1
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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.
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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
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2
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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.
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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;
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3
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Kockler ZW, Comeron JM, Malkova A. A unified alternative telomere-lengthening pathway in yeast survivor cells. Mol Cell 2021; 81:1816-1829.e5. [PMID: 33639094 DOI: 10.1016/j.molcel.2021.02.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 06/28/2020] [Accepted: 02/01/2021] [Indexed: 10/24/2022]
Abstract
Alternative lengthening of telomeres (ALT) is a recombination process that maintains telomeres in the absence of telomerase and helps cancer cells to survive. Yeast has been used as a robust model of ALT; however, the inability to determine the frequency and structure of ALT survivors hinders understanding of the ALT mechanism. Here, using population and molecular genetics approaches, we overcome these problems and demonstrate that contrary to the current view, both RAD51-dependent and RAD51-independent mechanisms are required for a unified ALT survivor pathway. This conclusion is based on the calculation of ALT frequencies, as well as on ultra-long sequencing of ALT products that revealed hybrid sequences containing features attributed to both recombination pathways. Sequencing of ALT intermediates demonstrates that recombination begins with Rad51-mediated strand invasion to form DNA substrates that are matured by a Rad51-independent ssDNA annealing pathway. A similar unified ALT pathway may operate in other organisms, including humans.
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Affiliation(s)
- Zachary W Kockler
- Department of Biology, University of Iowa, Iowa City, IA 52245, USA; Interdisciplinary Graduate Program in Genetics, University of Iowa, Iowa City, IA 52245, USA
| | - Josep M Comeron
- Department of Biology, University of Iowa, Iowa City, IA 52245, USA; Interdisciplinary Graduate Program in Genetics, University of Iowa, Iowa City, IA 52245, USA.
| | - Anna Malkova
- Department of Biology, University of Iowa, Iowa City, IA 52245, USA; Interdisciplinary Graduate Program in Genetics, University of Iowa, Iowa City, IA 52245, USA.
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4
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Liu L, Yan Z, Osia BA, Twarowski J, Sun L, Kramara J, Lee RS, Kumar S, Elango R, Li H, Dang W, Ira G, Malkova A. Tracking break-induced replication shows that it stalls at roadblocks. Nature 2021; 590:655-659. [PMID: 33473214 PMCID: PMC8219245 DOI: 10.1038/s41586-020-03172-w] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Accepted: 12/08/2020] [Indexed: 12/29/2022]
Abstract
Break-induced replication (BIR) repairs one-ended double strand breaks (DSBs) similar to those formed by replication collapse or telomere erosion, and it has been implicated in the initiation of genome instability in cancer and other human disease1,2. Previous studies have defined the enzymes required for BIR1–5; however, understanding of initial and extended BIR synthesis as well as how the migrating D-loop proceeds through known replication roadblocks has been precluded by technical limitations. Here, using a newly developed assay, we demonstrate that BIR synthesis initiates soon after strand invasion and proceeds slower than S-phase replication. Without primase, leading strand synthesis is initiated efficiently, but fails to proceed beyond 30 kb, suggesting that primase is needed for stabilization of the nascent leading strand. DNA synthesis can initiate in the absence of Pif1 or Pol32 but does not proceed efficiently. We demonstrate that interstitial telomeric DNA disrupts and terminates BIR progression. Also, BIR initiation is suppressed by transcription proportionally to the transcription level. Collisions between BIR and transcription lead to mutagenesis and chromosome rearrangements at levels that exceed instabilities induced by transcription during normal replication. Together, these results provide fundamental insights into the mechanism of BIR and on how BIR contributes to genome instability.
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Affiliation(s)
- Liping Liu
- Department of Biology, University of Iowa, Iowa City, IA, USA
| | - Zhenxin Yan
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Beth A Osia
- Department of Biology, University of Iowa, Iowa City, IA, USA
| | - Jerzy Twarowski
- Department of Biology, University of Iowa, Iowa City, IA, USA
| | - Luyang Sun
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.,Huffington Center on Aging, Baylor College of Medicine, Houston, TX, USA
| | - Juraj Kramara
- Department of Biology, University of Iowa, Iowa City, IA, USA
| | - Rosemary S Lee
- Department of Biology, University of Iowa, Iowa City, IA, USA
| | - Sandeep Kumar
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Rajula Elango
- Department of Biology, University of Iowa, Iowa City, IA, USA.,Department of Medicine, Division of Hematology-Oncology and Cancer Research Institute, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA
| | - Hanzeng Li
- Department of Internal Medicine, University of Iowa, Iowa City, IA, USA
| | - Weiwei Dang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.,Huffington Center on Aging, Baylor College of Medicine, Houston, TX, USA
| | - Grzegorz Ira
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.
| | - Anna Malkova
- Department of Biology, University of Iowa, Iowa City, IA, USA. .,Interdisciplinary Graduate Program in Genetics, University of Iowa, Iowa City, IA, USA.
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5
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Joseph SA, Taglialatela A, Leuzzi G, Huang JW, Cuella-Martin R, Ciccia A. Time for remodeling: SNF2-family DNA translocases in replication fork metabolism and human disease. DNA Repair (Amst) 2020; 95:102943. [PMID: 32971328 DOI: 10.1016/j.dnarep.2020.102943] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Revised: 07/24/2020] [Accepted: 07/26/2020] [Indexed: 02/07/2023]
Abstract
Over the course of DNA replication, DNA lesions, transcriptional intermediates and protein-DNA complexes can impair the progression of replication forks, thus resulting in replication stress. Failure to maintain replication fork integrity in response to replication stress leads to genomic instability and predisposes to the development of cancer and other genetic disorders. Multiple DNA damage and repair pathways have evolved to allow completion of DNA replication following replication stress, thus preserving genomic integrity. One of the processes commonly induced in response to replication stress is fork reversal, which consists in the remodeling of stalled replication forks into four-way DNA junctions. In normal conditions, fork reversal slows down replication fork progression to ensure accurate repair of DNA lesions and facilitates replication fork restart once the DNA lesions have been removed. However, in certain pathological situations, such as the deficiency of DNA repair factors that protect regressed forks from nuclease-mediated degradation, fork reversal can cause genomic instability. In this review, we describe the complex molecular mechanisms regulating fork reversal, with a focus on the role of the SNF2-family fork remodelers SMARCAL1, ZRANB3 and HLTF, and highlight the implications of fork reversal for tumorigenesis and cancer therapy.
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Affiliation(s)
- Sarah A Joseph
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Angelo Taglialatela
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Giuseppe Leuzzi
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Jen-Wei Huang
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Raquel Cuella-Martin
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Alberto Ciccia
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA.
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6
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Xing M, Zhang F, Liao H, Chen S, Che L, Wang X, Bao Z, Ji F, Chen G, Zhang H, Li W, Chen Z, Liu Y, Hickson ID, Shen H, Ying S. Replication Stress Induces ATR/CHK1-Dependent Nonrandom Segregation of Damaged Chromosomes. Mol Cell 2020; 78:714-724.e5. [PMID: 32353258 DOI: 10.1016/j.molcel.2020.04.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 02/22/2020] [Accepted: 04/06/2020] [Indexed: 12/15/2022]
Abstract
Nonrandom DNA segregation (NDS) is a mitotic event in which sister chromatids carrying the oldest DNA strands are inherited exclusively by one of the two daughter cells. Although this phenomenon has been observed across various organisms, the mechanism and physiological relevance of this event remain poorly defined. Here, we demonstrate that DNA replication stress can trigger NDS in human cells. This biased inheritance of old template DNA is associated with the asymmetric DNA damage response (DDR), which derives at least in part from telomeric DNA. Mechanistically, we reveal that the ATR/CHK1 signaling pathway plays an essential role in mediating NDS. We show that this biased segregation process leads to cell-cycle arrest and cell death in damaged daughter cells inheriting newly replicated DNA. These data therefore identify a key role for NDS in the maintenance of genomic integrity within cancer cell populations undergoing replication stress due to oncogene activation.
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Affiliation(s)
- Meichun Xing
- Department of Pharmacology and Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Zhejiang University School of Medicine, Key Laboratory of Respiratory Disease of Zhejiang Province, Hangzhou 310009, China
| | - Fengjiao Zhang
- Department of Pharmacology and Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Zhejiang University School of Medicine, Key Laboratory of Respiratory Disease of Zhejiang Province, Hangzhou 310009, China
| | - Hongwei Liao
- Department of Pharmacology and Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Zhejiang University School of Medicine, Key Laboratory of Respiratory Disease of Zhejiang Province, Hangzhou 310009, China
| | - Sisi Chen
- Department of Pharmacology and Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Zhejiang University School of Medicine, Key Laboratory of Respiratory Disease of Zhejiang Province, Hangzhou 310009, China
| | - Luanqing Che
- Key Laboratory of Respiratory Disease of Zhejiang Province, Department of Respiratory and Critical Care Medicine, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, China
| | - Xiaohui Wang
- Department of Pharmacology and Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Zhejiang University School of Medicine, Key Laboratory of Respiratory Disease of Zhejiang Province, Hangzhou 310009, China
| | - Zhengqiang Bao
- Department of Pharmacology and Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Zhejiang University School of Medicine, Key Laboratory of Respiratory Disease of Zhejiang Province, Hangzhou 310009, China
| | - Fang Ji
- Department of Pharmacology and Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Zhejiang University School of Medicine, Key Laboratory of Respiratory Disease of Zhejiang Province, Hangzhou 310009, China
| | - Gaoying Chen
- Department of Pharmacology and Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Zhejiang University School of Medicine, Key Laboratory of Respiratory Disease of Zhejiang Province, Hangzhou 310009, China
| | - Huihui Zhang
- Department of Pharmacology and Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Zhejiang University School of Medicine, Key Laboratory of Respiratory Disease of Zhejiang Province, Hangzhou 310009, China
| | - Wen Li
- Key Laboratory of Respiratory Disease of Zhejiang Province, Department of Respiratory and Critical Care Medicine, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, China
| | - Zhihua Chen
- Key Laboratory of Respiratory Disease of Zhejiang Province, Department of Respiratory and Critical Care Medicine, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, China
| | - Ying Liu
- Center for Chromosome Stability and Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark
| | - Ian D Hickson
- Center for Chromosome Stability and Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark.
| | - Huahao Shen
- Key Laboratory of Respiratory Disease of Zhejiang Province, Department of Respiratory and Critical Care Medicine, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, China; State Key Laboratory of Respiratory Diseases, Guangzhou, Guangdong 510120, China.
| | - Songmin Ying
- Department of Pharmacology and Department of Respiratory and Critical Care Medicine of the Second Affiliated Hospital, Zhejiang University School of Medicine, Key Laboratory of Respiratory Disease of Zhejiang Province, Hangzhou 310009, China.
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7
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Li J, Sun H, Huang Y, Wang Y, Liu Y, Chen X. Pathways and assays for DNA double-strand break repair by homologous recombination. Acta Biochim Biophys Sin (Shanghai) 2019; 51:879-889. [PMID: 31294447 DOI: 10.1093/abbs/gmz076] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Accepted: 06/17/2019] [Indexed: 12/11/2022] Open
Abstract
Double strand breaks (DSBs) are the most detrimental type of DNA damage that must be repaired to ensure genome integrity and cell survival. Unrepaired or improperly repaired DSBs can potentially cause tumorigenesis or cell death. DSBs are primarily repaired by non-homologous end joining or homologous recombination (HR). The HR pathway is initiated by processing of the 5'-end of DSBs to generate 3'-end single-strand DNA (ssDNA). Furthermore, the intermediate is channeled to one of the HR sub-pathways, including: (i) double Holliday junction (dHJ) pathway, (ii) synthesis-dependent strand annealing (SDSA), (iii) break-induced replication (BIR), and (iv) single-strand annealing (SSA). In the dHJ sub-pathway, the 3'-ssDNA coated with Rad51 recombinase performs homology search and strand invasion, forming a displacement loop (D-loop). Capture of the second end by the D-loop generates a dHJ intermediate that is subsequently dissolved by DNA helicase or resolved by nucleases, producing non-crossover or crossover products. In SDSA, the newly synthesized strand is displaced from the D-loop and anneals to the end on the other side of the DSBs, producing non-crossovers. In contrast, BIR repairs one-end DSBs by copying the sequence up to the end of the template chromosome, resulting in translocation or loss of heterozygosity. SSA takes place when resection reveals flanking homologous repeats that can anneal, leading to deletion of the intervening sequences. A variety of reporter assays have been developed to monitor distinct HR sub-pathways in both Saccharomyces cerevisiae and mammals. Here, we summarize the principles and representative assays for different HR sub-pathways with an emphasis on the studies in the budding yeast.
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Affiliation(s)
- Jinbao Li
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences and the Institute for Advanced Studies, Wuhan University, Wuhan, China
| | - Huize Sun
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences and the Institute for Advanced Studies, Wuhan University, Wuhan, China
| | - Yulin Huang
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences and the Institute for Advanced Studies, Wuhan University, Wuhan, China
| | - Yali Wang
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences and the Institute for Advanced Studies, Wuhan University, Wuhan, China
| | - Yuyan Liu
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences and the Institute for Advanced Studies, Wuhan University, Wuhan, China
| | - Xuefeng Chen
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences and the Institute for Advanced Studies, Wuhan University, Wuhan, China
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8
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Ramakrishnan S, Kockler Z, Evans R, Downing BD, Malkova A. Single-strand annealing between inverted DNA repeats: Pathway choice, participating proteins, and genome destabilizing consequences. PLoS Genet 2018; 14:e1007543. [PMID: 30091972 PMCID: PMC6103520 DOI: 10.1371/journal.pgen.1007543] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Revised: 08/21/2018] [Accepted: 07/06/2018] [Indexed: 11/19/2022] Open
Abstract
Double strand DNA breaks (DSBs) are dangerous events that can result from various causes including environmental assaults or the collapse of DNA replication. While the efficient and precise repair of DSBs is essential for cell survival, faulty repair can lead to genetic instability, making the choice of DSB repair an important step. Here we report that inverted DNA repeats (IRs) placed near a DSB can channel its repair from an accurate pathway that leads to gene conversion to instead a break-induced replication (BIR) pathway that leads to genetic instabilities. The effect of IRs is explained by their ability to form unusual DNA structures when present in ssDNA that is formed by DSB resection. We demonstrate that IRs can form two types of unusual DNA structures, and the choice between these structures depends on the length of the spacer separating IRs. In particular, IRs separated by a long (1-kb) spacer are predominantly involved in inter-molecular single-strand annealing (SSA) leading to the formation of inverted dimers; IRs separated by a short (12-bp) spacer participate in intra-molecular SSA, leading to the formation of fold-back (FB) structures. Both of these structures interfere with an accurate DSB repair by gene conversion and channel DSB repair into BIR, which promotes genomic destabilization. We also report that different protein complexes participate in the processing of FBs containing short (12-bp) versus long (1-kb) ssDNA loops. Specifically, FBs with short loops are processed by the MRX-Sae2 complex, whereas the Rad1-Rad10 complex is responsible for the processing of long loops. Overall, our studies uncover the mechanisms of genomic destabilization resulting from re-routing DSB repair into unusual pathways by IRs. Given the high abundance of IRs in the human genome, our findings may contribute to the understanding of IR-mediated genomic destabilization associated with human disease. Efficient and accurate repair of double-strand DNA breaks (DSBs), resulting from the exposure of cells to ionizing radiation or various chemicals, is crucial for cell survival. Conversely, faulty DSB repair can generate genomic instability that can lead to birth defects or cancer in humans. Here we demonstrate that inverted DNA repeats (IRs) placed in the vicinity of a DSB, interfere with the accurate repair of DSBs and promote genomic rearrangements and chromosome loss. This results from annealing between inverted repeats, located either in different DNA molecules or in the same molecule. In addition, we describe a new role for the Rad1-Rad10 protein complex in processing fold-back (FB) structures formed by intra-molecular annealing involving IRs separated by long spacers. In contrast, FBs with short spacers are processed by the Mre11-Rad50-Xrs2/-Sae2 complex. Overall, we describe several pathways of DSB promoted interaction between IRs that can lead to genomic instability. Given the large number of IRs in the human genome, our findings are relevant to the mechanisms driving genomic destabilization in humans contributing to the development of cancer and other diseases.
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Affiliation(s)
- Sreejith Ramakrishnan
- Department of Biology, University of Iowa, Iowa City, IA, United States of America
- Indiana University Purdue University Indianapolis, Indianapolis, IN, United States of America
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, CA, United States of America
| | - Zachary Kockler
- Department of Biology, University of Iowa, Iowa City, IA, United States of America
| | - Robert Evans
- Indiana University Purdue University Indianapolis, Indianapolis, IN, United States of America
| | - Brandon D. Downing
- Indiana University Purdue University Indianapolis, Indianapolis, IN, United States of America
| | - Anna Malkova
- Department of Biology, University of Iowa, Iowa City, IA, United States of America
- Indiana University Purdue University Indianapolis, Indianapolis, IN, United States of America
- * E-mail:
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