scholarly journals Effects of Mutations in DNA Repair Genes on Formation of Ribosomal DNA Circles and Life Span inSaccharomyces cerevisiae

1999 ◽  
Vol 19 (5) ◽  
pp. 3848-3856 ◽  
Author(s):  
Peter U. Park ◽  
Pierre-Antoine Defossez ◽  
Leonard Guarente
Keyword(s):  
Dna Repair ◽  
Homologous Recombination ◽  
Life Span ◽  
Ribosomal Dna ◽  
Initial Step ◽  
Double Strand Breaks ◽  
Strand Breaks ◽  
Mother Cells ◽  
Mutant Cells ◽  
Repair Genes

ABSTRACT A cause of aging in Saccharomyces cerevisiae is the accumulation of extrachromosomal ribosomal DNA circles (ERCs). Introduction of an ERC into young mother cells shortens life span and accelerates the onset of age-associated sterility. It is important to understand the process by which ERCs are generated. Here, we demonstrate that homologous recombination is necessary for ERC formation. rad52 mutant cells, defective in DNA repair through homologous recombination, do not accumulate ERCs with age, and mutations in other genes of the RAD52 class have varying effects on ERC formation. rad52 mutation leads to a progressive delocalization of Sir3p from telomeres to other nuclear sites with age and, surprisingly, shortens life span. We speculate that spontaneous DNA damage, perhaps double-strand breaks, causes lethality in mutants of the RAD52 class and may be an initial step of aging in wild-type cells.

scholarly journals End-resection at DNA double-strand breaks in the three domains of life

2013 ◽  
Vol 41 (1) ◽  
pp. 314-320 ◽  
Author(s):  
John K. Blackwood ◽  
Neil J. Rzechorzek ◽  
Sian M. Bray ◽  
Joseph D. Maman ◽  
Luca Pellegrini ◽  
...  
Keyword(s):  
Dna Repair ◽  
Homologous Recombination ◽  
Strand Break ◽  
Double Strand Breaks ◽  
Dna Double Strand Breaks ◽  
Strand Breaks ◽  
Homologous Chromosomes ◽  
Domains Of Life ◽  
Strand Invasion ◽  
End Resection

During DNA repair by HR (homologous recombination), the ends of a DNA DSB (double-strand break) must be resected to generate single-stranded tails, which are required for strand invasion and exchange with homologous chromosomes. This 5′–3′ end-resection of the DNA duplex is an essential process, conserved across all three domains of life: the bacteria, eukaryota and archaea. In the present review, we examine the numerous and redundant helicase and nuclease systems that function as the enzymatic analogues for this crucial process in the three major phylogenetic divisions.

scholarly journals Recent advances in the nucleolar responses to DNA double-strand breaks

2020 ◽  
Vol 48 (17) ◽  
pp. 9449-9461
Author(s):  
Lea Milling Korsholm ◽  
Zita Gál ◽  
Blanca Nieto ◽  
Oliver Quevedo ◽  
Stavroula Boukoura ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Dna Damage Response ◽  
Ribosomal Dna ◽  
Repetitive Sequences ◽  
Dna Lesions ◽  
Double Strand Breaks ◽  
Dna Double Strand Breaks ◽  
Strand Breaks ◽  
Damage Response

Abstract DNA damage poses a serious threat to human health and cells therefore continuously monitor and repair DNA lesions across the genome. Ribosomal DNA is a genomic domain that represents a particular challenge due to repetitive sequences, high transcriptional activity and its localization in the nucleolus, where the accessibility of DNA repair factors is limited. Recent discoveries have significantly extended our understanding of how cells respond to DNA double-strand breaks (DSBs) in the nucleolus, and new kinases and multiple down-stream targets have been identified. Restructuring of the nucleolus can occur as a consequence of DSBs and new data point to an active regulation of this process, challenging previous views. Furthermore, new insights into coordination of cell cycle phases and ribosomal DNA repair argue against existing concepts. In addition, the importance of nucleolar-DNA damage response (n-DDR) mechanisms for maintenance of genome stability and the potential of such factors as anti-cancer targets is becoming apparent. This review will provide a detailed discussion of recent findings and their implications for our understanding of the n-DDR. The n-DDR shares features with the DNA damage response (DDR) elsewhere in the genome but is also emerging as an independent response unique to ribosomal DNA and the nucleolus.

scholarly journals Super-resolution mapping of cellular double-strand break resection complexes during homologous recombination

2021 ◽  
Vol 118 (11) ◽  
pp. e2021963118
Author(s):  
Donna R. Whelan ◽  
Eli Rothenberg
Keyword(s):  
Homologous Recombination ◽  
Single Molecule ◽  
Protein A ◽  
Super Resolution ◽  
Initial Step ◽  
Double Strand Breaks ◽  
Homology Search ◽  
Major Pathway ◽  
Strand Breaks

Homologous recombination (HR) is a major pathway for repair of DNA double-strand breaks (DSBs). The initial step that drives the HR process is resection of DNA at the DSB, during which a multitude of nucleases, mediators, and signaling proteins accumulates at the damage foci in a manner that remains elusive. Using single-molecule localization super-resolution (SR) imaging assays, we specifically visualize the spatiotemporal behavior of key mediator and nuclease proteins as they resect DNA at single-ended double-strand breaks (seDSBs) formed at collapsed replication forks. By characterizing these associations, we reveal the in vivo dynamics of resection complexes involved in generating the long single-stranded DNA (ssDNA) overhang prior to homology search. We show that 53BP1, a protein known to antagonize HR, is recruited to seDSB foci during early resection but is spatially separated from repair activities. Contemporaneously, CtBP-interacting protein (CtIP) and MRN (MRE11-RAD51-NBS1) associate with seDSBs, interacting with each other and BRCA1. The HR nucleases EXO1 and DNA2 are also recruited and colocalize with each other and with the repair helicase Bloom syndrome protein (BLM), demonstrating multiple simultaneous resection events. Quantification of replication protein A (RPA) accumulation and ssDNA generation shows that resection is completed 2 to 4 h after break induction. However, both BRCA1 and BLM persist later into HR, demonstrating potential roles in homology search and repair resolution. Furthermore, we show that initial recruitment of BRCA1 and removal of Ku are largely independent of MRE11 exonuclease activity but dependent on MRE11 endonuclease activity. Combined, our observations provide a detailed description of resection during HR repair.

scholarly journals Bacterial DNA repair genes and their eukaryotic homologues: 5. The role of recombination in DNA repair and genome stability.

2007 ◽  
Vol 54 (3) ◽  
pp. 483-494 ◽  
Author(s):  
Anetta Nowosielska
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Dna Replication ◽  
Homologous Recombination ◽  
Genetic Material ◽  
Double Strand Breaks ◽  
Single Strand ◽  
Biological Processes ◽  
Strand Breaks ◽  
Immune System Development

Recombinational repair is a well conserved DNA repair mechanism present in all living organisms. Repair by homologous recombination is generally accurate as it uses undamaged homologous DNA molecule as a repair template. In Escherichia coli homologous recombination repairs both the double-strand breaks and single-strand gaps in DNA. DNA double-strand breaks (DSB) can be induced upon exposure to exogenous sources such as ionizing radiation or endogenous DNA-damaging agents including reactive oxygen species (ROS) as well as during natural biological processes like conjugation. However, the bulk of double strand breaks are formed during replication fork collapse encountering an unrepaired single strand gap in DNA. Under such circumstances DNA replication on the damaged template can be resumed only if supported by homologous recombination. This functional cooperation of homologous recombination with replication machinery enables successful completion of genome duplication and faithful transmission of genetic material to a daughter cell. In eukaryotes, homologous recombination is also involved in essential biological processes such as preservation of genome integrity, DNA damage checkpoint activation, DNA damage repair, DNA replication, mating type switching, transposition, immune system development and meiosis. When unregulated, recombination can lead to genome instability and carcinogenesis.

scholarly journals RNF19A-mediated ubiquitination of BARD1 prevents BRCA1/BARD1-dependent homologous recombination

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Qian Zhu ◽  
Jinzhou Huang ◽  
Hongyang Huang ◽  
Huan Li ◽  
Peiqiang Yi ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Dna Repair ◽  
Homologous Recombination ◽  
Cancer Cell ◽  
Nuclear Export ◽  
Molecular Mechanisms ◽  
Double Strand Breaks ◽  
Dna Double Strand Breaks ◽  
Strand Breaks ◽  
Polymerase Inhibitors

AbstractBRCA1-BARD1 heterodimers act in multiple steps during homologous recombination (HR) to ensure the prompt repair of DNA double strand breaks. Dysfunction of the BRCA1 pathway enhances the therapeutic efficiency of poly-(ADP-ribose) polymerase inhibitors (PARPi) in cancers, but the molecular mechanisms underlying this sensitization to PARPi are not fully understood. Here, we show that cancer cell sensitivity to PARPi is promoted by the ring between ring fingers (RBR) protein RNF19A. We demonstrate that RNF19A suppresses HR by ubiquitinating BARD1, which leads to dissociation of BRCA1-BARD1 complex and exposure of a nuclear export sequence in BARD1 that is otherwise masked by BRCA1, resulting in the export of BARD1 to the cytoplasm. We provide evidence that high RNF19A expression in breast cancer compromises HR and increases sensitivity to PARPi. We propose that RNF19A modulates the cancer cell response to PARPi by negatively regulating the BRCA1-BARD1 complex and inhibiting HR-mediated DNA repair.

scholarly journals TOPBP1 takes RADical command in recombinational DNA repair

2016 ◽  
Vol 212 (3) ◽  
pp. 263-266 ◽  
Author(s):  
Yi Liu ◽  
Marcus B. Smolka
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Dna Replication ◽  
Homologous Recombination ◽  
Crucial Role ◽  
Double Strand Breaks ◽  
Strand Breaks ◽  
Dna Damage Signaling ◽  
Cell Biol ◽  
Recombinational Dna Repair

TOPBP1 is a key player in DNA replication and DNA damage signaling. In this issue, Moudry et al. (2016. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201507042) uncover a crucial role for TOPBP1 in DNA repair by revealing its requirement for RAD51 loading during repair of double strand breaks by homologous recombination.

scholarly journals Homologous Recombination Repair Factors Rad51 and BRCA1 Are Necessary for Productive Replication of Human Papillomavirus 31

2015 ◽  
Vol 90 (5) ◽  
pp. 2639-2652 ◽  
Author(s):  
William H. Chappell ◽  
Dipendra Gautam ◽  
Suzan T. Ok ◽  
Bryan A. Johnson ◽  
Daniel C. Anacker ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Human Papillomavirus ◽  
Homologous Recombination ◽  
Viral Replication ◽  
Dna Damage Response ◽  
Double Strand Breaks ◽  
Strand Breaks ◽  
Damage Response ◽  
Productive Replication

ABSTRACTHigh-risk human papillomavirus 31 (HPV31)-positive cells exhibit constitutive activation of the ATM-dependent DNA damage response (DDR), which is necessary for productive viral replication. In response to DNA double-strand breaks (DSBs), ATM activation leads to DNA repair through homologous recombination (HR), which requires the principal recombinase protein Rad51, as well as BRCA1. Previous studies from our lab demonstrated that Rad51 and BRCA1 are expressed at high levels in HPV31-positive cells and localize to sites of viral replication. These results suggest that HPV may utilize ATM activity to increase HR activity as a means to facilitate viral replication. In this study, we demonstrate that high-risk HPV E7 expression alone is sufficient for the increase in Rad51 and BRCA1 protein levels. We have found that this increase occurs, at least in part, at the level of transcription. Studies analyzing protein stability indicate that HPV may also protect Rad51 and BRCA1 from turnover, contributing to the overall increase in cellular levels. We also demonstrate that Rad51 is bound to HPV31 genomes, with binding increasing per viral genome upon productive replication. We have found that depletion of Rad51 and BRCA1, as well as inhibition of Rad51's recombinase activity, abrogates productive viral replication upon differentiation. Overall, these results indicate that Rad51 and BRCA1 are required for the process of HPV31 genome amplification and suggest that productive replication occurs in a manner dependent upon recombination.IMPORTANCEProductive replication of HPV31 requires activation of an ATM-dependent DNA damage response, though how ATM activity contributes to replication is unclear. Rad51 and BRCA1 play essential roles in repair of double-strand breaks, as well as the restart of stalled replication forks through homologous recombination (HR). Given that ATM activity is required to initiate HR repair, coupled with the requirement of Rad51 and BRCA1 for productive viral replication, our findings suggest that HPV may utilize ATM activity to ensure localization of recombination factors to productively replicating viral genomes. The finding that E7 increases the levels of Rad51 and BRCA1 suggests that E7 contributes to productive replication by providing DNA repair factors required for viral DNA synthesis. Our studies not only imply a role for recombination in the regulation of productive HPV replication but provide further insight into how HPV manipulates the DDR to facilitate the productive phase of the viral life cycle.

Molecular genetic analysis of the polymorphism of repair genes of double-strand breaks DNA strand breaks and repair «inconsistencies» DNA in workers of hazardous industries

2019 ◽  
Vol 1 (7) ◽  
pp. 395-399
Author(s):  
Тatyana A. Andrushchenko ◽  
Sergey V. Goncharov ◽  
Viktor Е. Dosenko ◽  
Konstantin E. Ischeikin
Keyword(s):  
Dna Repair ◽  
Respiratory System ◽  
Molecular Genetic ◽  
Molecular Genetic Analysis ◽  
Double Strand Breaks ◽  
Dna Repair Genes ◽  
Dna Breaks ◽  
Strand Breaks ◽  
Increased Risk ◽  
Repair Genes

Introduction. Presents results of a study of polymorphisms of repair genes of double-strand breaks DNA breaks: XRCC7 (rs7003908), ATM (rs664677), repair «inconsistencies» DNA MLH1 (rs1799977) in miners and workers of asbestos factories professionally due to broncho-pulmonary pathology. T e aim of the study was to research the frequency distribution of genotypes of DNA repair genes: XRCC7 (rs7003908), ATM (rs664677) and MLH1 (rs1799977) in workers of harmful and dangerous industries to identify markers of increased risk of bronchopulmonary pathology. Materials and methods. In 90 people with bronchopulmonary pathology and 124 respondents who worked in the same working conditions but had no history of diseases of the respiratory system, polymerase chain reaction in real time studied the polymorphism of DNA repair genes: XRCC7 (rs7003908), ATM (rs664677) and MLH1 (rs1799977). Results. It was found that the genotypes ATM×T/T and MLH1×A/G are associated with the risk of bronchopulmonary pathology. Genotypes that contribute to resistance to the development of respiratory system pathology were also established: ATM×A/A, ATM× A/T and MLH1×A/A. Conclusion. Genotypes associated with the risk of bronchopulmonary pathology were established: ATM×T/T (р≤0.01, χ2=6.61; OR=2.48; 95%CI: 1.16–5.31) and MLH1×A/G (p≤0.002, χ2=9.00; OR=2.32; 95%CI: 1.29–4.21). Also determined the genotypes that contribute to resistance to the development of diseases of the respiratory system: ATM×a/A (OR=0,83; 95%CI: 0,45–1,54), ATM×A/T (OR=0,67; 95% CI: 0,38–1,21) and MLH1× a/A (р≤0,003, χ2=8,73; OR=0,43; 95% CI: 0,24–0,79).

scholarly journals PHF2 regulates homology-directed DNA repair by controlling the resection of DNA double strand breaks

2020 ◽  
Vol 48 (9) ◽  
pp. 4915-4927 ◽  
Author(s):  
Ignacio Alonso-de Vega ◽  
Maria Cristina Paz-Cabrera ◽  
Magdalena B Rother ◽  
Wouter W Wiegant ◽  
Cintia Checa-Rodríguez ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Homologous Recombination ◽  
Strand Break ◽  
Double Strand Break ◽  
Double Strand Breaks ◽  
Double Strand Break Repair ◽  
Focus Formation ◽  
Strand Breaks ◽  
Break Repair

Abstract Post-translational histone modifications and chromatin remodelling play a critical role controlling the integrity of the genome. Here, we identify histone lysine demethylase PHF2 as a novel regulator of the DNA damage response by regulating DNA damage-induced focus formation of 53BP1 and BRCA1, critical factors in the pathway choice for DNA double strand break repair. PHF2 knockdown leads to impaired BRCA1 focus formation and delays the resolution of 53BP1 foci. Moreover, irradiation-induced RPA phosphorylation and focus formation, as well as localization of CtIP, required for DNA end resection, to sites of DNA lesions are affected by depletion of PHF2. These results are indicative of a defective resection of double strand breaks and thereby an impaired homologous recombination upon PHF2 depletion. In accordance with these data, Rad51 focus formation and homology-directed double strand break repair is inhibited in cells depleted for PHF2. Importantly, we demonstrate that PHF2 knockdown decreases CtIP and BRCA1 protein and mRNA levels, an effect that is dependent on the demethylase activity of PHF2. Furthermore, PHF2-depleted cells display genome instability and are mildly sensitive to the inhibition of PARP. Together these results demonstrate that PHF2 promotes DNA repair by homologous recombination by controlling CtIP-dependent resection of double strand breaks.

RPA phosphorylation facilitates RAD52 dependent homologous recombination in BRCA-deficient cells

2021 ◽  
Author(s):  
Alison C. Carley ◽  
Manisha Jalan ◽  
Shyamal Subramanyam ◽  
Rohini Roy ◽  
Gloria E.O. Borgstahl ◽  
...  
Keyword(s):  
Homologous Recombination ◽  
Mammalian Cells ◽  
Protein A ◽  
Double Strand Breaks ◽  
Strand Exchange ◽  
Dna Duplexes ◽  
Dna Double Strand Breaks ◽  
Strand Breaks ◽  
Synthetically Lethal ◽  
Mutant Cells

Loss of RAD52 is synthetically lethal in BRCA-deficient cells, owing to its role in backup homologous recombination (HR) repair of DNA double-strand breaks (DSBs). In HR in mammalian cells, DSBs are processed to single-stranded DNA (ssDNA) overhangs, which are then bound by Replication Protein A(RPA). RPA is exchanged for RAD51 by mediator proteins: in mammals BRCA2 is the primary mediator, however, RAD52 provides an alternative mediator pathway in BRCA-deficient cells. RAD51 stimulates strand exchange between homologous DNA duplexes, a critical step in HR. RPA phosphorylation and de-phosphorylation are important for HR, but its effect on RAD52 mediator function is unknown. Here, we show that RPA phosphorylation is required for RAD52 to salvage HR in BRCA-deficient cells. Using BRCA2-depleted human cells, in which the only available mediator pathway is RAD52-dependent, the expression of phosphorylation-deficient RPA mutant reduced HR. Furthermore, RPA-phospho-mutant cells showed reduced association of RAD52 with RAD51. Interestingly, there was no effect of RPA phosphorylation on RAD52 recruitment to repair foci. Finally, we show that RPA phosphorylation does not affect RAD52-dependent ssDNA annealing. Thus, although RAD52 can be recruited independently of RPA’s phosphorylation status, RPA phosphorylation is required for RAD52’s association with RAD51, and its subsequent promotion of RAD52-mediated HR.

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