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Phosphorylated CtIP functions as a co-factor of the MRE11-RAD50-NBS1 endonuclease in DNA end resection


Anand, Roopesh; Ranjha, Lepakshi; Cannavo, Elda; Cejka, Petr (2016). Phosphorylated CtIP functions as a co-factor of the MRE11-RAD50-NBS1 endonuclease in DNA end resection. Molecular Cell, 64(1):940-950.

Abstract

To repair a DNA double-strand break (DSB) by homologous recombination (HR), the 5'-terminated strand of the DSB must be resected. The human MRE11-RAD50-NBS1 (MRN) and CtIP proteins were implicated in the initiation of DNA end resection, but the underlying mechanism remained undefined. Here, we show that CtIP is a co-factor of the MRE11 endonuclease activity within the MRN complex. This function is absolutely dependent on CtIP phosphorylation that includes the key cyclin-dependent kinase target motif at Thr-847. Unlike in yeast, where the Xrs2/NBS1 subunit is dispensable in vitro, NBS1 is absolutely required in the human system. The MRE11 endonuclease in conjunction with RAD50, NBS1, and phosphorylated CtIP preferentially cleaves 5'-terminated DNA strands near DSBs. Our results define the initial step of HR that is particularly relevant for the processing of DSBs bearing protein blocks.

Abstract

To repair a DNA double-strand break (DSB) by homologous recombination (HR), the 5'-terminated strand of the DSB must be resected. The human MRE11-RAD50-NBS1 (MRN) and CtIP proteins were implicated in the initiation of DNA end resection, but the underlying mechanism remained undefined. Here, we show that CtIP is a co-factor of the MRE11 endonuclease activity within the MRN complex. This function is absolutely dependent on CtIP phosphorylation that includes the key cyclin-dependent kinase target motif at Thr-847. Unlike in yeast, where the Xrs2/NBS1 subunit is dispensable in vitro, NBS1 is absolutely required in the human system. The MRE11 endonuclease in conjunction with RAD50, NBS1, and phosphorylated CtIP preferentially cleaves 5'-terminated DNA strands near DSBs. Our results define the initial step of HR that is particularly relevant for the processing of DSBs bearing protein blocks.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Institute of Molecular Cancer Research
07 Faculty of Science > Institute of Molecular Cancer Research
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Language:English
Date:4 November 2016
Deposited On:08 Dec 2016 14:31
Last Modified:02 Feb 2018 10:49
Publisher:Cell Press (Elsevier)
ISSN:1097-2765
OA Status:Closed
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1016/j.molcel.2016.10.017
PubMed ID:27889449

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