Mre11 complex links sister chromatids to promote repair of a collapsed replication fork.
basic_science · Level V
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- Record sourced from PubMed, PMID 30104346.
- Also identified by DOI 10.1073/pnas.1808189115 and PMC identifier 6126713.
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Abstract
Collapsed replication forks, which are a major source of DNA double-strand breaks (DSBs), are repaired by sister chromatid recombination (SCR). The Mre11-Rad50-Nbs1 (MRN) protein complex, assisted by CtIP/Sae2/Ctp1, initiates SCR by nucleolytically resecting the single-ended DSB (seDSB) at the collapsed fork. The molecular architecture of the MRN intercomplex, in which zinc hooks at the apices of long Rad50 coiled-coils connect two Mre11<sub>2</sub>-Rad50<sub>2</sub> complexes, suggests that MRN also structurally assists SCR. Here, Rad50 ChIP assays in <i>Schizosaccharomyces pombe</i> show that MRN sequentially localizes with the seDSB and sister chromatid at a collapsed replication fork. Ctp1, which has multivalent DNA-binding and DNA-bridging activities, has the same DNA interaction pattern. Provision of an intrachromosomal repair template alleviates the nonnucleolytic requirement for MRN to repair the broken fork. Mutations of zinc-coordinating cysteines in the Rad50 hook severely impair SCR. These data suggest that the MRN complex facilitates SCR by linking the seDSB and sister chromatid.
Medical subject headings
- Chromatids
- Chromosomes, Fungal
- DNA Repair
- DNA, Fungal
- Exodeoxyribonucleases
- Multiprotein Complexes
- Schizosaccharomyces
- Schizosaccharomyces pombe Proteins