Mre11 complex links sister chromatids to promote repair of a collapsed replication fork

Min Zhu, Hongchang Zhao, Oliver Limbo, and Paul Russell
PNAS August 28, 2018 115 (35) 8793-8798; published ahead of print August 13, 2018 https://doi.org/10.1073/pnas.1808189115

  1. Edited by Richard D. Kolodner, Ludwig Institute for Cancer Research, La Jolla, CA, and approved July 12, 2018 (received for review May 15, 2018)

This article requires a subscription to view the full text. If you have a subscription you may use the login form below to view the article. Access to this article can also be purchased.

Significance

When replication forks collapse at single-strand DNA breaks, the resulting single-ended DNA double-strand breaks (seDSBs) are repaired by sister chromatid recombination (SCR). The Mre11–Rad50–Nbs1 (MRN) protein complex and CtIP/Ctp1 nucleolytically resect the seDSB to initiate SCR, but MRN was also proposed to promote SCR by tethering the seDSB to the unbroken sister chromatid. Here, we show that MRN sequentially localizes with the seDSB and sister chromatid during SCR. Provision of an intrachromosomal repair template alleviates the requirement for the nonnucleolytic function of MRN in repair of a collapsed replication fork. Zinc-coordinating “hooks” in Rad50 that are linchpins for MRN intercomplexes are essential for SCR. These studies support the MRN tethering hypothesis.

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 Mre112–Rad502 complexes, suggests that MRN also structurally assists SCR. Here, Rad50 ChIP assays in Schizosaccharomyces pombe 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.

Footnotes

  • ↵1M.Z. and H.Z. contributed equally to this work.

  • ↵2To whom correspondence should be addressed. Email: prussell{at}scripps.edu.

  • Author contributions: M.Z., H.Z., and P.R. designed research; M.Z., H.Z., and O.L. performed research; M.Z. and H.Z. contributed new reagents/analytic tools; M.Z., H.Z., O.L., and P.R. analyzed data; and M.Z., H.Z., and P.R. wrote the paper.

  • The authors declare no conflict of interest.

  • This article is a PNAS Direct Submission.

  • This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1808189115/-/DCSupplemental.

Published under the PNAS license.

View Full Text

Purchase access

You may purchase access to this article. This will require you to create an account if you don't already have one.
Back to top
Article Alerts
Email Article
Citation Tools
Request Permissions
Mre11 complex links sister chromatids to promote repair of a collapsed replication fork
Min Zhu, Hongchang Zhao, Oliver Limbo, Paul Russell
Proceedings of the National Academy of Sciences Aug 2018, 115 (35) 8793-8798; DOI: 10.1073/pnas.1808189115
del.icio.us logo Digg logo Reddit logo Twitter logo CiteULike logo Facebook logo Google logo Mendeley logo
Proceedings of the National Academy of Sciences: 116 (7)
Current Issue

Submit

Jump to section

You May Also be Interested in

Nonmonogamous strawberry poison frog (Oophaga pumilio). Image courtesy of Yusan Yang (University of Pittsburgh, Pittsburgh).
Putative signature of monogamy
A study suggests a putative gene-expression hallmark common to monogamous male vertebrates of some species, namely cichlid fishes, dendrobatid frogs, passeroid songbirds, common voles, and deer mice, and identifies 24 candidate genes potentially associated with monogamy.
Image courtesy of Yusan Yang (University of Pittsburgh, Pittsburgh).
Active lifestyles. Image courtesy of Pixabay/MabelAmber.
Meaningful life tied to healthy aging
Physical and social well-being in old age are linked to self-assessments of life worth, and a spectrum of behavioral, economic, health, and social variables may influence whether aging individuals believe they are leading meaningful lives.
Image courtesy of Pixabay/MabelAmber.