Involvement of DNA polymerase μ in the repair of a specific subset of DNA double-strand breaks in mammalian cells

In mammalian cells, the repair of DNA double-strand breaks (DSBs) occurs by both homologous and non-homologous mechanisms. Indirect evidence, including that from gene targeting and random integration experiments, had suggested that non-homologous mechanisms were significantly more frequent than homologous ones. However, more recent experiments indicate that homologous recombination is also a prominent DSB repair pathway. These experiments show that mammalian cells use homologous sequences located at multiple positions throughout the genome to repair a DSB. However, template preference appears to be biased, with the sister chromatid being preferred by 2–3 orders of magnitude over a homologous or heterologous chromosome. The outcome of homologous recombination in mammalian cells is predominantly gene conversion that is not associated with crossing-over. The preference for the sister chromatid and the bias against crossing-over seen in mitotic mammalian cells may have developed in order to reduce the potential for genome alterations that could occur when other homologous repair templates are utilized. In attempts to understand further the mechanism of homologous recombination, the proteins that promote this process are beginning to be identified. To date, four mammalian proteins have been demonstrated conclusively to be involved in DSB repair by homologous recombination: Rad54, XRCC2, XRCC3 and BRCAI. This paper summarizes results from a number of recent studies.

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Simultaneous determination of DNA double strand breaks and DNA fragment size in cultured mammalian cells exposed to hydrogen peroxide/histidine or etoposide with CHEF electrophoresis

Carcinogenesis ◽

10.1093/carcin/16.4.703 ◽

1995 ◽

Vol 16 (4) ◽

pp. 703-706 ◽

Cited By ~ 17

Author(s):

Piero Sestili ◽

Flaminio Cattabeni ◽

Orazio Cantoni

Keyword(s):

Hydrogen Peroxide ◽

Simultaneous Determination ◽

Mammalian Cells ◽

Fragment Size ◽

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

Strand Breaks ◽

Dna Fragment

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Homologous recombination preferentially repairs heat-induced DNA double-strand breaks in mammalian cells

International Journal of Hyperthermia ◽

10.1080/02656736.2016.1252989 ◽

2016 ◽

Vol 33 (3) ◽

pp. 336-342 ◽

Cited By ~ 6

Author(s):

Akihisa Takahashi ◽

Eiichiro Mori ◽

Yosuke Nakagawa ◽

Atsuhisa Kajihara ◽

Tadaaki Kirita ◽

...

Keyword(s):

Homologous Recombination ◽

Mammalian Cells ◽

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

Strand Breaks

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DNA polymerases δ and λ cooperate in repairing double-strand breaks by microhomology-mediated end-joining in Saccharomyces cerevisiae

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1507833112 ◽

2015 ◽

Vol 112 (50) ◽

pp. E6907-E6916 ◽

Cited By ~ 16

Author(s):

Damon Meyer ◽

Becky Xu Hua Fu ◽

Wolf-Dietrich Heyer

Keyword(s):

Saccharomyces Cerevisiae ◽

Dna Polymerase ◽

Genome Stability ◽

Double Strand Breaks ◽

Dna Polymerase Delta ◽

Dna Double Strand Breaks ◽

End Joining ◽

Strand Breaks ◽

Repair Efficiency ◽

Repair Pathways

Maintenance of genome stability is carried out by a suite of DNA repair pathways that ensure the repair of damaged DNA and faithful replication of the genome. Of particular importance are the repair pathways, which respond to DNA double-strand breaks (DSBs), and how the efficiency of repair is influenced by sequence homology. In this study, we developed a genetic assay in diploid Saccharomyces cerevisiae cells to analyze DSBs requiring microhomologies for repair, known as microhomology-mediated end-joining (MMEJ). MMEJ repair efficiency increased concomitant with microhomology length and decreased upon introduction of mismatches. The central proteins in homologous recombination (HR), Rad52 and Rad51, suppressed MMEJ in this system, suggesting a competition between HR and MMEJ for the repair of a DSB. Importantly, we found that DNA polymerase delta (Pol δ) is critical for MMEJ, independent of microhomology length and base-pairing continuity. MMEJ recombinants showed evidence that Pol δ proofreading function is active during MMEJ-mediated DSB repair. Furthermore, mutations in Pol δ and DNA polymerase 4 (Pol λ), the DNA polymerase previously implicated in MMEJ, cause a synergistic decrease in MMEJ repair. Pol λ showed faster kinetics associating with MMEJ substrates following DSB induction than Pol δ. The association of Pol δ depended on RAD1, which encodes the flap endonuclease needed to cleave MMEJ intermediates before DNA synthesis. Moreover, Pol δ recruitment was diminished in cells lacking Pol λ. These data suggest cooperative involvement of both polymerases in MMEJ.

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Detecting, signalling and repairing DNA double-strand breaks

Biochemical Society Transactions ◽

10.1042/bst0290655 ◽

2001 ◽

Vol 29 (6) ◽

pp. 655-661 ◽

Cited By ~ 70

Author(s):

S. P. Jackson

Keyword(s):

Mammalian Cells ◽

Molecular Mechanisms ◽

Double Strand Breaks ◽

Model Organisms ◽

Dna Double Strand Breaks ◽

Dsb Repair ◽

Site Specific ◽

Strand Breaks ◽

Dna Dsbs ◽

Recombination Processes

DNA double-strand breaks (DSBs) can be generated by a variety of genotoxic agents, including ionizing radiation and radiomimetic chemicals. They can also occur when DNA replication complexes encounter other forms of DNA damage, and are produced as intermediates during certain site-specific recombination processes. It is crucial that cells recognize DSBs and bring about their efficient repair, because a single unrepaired cellular DSB can induce cell death, and defective DSB repair can lead to mutations or the loss of significant segments of chromosomal material. Eukaryotic cells have evolved a variety of systems to detect DNA DSBs, repair them, and signal their presence to the transcription, cell cycle and apoptotic machineries. In this review, I describe how work on mammalian cells and also on model organisms such as yeasts has revelaed that such systems are highly conserved throughout evolution, and has provided insights into the molecular mechanisms by which DNA DSBs are recognized, signalled and repaired. I also explain how defects in the proteins that function in these pathways are associated with a variety of human pathological states.

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