods: Based on The Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus (GEO) database, we retrieved and verified the expression of PIF1 in ccRCC tissues as well as normal tissues. To assess the protein expression of PIF1 by using the Human Protein Atlas and the Clinical Proteomic Tumor Analysis Consortium (CPTAC). We also performed receiver operating characteristic (ROC) curve analysis to differentiate the effectiveness of PIF1 in ccRCC and adjacent normal tissues. To evaluate the value of PIF1 on clinical outcomes in ccRCC patients by using multivariate methods and Kaplan‒Meier survival curves. Protein‒protein interaction (PPI) networks were made with STRING. We determined the relationship between the expression of PIF1 and immune cell infiltration with single-sample gene set enrichment analysis (ssGSEA). Results: Compared with normal tissues, the expression of PIF1 was significantly elevated in ccRCC. The mRNA expression of PIF1 is correlated with high TNM stage and high pathologic stage. The receiver operating characteristic (ROC) curve analysis showed that PIF1 was related to an area under the curve (AUC) value of 0.928 to distinguish between ccRCC tissues and normal tissues. Kaplan‒Meier survival analysis showed that the overall survival (OS) of ccRCC patients with a high level of PIF1 was significantly shorter than that of those with a low level of PIF1. PIF1 may play an important role in the occurrence of tumors. Correlation analysis showed that PIF1-mediated carcinogenesis may participate in the process of tumor immune escape in ccRCC. Conclusion: PIF1 could be a reference biomarker to identify ccRCC patients with poor prognosis. PIF1 may play a distinct role in the microenvironment of ccRCC by regulating tumor infiltration of immune cells, which is a new therapeutic target to affect the growth of the tumor.
Collapse
Affiliation(s)
- Tong Cai
- Department of Urology, The Affiliated Hospital of Yangzhou University, Yangzhou University, Yangzhou, Jiangsu, China
| | - Ning Wang
- Department of Urology, The Affiliated YantaiYuhuangding Hospital of Qingdao University, Yantai, Shandong, China
| | - Peng Meng
- Department of Oncology, Yantai Traditional Chinese Medicine Hospital, Yantai, Shandong, China
| | - Weigui Sun
- Department of Urology, The Affiliated Hospital of Yangzhou University, Yangzhou University, Yangzhou, Jiangsu, China,*Correspondence: Weigui Sun, ; Yuanshan Cui,
| | - Yuanshan Cui
- Department of Urology, The Affiliated YantaiYuhuangding Hospital of Qingdao University, Yantai, Shandong, China,*Correspondence: Weigui Sun, ; Yuanshan Cui,
| |
Collapse
|
29
|
Ziesel A, Weng Q, Ahuja JS, Bhattacharya A, Dutta R, Cheng E, Börner GV, Lichten M, Hollingsworth NM. Rad51-mediated interhomolog recombination during budding yeast meiosis is promoted by the meiotic recombination checkpoint and the conserved Pif1 helicase. PLoS Genet 2022; 18:e1010407. [PMID: 36508468 PMCID: PMC9779700 DOI: 10.1371/journal.pgen.1010407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Revised: 12/22/2022] [Accepted: 11/16/2022] [Indexed: 12/14/2022] Open
Abstract
During meiosis, recombination between homologous chromosomes (homologs) generates crossovers that promote proper segregation at the first meiotic division. Recombination is initiated by Spo11-catalyzed DNA double strand breaks (DSBs). 5' end resection of the DSBs creates 3' single strand tails that two recombinases, Rad51 and Dmc1, bind to form presynaptic filaments that search for homology, mediate strand invasion and generate displacement loops (D-loops). D-loop processing then forms crossover and non-crossover recombinants. Meiotic recombination occurs in two temporally distinct phases. During Phase 1, Rad51 is inhibited and Dmc1 mediates the interhomolog recombination that promotes homolog synapsis. In Phase 2, Rad51 becomes active and functions with Rad54 to repair residual DSBs, making increasing use of sister chromatids. The transition from Phase 1 to Phase 2 is controlled by the meiotic recombination checkpoint through the meiosis-specific effector kinase Mek1. This work shows that constitutive activation of Rad51 in Phase 1 results in a subset of DSBs being repaired by a Rad51-mediated interhomolog recombination pathway that is distinct from that of Dmc1. Strand invasion intermediates generated by Rad51 require more time to be processed into recombinants, resulting in a meiotic recombination checkpoint delay in prophase I. Without the checkpoint, Rad51-generated intermediates are more likely to involve a sister chromatid, thereby increasing Meiosis I chromosome nondisjunction. This Rad51 interhomolog recombination pathway is specifically promoted by the conserved 5'-3' helicase PIF1 and its paralog, RRM3 and requires Pif1 helicase activity and its interaction with PCNA. This work demonstrates that (1) inhibition of Rad51 during Phase 1 is important to prevent competition with Dmc1 for DSB repair, (2) Rad51-mediated meiotic recombination intermediates are initially processed differently than those made by Dmc1, and (3) the meiotic recombination checkpoint provides time during prophase 1 for processing of Rad51-generated recombination intermediates.
Collapse
Affiliation(s)
- Andrew Ziesel
- Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, United States of America
| | - Qixuan Weng
- Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, United States of America
| | - Jasvinder S. Ahuja
- Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America
| | - Abhishek Bhattacharya
- Center for Gene Regulation in Health and Disease and Department of Biological, Geological and Environmental Sciences, Cleveland State University, Cleveland, Ohio, United States of America
| | - Raunak Dutta
- Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, United States of America
| | - Evan Cheng
- Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, United States of America
| | - G. Valentin Börner
- Center for Gene Regulation in Health and Disease and Department of Biological, Geological and Environmental Sciences, Cleveland State University, Cleveland, Ohio, United States of America
| | - Michael Lichten
- Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America
| | - Nancy M. Hollingsworth
- Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, United States of America
| |
Collapse
|
30
|
Yadav T, Zhang JM, Ouyang J, Leung W, Simoneau A, Zou L. TERRA and RAD51AP1 promote alternative lengthening of telomeres through an R- to D-loop switch. Mol Cell 2022; 82:3985-4000.e4. [PMID: 36265486 PMCID: PMC9637728 DOI: 10.1016/j.molcel.2022.09.026] [Citation(s) in RCA: 38] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 08/08/2022] [Accepted: 09/23/2022] [Indexed: 11/05/2022]
Abstract
Alternative lengthening of telomeres (ALT), a telomerase-independent process maintaining telomeres, is mediated by break-induced replication (BIR). RAD52 promotes ALT by facilitating D-loop formation, but ALT also occurs through a RAD52-independent BIR pathway. Here, we show that the telomere non-coding RNA TERRA forms dynamic telomeric R-loops and contributes to ALT activity in RAD52 knockout cells. TERRA forms R-loops in vitro and at telomeres in a RAD51AP1-dependent manner. The formation of R-loops by TERRA increases G-quadruplexes (G4s) at telomeres. G4 stabilization enhances ALT even when TERRA is depleted, suggesting that G4s act downstream of R-loops to promote BIR. In vitro, the telomeric R-loops assembled by TERRA and RAD51AP1 generate G4s, which persist after R-loop resolution and allow formation of telomeric D-loops without RAD52. Thus, the dynamic telomeric R-loops formed by TERRA and RAD51AP1 enable the RAD52-independent ALT pathway, and G4s orchestrate an R- to D-loop switch at telomeres to stimulate BIR.
Collapse
Affiliation(s)
- Tribhuwan Yadav
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Jia-Min Zhang
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Jian Ouyang
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Wendy Leung
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Antoine Simoneau
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Lee Zou
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA; Department of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
| |
Collapse
|
31
|
Kloeber JA, Lou Z. Critical DNA damaging pathways in tumorigenesis. Semin Cancer Biol 2022; 85:164-184. [PMID: 33905873 PMCID: PMC8542061 DOI: 10.1016/j.semcancer.2021.04.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2021] [Revised: 04/13/2021] [Accepted: 04/15/2021] [Indexed: 12/22/2022]
Abstract
The acquisition of DNA damage is an early driving event in tumorigenesis. Premalignant lesions show activated DNA damage responses and inactivation of DNA damage checkpoints promotes malignant transformation. However, DNA damage is also a targetable vulnerability in cancer cells. This requires a detailed understanding of the cellular and molecular mechanisms governing DNA integrity. Here, we review current work on DNA damage in tumorigenesis. We discuss DNA double strand break repair, how repair pathways contribute to tumorigenesis, and how double strand breaks are linked to the tumor microenvironment. Next, we discuss the role of oncogenes in promoting DNA damage through replication stress. Finally, we discuss our current understanding on DNA damage in micronuclei and discuss therapies targeting these DNA damage pathways.
Collapse
Affiliation(s)
- Jake A Kloeber
- Department of Oncology, Mayo Clinic, Rochester, MN, 55905, USA; Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN, 55905, USA; Mayo Clinic Medical Scientist Training Program, Mayo Clinic, Rochester, MN, 55905, USA
| | - Zhenkun Lou
- Department of Oncology, Mayo Clinic, Rochester, MN, 55905, USA.
| |
Collapse
|
32
|
Keymakh M, Dau J, Hu J, Ferlez B, Lisby M, Crickard JB. Rdh54 stabilizes Rad51 at displacement loop intermediates to regulate genetic exchange between chromosomes. PLoS Genet 2022; 18:e1010412. [PMID: 36099310 PMCID: PMC9506641 DOI: 10.1371/journal.pgen.1010412] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 09/23/2022] [Accepted: 09/04/2022] [Indexed: 11/20/2022] Open
Abstract
Homologous recombination (HR) is a double-strand break DNA repair pathway that preserves chromosome structure. To repair damaged DNA, HR uses an intact donor DNA sequence located elsewhere in the genome. After the double-strand break is repaired, DNA sequence information can be transferred between donor and recipient DNA molecules through different mechanisms, including DNA crossovers that form between homologous chromosomes. Regulation of DNA sequence transfer is an important step in effectively completing HR and maintaining genome integrity. For example, mitotic exchange of information between homologous chromosomes can result in loss-of-heterozygosity (LOH), and in higher eukaryotes, the development of cancer. The DNA motor protein Rdh54 is a highly conserved DNA translocase that functions during HR. Several existing phenotypes in rdh54Δ strains suggest that Rdh54 may regulate effective exchange of DNA during HR. In our current study, we used a combination of biochemical and genetic techniques to dissect the role of Rdh54 on the exchange of genetic information during DNA repair. Our data indicate that RDH54 regulates DNA strand exchange by stabilizing Rad51 at an early HR intermediate called the displacement loop (D-loop). Rdh54 acts in opposition to Rad51 removal by the DNA motor protein Rad54. Furthermore, we find that expression of a catalytically inactivate allele of Rdh54, rdh54K318R, favors non-crossover outcomes. From these results, we propose a model for how Rdh54 may kinetically regulate strand exchange during homologous recombination. Homologous recombination is an important pathway in repairing DNA double strand breaks. For the purposes of this study, HR can be divided into two stages. The first is a DNA repair stage in which the broken DNA molecule is fixed. In the second stage, information can move from one DNA molecule to another. Enzymes that use the power of ATP hydrolysis to move along dsDNA aid in regulating both stages of HR. In this work we focused on the understudied DNA motor protein Rdh54. We combined genetic and biochemical approaches to show that Rdh54 regulates HR by stabilizing the recombinase protein Rad51 at early HR intermediates.
Collapse
Affiliation(s)
- Margaret Keymakh
- Deparment of Molecular Biology and Genetics, Cornell University Ithaca, Ithaca, New York, United States of America
| | - Jennifer Dau
- Deparment of Molecular Biology and Genetics, Cornell University Ithaca, Ithaca, New York, United States of America
| | - Jingyi Hu
- Deparment of Molecular Biology and Genetics, Cornell University Ithaca, Ithaca, New York, United States of America
| | - Bryan Ferlez
- Deparment of Molecular Biology and Genetics, Cornell University Ithaca, Ithaca, New York, United States of America
| | - Michael Lisby
- Department of Biology, University of Copenhagen, Copenhagen N, Denmark
| | - J. Brooks Crickard
- Deparment of Molecular Biology and Genetics, Cornell University Ithaca, Ithaca, New York, United States of America
- * E-mail:
| |
Collapse
|
33
|
Zhou X, Pan Y, Qu Y, Ke X. Tideglusib Inhibits Pif1 Helicase of Bacteroides sp. via an Irreversible and Cys-380-Dependent Mechanism. ACS OMEGA 2022; 7:31289-31298. [PMID: 36092604 PMCID: PMC9453980 DOI: 10.1021/acsomega.2c03546] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Accepted: 08/15/2022] [Indexed: 06/15/2023]
Abstract
Pif1 helicase plays multiple roles in maintaining genome stability, which is an attractive therapeutic target for helicase-related diseases, while small molecules targeting Pif1 are not yet available. In this study, we performed a fluorescence polarization-based high-throughput screening and identified that an FDA-approved drug, Tideglusib (TD), could inhibit the DNA-binding activity (IC50 = 6.2 ± 0.4 μM) and ATPase and helicase activity (IC50 = 2-4 μM) of Bacteroides sp. Pif1 (BaPif1), which was also confirmed with human Pif1. In addition, the TD analogue TDZD-8 displayed similar inhibitory effects on Pif1 activities. Notably, TD irreversibly inhibited BaPif1 and severely induced BaPif1 aggregation. Furthermore, inhibition of BaPif1 by TD was significantly attenuated in the presence of dithiothreitol, indicating that TD could be a thiol-reactive compound. We also identified that Cys-380 of BaPif1 is critical for the inhibition by TD, suggesting that TD inhibits BaPif1 via an irreversible and Cys-380-dependent mechanism.
Collapse
|
34
|
Shaw AE, Kairamkonda S, Ghodke H, Schauer GD. Biochemical and single-molecule techniques to study accessory helicase resolution of R-loop proteins at stalled replication forks. Methods Enzymol 2022; 673:191-225. [PMID: 35965008 DOI: 10.1016/bs.mie.2022.03.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
R-loop proteins present a stable and robust blockade to the progression of a DNA replication fork during S-phase. The consequences of this block can include mutagenesis and other irreversible chromosomal catastrophes, causing genomic instability and disease. As such, further investigation into the molecular mechanisms underlying R-loop protein resolution is warranted. The critical role of non-replicative accessory helicases in R-loop protein resolution has increasingly come into light in recent years. Such helicases include the Pif1-family, monomeric helicases that have been studied in many different contexts and that have been ascribed to a multitude of separable protective functions in the cell. In this chapter, we present protocols to study R-loop protein resolution by Pif1 helicase at stalled replication forks using purified proteins, both at the biochemical and single-molecule level. Our system uses recombinant proteins expressed in Saccharomyces cerevisiae but could apply to practically any organism of interest due to the high interspecies homology of the proteins involved in DNA replication. The methods we outline are extensible to many systems and should be applicable to studying R-loop clearance by any Superfamily (SF) 1B helicase. These techniques will further enable mechanistic research on these critical but understudied components of the genomic maintenance program.
Collapse
Affiliation(s)
- Alisa E Shaw
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, United States
| | - Sreeya Kairamkonda
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, United States
| | - Harshad Ghodke
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW, Australia; Illawarra Health & Medical Research Institute, Wollongong, NSW, Australia
| | - Grant D Schauer
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, United States.
| |
Collapse
|
35
|
Kohzaki M. Mammalian Resilience Revealed by a Comparison of Human Diseases and Mouse Models Associated With DNA Helicase Deficiencies. Front Mol Biosci 2022; 9:934042. [PMID: 36032672 PMCID: PMC9403131 DOI: 10.3389/fmolb.2022.934042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Accepted: 06/23/2022] [Indexed: 12/01/2022] Open
Abstract
Maintaining genomic integrity is critical for sustaining individual animals and passing on the genome to subsequent generations. Several enzymes, such as DNA helicases and DNA polymerases, are involved in maintaining genomic integrity by unwinding and synthesizing the genome, respectively. Indeed, several human diseases that arise caused by deficiencies in these enzymes have long been known. In this review, the author presents the DNA helicases associated with human diseases discovered to date using recent analyses, including exome sequences. Since several mouse models that reflect these human diseases have been developed and reported, this study also summarizes the current knowledge regarding the outcomes of DNA helicase deficiencies in humans and mice and discusses possible mechanisms by which DNA helicases maintain genomic integrity in mammals. It also highlights specific diseases that demonstrate mammalian resilience, in which, despite the presence of genomic instability, patients and mouse models have lifespans comparable to those of the general population if they do not develop cancers; finally, this study discusses future directions for therapeutic applications in humans that can be explored using these mouse models.
Collapse
|
36
|
Mellor C, Perez C, Sale JE. Creation and resolution of non-B-DNA structural impediments during replication. Crit Rev Biochem Mol Biol 2022; 57:412-442. [PMID: 36170051 PMCID: PMC7613824 DOI: 10.1080/10409238.2022.2121803] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2022] [Revised: 08/02/2022] [Accepted: 08/25/2022] [Indexed: 01/27/2023]
Abstract
During replication, folding of the DNA template into non-B-form secondary structures provides one of the most abundant impediments to the smooth progression of the replisome. The core replisome collaborates with multiple accessory factors to ensure timely and accurate duplication of the genome and epigenome. Here, we discuss the forces that drive non-B structure formation and the evidence that secondary structures are a significant and frequent source of replication stress that must be actively countered. Taking advantage of recent advances in the molecular and structural biology of the yeast and human replisomes, we examine how structures form and how they may be sensed and resolved during replication.
Collapse
Affiliation(s)
- Christopher Mellor
- Division of Protein & Nucleic Acid Chemistry, MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Consuelo Perez
- Division of Protein & Nucleic Acid Chemistry, MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Julian E Sale
- Division of Protein & Nucleic Acid Chemistry, MRC Laboratory of Molecular Biology, Cambridge, UK
| |
Collapse
|
37
|
Casas-Delucchi CS, Daza-Martin M, Williams SL, Coster G. The mechanism of replication stalling and recovery within repetitive DNA. Nat Commun 2022; 13:3953. [PMID: 35853874 PMCID: PMC9296464 DOI: 10.1038/s41467-022-31657-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Accepted: 06/27/2022] [Indexed: 11/09/2022] Open
Abstract
Accurate chromosomal DNA replication is essential to maintain genomic stability. Genetic evidence suggests that certain repetitive sequences impair replication, yet the underlying mechanism is poorly defined. Replication could be directly inhibited by the DNA template or indirectly, for example by DNA-bound proteins. Here, we reconstitute replication of mono-, di- and trinucleotide repeats in vitro using eukaryotic replisomes assembled from purified proteins. We find that structure-prone repeats are sufficient to impair replication. Whilst template unwinding is unaffected, leading strand synthesis is inhibited, leading to fork uncoupling. Synthesis through hairpin-forming repeats is rescued by replisome-intrinsic mechanisms, whereas synthesis of quadruplex-forming repeats requires an extrinsic accessory helicase. DNA-induced fork stalling is mechanistically similar to that induced by leading strand DNA lesions, highlighting structure-prone repeats as an important potential source of replication stress. Thus, we propose that our understanding of the cellular response to replication stress may also be applied to DNA-induced replication stalling.
Collapse
Affiliation(s)
- Corella S Casas-Delucchi
- Genome Replication lab, Division of Cancer Biology, Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London, SW3 6JB, UK
| | - Manuel Daza-Martin
- Genome Replication lab, Division of Cancer Biology, Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London, SW3 6JB, UK
| | - Sophie L Williams
- Genome Replication lab, Division of Cancer Biology, Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London, SW3 6JB, UK
| | - Gideon Coster
- Genome Replication lab, Division of Cancer Biology, Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London, SW3 6JB, UK.
| |
Collapse
|
38
|
Firlej M, Weir JR. Unwinding during stressful times: Mechanisms of helicases in meiotic recombination. Curr Top Dev Biol 2022; 151:191-215. [PMID: 36681470 DOI: 10.1016/bs.ctdb.2022.06.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Successful meiosis I requires that homologous chromosomes be correctly linked before they are segregated. In most organisms this physical linkage is achieved through the generation of crossovers between the homologs. Meiotic recombination co-opts and modifies the canonical homologous recombination pathway to successfully generate crossovers One of the central components of this pathway are a number of conserved DNA helicases. Helicases couple nucleic acid binding to nucleotide hydrolysis and use this activity to modify DNA or protein-DNA substrates. During meiosis I it is necessary for the cell to modulate the canonical DNA repair pathways in order to facilitate the generation of interhomolog crossovers. Many of these meiotic modulations take place in pathways involving DNA helicases, or with a meiosis specific helicase. This short review explores what is currently understood about these helicases, their interaction partners, and the role of regulatory modifications during meiosis I. We focus in particular on the molecular structure and mechanisms of these helicases.
Collapse
Affiliation(s)
- Magdalena Firlej
- Structural Biochemistry of Meiosis Group, Friedrich Miescher Laboratory of the Max Planck Society, Tuebingen, Germany
| | - John R Weir
- Structural Biochemistry of Meiosis Group, Friedrich Miescher Laboratory of the Max Planck Society, Tuebingen, Germany.
| |
Collapse
|
39
|
Osia B, Twarowski J, Jackson T, Lobachev K, Liu L, Malkova A. Migrating bubble synthesis promotes mutagenesis through lesions in its template. Nucleic Acids Res 2022; 50:6870-6889. [PMID: 35748867 PMCID: PMC9262586 DOI: 10.1093/nar/gkac520] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 05/23/2022] [Accepted: 06/10/2022] [Indexed: 12/24/2022] Open
Abstract
Break-induced replication (BIR) proceeds via a migrating D-loop for hundreds of kilobases and is highly mutagenic. Previous studies identified long single-stranded (ss) nascent DNA that accumulates during leading strand synthesis to be a target for DNA damage and a primary source of BIR-induced mutagenesis. Here, we describe a new important source of mutagenic ssDNA formed during BIR: the ssDNA template for leading strand BIR synthesis formed during D-loop migration. Specifically, we demonstrate that this D-loop bottom template strand (D-BTS) is susceptible to APOBEC3A (A3A)-induced DNA lesions leading to mutations associated with BIR. Also, we demonstrate that BIR-associated ssDNA promotes an additional type of genetic instability: replication slippage between microhomologies stimulated by inverted DNA repeats. Based on our results we propose that these events are stimulated by both known sources of ssDNA formed during BIR, nascent DNA formed by leading strand synthesis, and the D-BTS that we describe here. Together we report a new source of mutagenesis during BIR that may also be shared by other homologous recombination pathways driven by D-loop repair synthesis.
Collapse
Affiliation(s)
| | | | - Tyler Jackson
- Department of Biology, University of Iowa, Iowa City, IA 52245, USA,Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Kirill Lobachev
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GE 30332, USA
| | - Liping Liu
- Department of Biology, University of Iowa, Iowa City, IA 52245, USA
| | - Anna Malkova
- To whom correspondence should be addressed. Tel: +1 319 384 1285;
| |
Collapse
|
40
|
Li J, Ma J, Kumar V, Fu H, Xu C, Wang S, Jia Q, Fan Q, Xi X, Li M, Liu H, Lu Y. Identification of flexible Pif1-DNA interactions and their impacts on enzymatic activities. Nucleic Acids Res 2022; 50:7002-7012. [PMID: 35748877 PMCID: PMC9262596 DOI: 10.1093/nar/gkac529] [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: 12/12/2021] [Revised: 05/31/2022] [Accepted: 06/07/2022] [Indexed: 12/24/2022] Open
Abstract
Flexible regions in biomolecular complexes, although crucial to understanding structure-function relationships, are often unclear in high-resolution crystal structures. In this study, we showed that single-molecule techniques, in combination with computational modeling, can characterize dynamic conformations not resolved by high-resolution structure determination methods. Taking two Pif1 helicases (ScPif1 and BsPif1) as model systems, we found that, besides a few tightly bound nucleotides, adjacent solvent-exposed nucleotides interact dynamically with the helicase surfaces. The whole nucleotide segment possessed curved conformations and covered the two RecA-like domains of the helicases, which are essential for the inch-worm mechanism. The synergetic approach reveals that the interactions between the exposed nucleotides and the helicases could be reduced by large stretching forces or electrostatically shielded with high-concentration salt, subsequently resulting in reduced translocation rates of the helicases. The dynamic interactions between the exposed nucleotides and the helicases underlay the force- and salt-dependences of their enzymatic activities. The present single-molecule based approach complements high-resolution structural methods in deciphering the molecular mechanisms of the helicases.
Collapse
Affiliation(s)
| | | | | | - Hang Fu
- Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou, Zhejiang 325011, China,School of Physics, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Chunhua Xu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Shuang Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Qi Jia
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China,Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - Qinkai Fan
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China,School of Physics, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xuguang Xi
- Laboratoire de Biologie et Pharmacologie Appliquée (LBPA), UMR8113 CNRS, ENS Paris-Saclay, Université Paris-Saclay, Gif-sur-Yvette F-91190, France
| | - Ming Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China,Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China,School of Physics, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Haiguang Liu
- Correspondence may also be addressed to Haiguang Liu. Tel: +86 10 56981816;
| | - Ying Lu
- To whom correspondence should be addressed. Tel: +86 10 82648122;
| |
Collapse
|
41
|
Uribe-Calvillo T, Maestroni L, Marsolier MC, Khadaroo B, Arbiol C, Schott J, Llorente B. Comprehensive analysis of cis- and trans-acting factors affecting ectopic Break-Induced Replication. PLoS Genet 2022; 18:e1010124. [PMID: 35727827 PMCID: PMC9249352 DOI: 10.1371/journal.pgen.1010124] [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: 03/01/2022] [Revised: 07/01/2022] [Accepted: 05/19/2022] [Indexed: 11/24/2022] Open
Abstract
Break-induced replication (BIR) is a highly mutagenic eukaryotic homologous DNA recombination pathway that repairs one-ended DNA double strand breaks such as broken DNA replication forks and eroded telomeres. While searching for cis-acting factors regulating ectopic BIR efficiency, we found that ectopic BIR efficiency is the highest close to chromosome ends. The variations of ectopic BIR efficiency as a function of the length of DNA to replicate can be described as a combination of two decreasing exponential functions, a property in line with repeated cycles of strand invasion, elongation and dissociation that characterize BIR. Interestingly, the apparent processivity of ectopic BIR depends on the length of DNA already synthesized. Ectopic BIR is more susceptible to disruption during the synthesis of the first ~35–40 kb of DNA than later, notably when the template chromatid is being transcribed or heterochromatic. Finally, we show that the Srs2 helicase promotes ectopic BIR from both telomere proximal and telomere distal regions in diploid cells but only from telomere proximal sites in haploid cells. Altogether, we bring new light on the factors impacting a last resort DNA repair pathway. DNA is a long molecule composed of two anti-parallel strands that can undergo breaks that need to be efficiently repaired to ensure genomic stability, hence preventing genetic diseases such as cancer. Homologous recombination is a major DNA repair pathway that copies DNA from intact homologous templates to seal DNA double strand breaks. Short DNA repair tracts are favored when homologous sequences for the two extremities of the broken molecule are present. However, when homologous sequences are present for only one extremity of the broken molecule, DNA repair synthesis can proceed up to the end of the chromosome, the telomere. This notably occurs at eroded telomeres when telomerase, the enzyme normally responsible for telomere elongation, is inactive, and at broken DNA replication intermediates. However, this Break-Induced Replication or BIR pathway is highly mutagenic. By initiating BIR at various distances from the telomere, we found that the length of DNA to synthesize significantly reduces BIR efficiency. Interestingly, our findings support two DNA synthesis phases, the first one being much less processive than the second one. Ultimately, this tends to restrain the use of this last resort DNA repair pathway to chromosome extremities notably when it takes place between non-allelic homologous sequences.
Collapse
Affiliation(s)
- Tannia Uribe-Calvillo
- Cancer Research Center of Marseille, CNRS UMR7258, Inserm U1068, Institut Paoli-Calmettes, Aix-Marseille Université UM105, Marseille, France
| | - Laetitia Maestroni
- Cancer Research Center of Marseille, CNRS UMR7258, Inserm U1068, Institut Paoli-Calmettes, Aix-Marseille Université UM105, Marseille, France
| | - Marie-Claude Marsolier
- Institute for Integrative Biology of the Cell (I2BC), Institut des sciences du vivant Frédéric Joliot, CNRS UMR 9198, CEA Saclay, Gif-sur-Yvette, France
- Eco-anthropologie (EA), Muséum national d’Histoire naturelle, CNRS, Université de Paris, Musée de l’Homme, Paris, France
| | - Basheer Khadaroo
- Cancer Research Center of Marseille, CNRS UMR7258, Inserm U1068, Institut Paoli-Calmettes, Aix-Marseille Université UM105, Marseille, France
| | - Christine Arbiol
- Cancer Research Center of Marseille, CNRS UMR7258, Inserm U1068, Institut Paoli-Calmettes, Aix-Marseille Université UM105, Marseille, France
| | - Jonathan Schott
- Cancer Research Center of Marseille, CNRS UMR7258, Inserm U1068, Institut Paoli-Calmettes, Aix-Marseille Université UM105, Marseille, France
| | - Bertrand Llorente
- Cancer Research Center of Marseille, CNRS UMR7258, Inserm U1068, Institut Paoli-Calmettes, Aix-Marseille Université UM105, Marseille, France
- * E-mail:
| |
Collapse
|
42
|
Nickens DG, Bochman ML. Genetic and biochemical interactions of yeast DNA helicases. Methods 2022; 204:234-240. [PMID: 35483549 DOI: 10.1016/j.ymeth.2022.04.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 04/19/2022] [Accepted: 04/22/2022] [Indexed: 12/13/2022] Open
Abstract
DNA helicases function in many types of nucleic acid transactions, and as such, they are vital for genome integrity. Although they are often considered individually, work from many groups demonstrates that these enzymes often genetically and biochemically interact in vivo. Here, we highlight methods to interrogate such interactions among the PIF1 (Pif1 and Rrm3) and RecQ (Hrq1 and Sgs1) family helicases in Saccharomyces cerevisiae. The interactions among these enzymes were investigated in vivo using deletion and inactivation alleles with a gross-chromosomal rearrangement (GCR) assay. Further, wild-type and inactive recombinant proteins were used to determine the effects of the helicases on telomerase activity in vitro. We found that synergistic increases in GCR rates often occur in double vs. single mutants, suggesting that the helicases function in distinct genome integrity pathways. Further, the recombinant helicases can function together in vitro to modulate telomerase activity. Overall, the data suggest that the interactions among the members of these DNA helicase families are multipartite and argue for a comprehensive systems biology approach to fully elucidate the physiological interplay between these enzymes.
Collapse
Affiliation(s)
- David G Nickens
- Molecular & Cellular Biochemistry Department, Indiana University, Bloomington, Indiana 47405 USA
| | - Matthew L Bochman
- Molecular & Cellular Biochemistry Department, Indiana University, Bloomington, Indiana 47405 USA.
| |
Collapse
|
43
|
Break-induced replication: unraveling each step. Trends Genet 2022; 38:752-765. [PMID: 35459559 DOI: 10.1016/j.tig.2022.03.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Revised: 03/11/2022] [Accepted: 03/14/2022] [Indexed: 10/18/2022]
Abstract
Break-induced replication (BIR) repairs one-ended double-strand DNA breaks through invasion into a homologous template followed by DNA synthesis. Different from S-phase replication, BIR copies the template DNA in a migrating displacement loop (D-loop) and results in conservative inheritance of newly synthesized DNA. This unusual mode of DNA synthesis makes BIR a source of various genetic instabilities like those associated with cancer in humans. This review focuses on recent progress in delineating the mechanism of Rad51-dependent BIR in budding yeast. In addition, we discuss new data that describe changes in BIR efficiency and fidelity on encountering replication obstacles as well as the implications of these findings for BIR-dependent processes such as telomere maintenance and the repair of collapsed replication forks.
Collapse
|
44
|
Malone EG, Thompson MD, Byrd AK. Role and Regulation of Pif1 Family Helicases at the Replication Fork. Int J Mol Sci 2022; 23:ijms23073736. [PMID: 35409096 PMCID: PMC8998199 DOI: 10.3390/ijms23073736] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 03/24/2022] [Accepted: 03/25/2022] [Indexed: 02/04/2023] Open
Abstract
Pif1 helicases are a multifunctional family of DNA helicases that are important for many aspects of genomic stability in the nucleus and mitochondria. Pif1 helicases are conserved from bacteria to humans. Pif1 helicases play multiple roles at the replication fork, including promoting replication through many barriers such as G-quadruplex DNA, the rDNA replication fork barrier, tRNA genes, and R-loops. Pif1 helicases also regulate telomerase and promote replication termination, Okazaki fragment maturation, and break-induced replication. This review highlights many of the roles and regulations of Pif1 at the replication fork that promote cellular health and viability.
Collapse
Affiliation(s)
- Emory G. Malone
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (E.G.M.); (M.D.T.)
| | - Matthew D. Thompson
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (E.G.M.); (M.D.T.)
| | - Alicia K. Byrd
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (E.G.M.); (M.D.T.)
- Winthrop P. Rockefeller Cancer Institute, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
- Correspondence: ; Tel.: +1-501-526-6488
| |
Collapse
|
45
|
Division of Labor by the HELQ, BLM, and FANCM Helicases during Homologous Recombination Repair in Drosophila melanogaster. Genes (Basel) 2022; 13:genes13030474. [PMID: 35328029 PMCID: PMC8951532 DOI: 10.3390/genes13030474] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 03/02/2022] [Accepted: 03/07/2022] [Indexed: 02/01/2023] Open
Abstract
Repair of DNA double-strand breaks by homologous recombination (HR) requires a carefully orchestrated sequence of events involving many proteins. One type of HR, synthesis-dependent strand annealing (SDSA), proceeds via the formation of a displacement loop (D-loop) when RAD51-coated single-stranded DNA invades a homologous template. The 3' end of the single-stranded DNA is extended by DNA synthesis. In SDSA, the D-loop is then disassembled prior to strand annealing. While many helicases can unwind D-loops in vitro, how their action is choreographed in vivo remains to be determined. To clarify the roles of various DNA helicases during SDSA, we used a double-strand gap repair assay to study the outcomes of homologous recombination repair in Drosophila melanogaster lacking the BLM, HELQ, and FANCM helicases. We found that the absence of any of these three helicases impairs gap repair. In addition, flies lacking both BLM and HELQ or HELQ and FANCM had more severe SDSA defects than the corresponding single mutants. In the absence of BLM, a large percentage of repair events were accompanied by flanking deletions. Strikingly, these deletions were mostly abolished in the blm helq and blm fancm double mutants. Our results suggest that the BLM, HELQ, and FANCM helicases play distinct roles during SDSA, with HELQ and FANCM acting early to promote the formation of recombination intermediates that are then processed by BLM to prevent repair by deletion-prone mechanisms.
Collapse
|
46
|
Whale AJ, King M, Hull RM, Krueger F, Houseley J. Stimulation of adaptive gene amplification by origin firing under replication fork constraint. Nucleic Acids Res 2022; 50:915-936. [PMID: 35018465 PMCID: PMC8789084 DOI: 10.1093/nar/gkab1257] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Revised: 11/26/2021] [Accepted: 12/06/2021] [Indexed: 02/06/2023] Open
Abstract
Adaptive mutations can cause drug resistance in cancers and pathogens, and increase the tolerance of agricultural pests and diseases to chemical treatment. When and how adaptive mutations form is often hard to discern, but we have shown that adaptive copy number amplification of the copper resistance gene CUP1 occurs in response to environmental copper due to CUP1 transcriptional activation. Here we dissect the mechanism by which CUP1 transcription in budding yeast stimulates copy number variation (CNV). We show that transcriptionally stimulated CNV requires TREX-2 and Mediator, such that cells lacking TREX-2 or Mediator respond normally to copper but cannot acquire increased resistance. Mediator and TREX-2 can cause replication stress by tethering transcribed loci to nuclear pores, a process known as gene gating, and transcription at the CUP1 locus causes a TREX-2-dependent accumulation of replication forks indicative of replication fork stalling. TREX-2-dependent CUP1 gene amplification occurs by a Rad52 and Rad51-mediated homologous recombination mechanism that is enhanced by histone H3K56 acetylation and repressed by Pol32 and Pif1. CUP1 amplification is also critically dependent on late-firing replication origins present in the CUP1 repeats, and mutations that remove or inactivate these origins strongly suppress the acquisition of copper resistance. We propose that replicative stress imposed by nuclear pore association causes replication bubbles from these origins to collapse soon after activation, leaving a tract of H3K56-acetylated chromatin that promotes secondary recombination events during elongation after replication fork re-start events. The capacity for inefficient replication origins to promote copy number variation renders certain genomic regions more fragile than others, and therefore more likely to undergo adaptive evolution through de novo gene amplification.
Collapse
Affiliation(s)
- Alex J Whale
- Epigenetics Programme, Babraham Institute, Cambridge, UK
| | - Michelle King
- Epigenetics Programme, Babraham Institute, Cambridge, UK
| | - Ryan M Hull
- Epigenetics Programme, Babraham Institute, Cambridge, UK
| | - Felix Krueger
- Babraham Bioinformatics, Babraham Institute, Cambridge, UK
| | | |
Collapse
|
47
|
Dutta A, Kwon Y, Sung P. Biochemical Analysis of RNA-DNA Hybrid and R-Loop Unwinding Via Motor Proteins. Methods Mol Biol 2022; 2528:305-316. [PMID: 35704200 DOI: 10.1007/978-1-0716-2477-7_20] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
R-loops, three-stranded RNA-DNA hybrids that arise mostly during transcription, could cause genomic instability via distinct routes. Detection of genomic RNA-DNA hybrids via immunofluorescence and RNA-DNA hybrid immunoprecipitation techniques have facilitated the discovery of many cellular factors that maintain R-loop homeostasis. One of multiple R-loop avoidance mechanisms is mediated by several nucleic acid motor proteins that utilize the energy from ATP hydrolysis to dissociate the R-loop structure. The biochemical activity of such motor proteins can be interrogated using synthetic R-loop substrates. Here, we describe methods to generate R-loop and RNA-DNA substrates for studying the activity of R-loop processing motor proteins such as human DHX9 and S. cerevisiae Pif1. Such studies provide valuable information regarding the directionality, nucleic acid strand preference, and processivity of these enzymes. Moreover, these substrates and companion biochemical assays provide the requisite tool for understanding the action of physiologically relevant regulators of these motor proteins.
Collapse
Affiliation(s)
- Arijit Dutta
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Youngho Kwon
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Patrick Sung
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
| |
Collapse
|
48
|
Yan Z, Liu L, Pham N, Thakre PK, Malkova A, Ira G. Measuring the contributions of helicases to break-induced replication. Methods Enzymol 2022; 672:339-368. [DOI: 10.1016/bs.mie.2022.02.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
|
49
|
Epum EA, Haber JE. DNA replication: the recombination connection. Trends Cell Biol 2022; 32:45-57. [PMID: 34384659 PMCID: PMC8688190 DOI: 10.1016/j.tcb.2021.07.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 07/18/2021] [Accepted: 07/20/2021] [Indexed: 01/03/2023]
Abstract
Failure to complete DNA replication is one of the major sources of genome instability leading to aneuploidy, chromosome breakage, and chromosome rearrangements that are associated with human cancer. One of the surprising revelations of the past decade is that the completion of replication at so-called common fragile sites (CFS) occurs very late in the cell cycle - at mitosis - through a process termed MiDAS (mitotic DNA synthesis). MiDAS is strongly related to another cancer-promoting phenomenon: the activation of alternative lengthening of telomeres (ALT). Our understanding of the mechanisms of ALT and MiDAS in mammalian cells has drawn heavily from recent advances in the study of break-induced replication (BIR), especially in budding yeast. We provide new insights into the BIR, MiDAS, and ALT pathways and their shared similarities.
Collapse
|
50
|
Abstract
The gene encoding the Pif1 helicase was first discovered in a Saccharomyces cerevisiae genetic screen as a mutant that reduces recombination between mitochondrial respiratory mutants and was subsequently rediscovered in a screen for genes affecting the telomere length in the nucleus. It is now known that Pif1 is involved in numerous aspects of DNA metabolism. All known functions of Pif1 rely on binding to DNA substrates followed by ATP hydrolysis, coupling the energy released to translocation along DNA to unwind duplex DNA or alternative DNA secondary structures. The interaction of Pif1 with higher-order DNA structures, like G-quadruplex DNA, as well as the length of single-stranded (ss)DNA necessary for Pif1 loading have been widely studied. Here, to test the effects of ssDNA length, sequence, and structure on Pif1's biochemical activities in vitro, we used a suite of oligonucleotide-based substrates to perform a basic characterization of Pif1 ssDNA binding, ATPase activity, and helicase activity. Using recombinant, untagged S. cerevisiae Pif1, we found that Pif1 preferentially binds to structured G-rich ssDNA, but the preferred binding substrates failed to maximally stimulate ATPase activity. In helicase assays, significant DNA unwinding activity was detected at Pif1 concentrations as low as 250 pM. Helicase assays also demonstrated that Pif1 most efficiently unwinds DNA fork substrates with unstructured ssDNA tails. As the chemical step size of Pif1 has been determined to be 1 ATP per translocation or unwinding event, this implies that the highly structured DNA inhibits conformational changes in Pif1 that couple ATP hydrolysis to DNA translocation and unwinding.
Collapse
Affiliation(s)
- David G Nickens
- Molecular & Cellular Biochemistry Department, Indiana University, Bloomington, Indiana 47405, United States
| | - Matthew L Bochman
- Molecular & Cellular Biochemistry Department, Indiana University, Bloomington, Indiana 47405, United States
| |
Collapse
|