Mre11 regulates CtIP-dependent double-strand break repair by interaction with CDK2

Abstract

Homologous recombination (HR) facilitates accurate repair of DNA double strand breaks (DSBs) during S and G2 phases of the cell cycle by using intact sister chromatids as sequence templates. HR capacity is maximized in S and G2 by Cyclin–Dependent Kinase (CDK) phosphorylation of CtIP, which subsequently interacts with BRCA1 and the Mre11–Rad50–NBS1 (MRN) complex. Here we show that Mre11 controls these events through a direct interaction with CDK2 that is required for CtIP phosphorylation and BRCA1 interaction in normally dividing cells. CDK2 binds the C–terminus of Mre11, which is absent in an inherited allele causing Ataxia–Telangiectasia Like Disorder. This newly uncovered role for Mre11 does not require ATM activation or nuclease activities. Therefore, functions of MRN are not restricted to DNA damage responses, but include regulating HR capacity during the normal mammalian cell cycle.

End Resection at Double-Strand Breaks: Mechanism and Regulation

“…Interestingly, addition of an nuclear localization signal (NLS) to Mre11 can partially suppress the DNA damage sensitivity of the xrs2D mutant, indicating that one of the main functions for Xrs2 is Mre11 localization to the nucleus (Tsukamoto et al 2005). The carboxyterminal 54 residues of murine Mre11 interact with cyclin-dependent kinase 2 (CDK2) to facilitate CtIP phosphorylation and stability (Buis et al 2012). Rad50 has a similar domain organization to the structural maintenance of chromosomes family of proteins, which are characterized by Walker A and B ATP-binding cassettes located at the amino-and carboxy-terminal regions of the primary sequence that come together by collapse of the intervening sequence to form a long antiparallel coiled-coil ( Fig.…”

The same, only different – DNA damage checkpoints and their reversal throughout the cell cycle

“…This activation of ATR and Chk1 kinases also occurs as a consequence of replication, when the replication fork generates single-strand DNA (ssDNA) (Paulsen and Cimprich, 2007). Cdk2 phosphorylates the key exonucleases CtIP (also known as RBBP8) and Exo1 to enable DNA endresection and ensure that end-resection occurs only after S-phase entry (Buis et al, 2012;Tomimatsu et al, 2014;Wang et al, 2013). In addition, Cdk2-dependent, activating phosphorylations of the ATR-interacting protein ATRIP (at S224) and Chk1 itself (at S286 and S301) further restrict full activation of ATR and Chk1 to S-and G2-phase (Myers et al, 2007;Xu et al, 2012).…”

When two is not enough: a CtIP tetramer is required for DNA repair by Homologous Recombination

“…8,9 The critical function of CtIP/Ctp1/Sae2 at DNA ends is carried out in close functional and physical cooperation with the DNA damage sensor and repair complex MRE11-RAD50-NBS1 (MRN, where NBS1 is Xrs2 in budding yeast). [10][11][12][13][14][15] The central role of CtIP/Ctp1/Sae2 in DSB repair is further highlighted by its complex regulation, mediated by an array of post-translational modifications that include phosphorylation by cyclin-dependent and DNA-damage activated kinases, acetylation, ubiquitylation, NEDDylation and proline isomerisation. 3 Despite its importance to DSB repair, our mechanistic understanding of how CtIP promotes resection remains incomplete.…”