A conserved Ctp1/CtIP C-terminal peptide stimulates Mre11 endonuclease activity

The Mre11-Rad50-Nbs1 complex (MRN) is important for repairing DNA double-strand breaks (DSBs) by homologous recombination (HR). The endonuclease activity of MRN is critical for resecting 5′-ended DNA strands at DSB ends, producing 3′-ended single-strand DNA, a prerequisite for HR. This endonuclease activity is stimulated by Ctp1, the Schizosaccharomyces pombe homolog of human CtIP. Here, with purified proteins, we show that Ctp1 phosphorylation stimulates MRN endonuclease activity by inducing the association of Ctp1 with Nbs1. The highly conserved extreme C terminus of Ctp1 is indispensable for MRN activation. Importantly, a polypeptide composed of the conserved 15 amino acids at the C terminus of Ctp1 (CT15) is sufficient to stimulate Mre11 endonuclease activity. Furthermore, the CT15 equivalent from CtIP can stimulate human MRE11 endonuclease activity, arguing for the generality of this stimulatory mechanism. Thus, we propose that Nbs1-mediated recruitment of CT15 plays a pivotal role in the activation of the Mre11 endonuclease by Ctp1/CtIP.

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CTCF cooperates with CtIP to drive homologous recombination repair of double-strand breaks

Nucleic Acids Research ◽

10.1093/nar/gkz639 ◽

2019 ◽

Vol 47 (17) ◽

pp. 9160-9179 ◽

Cited By ~ 6

Author(s):

Soon Young Hwang ◽

Mi Ae Kang ◽

Chul Joon Baik ◽

Yejin Lee ◽

Ngo Thanh Hang ◽

...

Keyword(s):

Homologous Recombination ◽

Critical Role ◽

Control Point ◽

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

Strand Breaks ◽

C Terminus ◽

Dna End Resection ◽

End Resection

Abstract The pleiotropic CCCTC-binding factor (CTCF) plays a role in homologous recombination (HR) repair of DNA double-strand breaks (DSBs). However, the precise mechanistic role of CTCF in HR remains largely unclear. Here, we show that CTCF engages in DNA end resection, which is the initial, crucial step in HR, through its interactions with MRE11 and CtIP. Depletion of CTCF profoundly impairs HR and attenuates CtIP recruitment at DSBs. CTCF physically interacts with MRE11 and CtIP and promotes CtIP recruitment to sites of DNA damage. Subsequently, CTCF facilitates DNA end resection to allow HR, in conjunction with MRE11–CtIP. Notably, the zinc finger domain of CTCF binds to both MRE11 and CtIP and enables proficient CtIP recruitment, DNA end resection and HR. The N-terminus of CTCF is able to bind to only MRE11 and its C-terminus is incapable of binding to MRE11 and CtIP, thereby resulting in compromised CtIP recruitment, DSB resection and HR. Overall, this suggests an important function of CTCF in DNA end resection through the recruitment of CtIP at DSBs. Collectively, our findings identify a critical role of CTCF at the first control point in selecting the HR repair pathway.

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Coordinated nuclease activities counteract Ku at single-ended DNA double-strand breaks

Nature Communications ◽

10.1038/ncomms12889 ◽

2016 ◽

Vol 7 (1) ◽

Cited By ~ 56

Author(s):

Pauline Chanut ◽

Sébastien Britton ◽

Julia Coates ◽

Stephen P. Jackson ◽

Patrick Calsou

Keyword(s):

Homologous Recombination ◽

Mammalian Cells ◽

Double Strand Breaks ◽

Exonuclease Activity ◽

Endonuclease Activity ◽

Dna Double Strand Breaks ◽

Additional Mechanism ◽

Strand Breaks ◽

Rad51 Focus ◽

Dna Resection

Abstract Repair of single-ended DNA double-strand breaks (seDSBs) by homologous recombination (HR) requires the generation of a 3′ single-strand DNA overhang by exonuclease activities in a process called DNA resection. However, it is anticipated that the highly abundant DNA end-binding protein Ku sequesters seDSBs and shields them from exonuclease activities. Despite pioneering works in yeast, it is unclear how mammalian cells counteract Ku at seDSBs to allow HR to proceed. Here we show that in human cells, ATM-dependent phosphorylation of CtIP and the epistatic and coordinated actions of MRE11 and CtIP nuclease activities are required to limit the stable loading of Ku on seDSBs. We also provide evidence for a hitherto unsuspected additional mechanism that contributes to prevent Ku accumulation at seDSBs, acting downstream of MRE11 endonuclease activity and in parallel with MRE11 exonuclease activity. Finally, we show that Ku persistence at seDSBs compromises Rad51 focus assembly but not DNA resection.

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Faculty Opinions recommendation of Transcriptionally active chromatin recruits homologous recombination at DNA double-strand breaks.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.718321312.793493797 ◽

2014 ◽

Author(s):

Vijay Tiwari ◽

Sandra Schick

Keyword(s):

Homologous Recombination ◽

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

Active Chromatin ◽

Strand Breaks

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Analysis of chromatid-break-repair detects a homologous recombination to non-homologous end-joining switch with increasing load of DNA double-strand breaks

Mutation Research/Genetic Toxicology and Environmental Mutagenesis ◽

10.1016/j.mrgentox.2021.503372 ◽

2021 ◽

pp. 503372

Author(s):

Tamara Murmann-Konda ◽

Aashish Soni ◽

Martin Stuschke ◽

George Iliakis

Keyword(s):

Homologous Recombination ◽

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

End Joining ◽

Strand Breaks ◽

Chromatid Break ◽

Break Repair ◽

Non Homologous End Joining ◽

Increasing Load

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

Biochemical Society Transactions ◽

10.1042/bst20120307 ◽

2013 ◽

Vol 41 (1) ◽

pp. 314-320 ◽

Cited By ~ 30

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.

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Genetic Separation of Sae2 Nuclease Activity from Mre11 Nuclease Functions in Budding Yeast

Molecular and Cellular Biology ◽

10.1128/mcb.00156-17 ◽

2017 ◽

Vol 37 (24) ◽

Cited By ~ 8

Author(s):

Sucheta Arora ◽

Rajashree A. Deshpande ◽

Martin Budd ◽

Judy Campbell ◽

America Revere ◽

...

Keyword(s):

Nuclease Activity ◽

Double Strand Breaks ◽

Endonuclease Activity ◽

Dna Double Strand Breaks ◽

Dna Breaks ◽

Content Type ◽

Strand Breaks ◽

Dna Ends

ABSTRACT Sae2 promotes the repair of DNA double-strand breaks in Saccharomyces cerevisiae. The role of Sae2 is linked to the Mre11/Rad50/Xrs2 (MRX) complex, which is important for the processing of DNA ends into single-stranded substrates for homologous recombination. Sae2 has intrinsic endonuclease activity, but the role of this activity has not been assessed independently from its functions in promoting Mre11 nuclease activity. Here we identify and characterize separation-of-function mutants that lack intrinsic nuclease activity or the ability to promote Mre11 endonucleolytic activity. We find that the ability of Sae2 to promote MRX nuclease functions is important for DNA damage survival, particularly in the absence of Dna2 nuclease activity. In contrast, Sae2 nuclease activity is essential for DNA repair when the Mre11 nuclease is compromised. Resection of DNA breaks is impaired when either Sae2 activity is blocked, suggesting roles for both Mre11 and Sae2 nuclease activities in promoting the processing of DNA ends in vivo. Finally, both activities of Sae2 are important for sporulation, indicating that the processing of meiotic breaks requires both Mre11 and Sae2 nuclease activities.

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