Open AccessFunctional Interplay of the Mre11 Nuclease and Ku in the Response to Replication-Associated DNA Damage
Author(s) -
Steven S. Foster,
Alessia Balestrini,
John H.J. Petrini
Publication year - 2011
Publication title -
molecular and cellular biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.14
H-Index - 327
eISSN - 1067-8824
pISSN - 0270-7306
DOI - 10.1128/mcb.05854-11
Subject(s) - biology , nuclease , dna damage , ku70 , ku80 , replication protein a , dna , dna repair , microbiology and biotechnology , dna replication , methyl methanesulfonate , non homologous end joining , mutant , genetics , dna binding protein , gene , transcription factor
The Mre11 complex is a central component of the DNA damage response, with roles in damage sensing, molecular bridging, and end resection. We have previously shown that inSaccharomyces cerevisiae , Ku70 (yKu70) deficiency reduces the ionizing radiation sensitivity ofmre11 Δ mutants. In this study, we show that yKu70 deficiency suppressed the camptothecin (CPT) and methyl methanesulfonate (MMS) sensitivity of nuclease-deficientmre11 -3 andsae2Δ mutants in an Exo1-dependent manner. CPT-induced G2 /M arrest, γ-H2AX persistence, and chromosome breaks were elevated inmre11 -3 mutants. These outcomes were reduced by yKu70 deficiency. Given that the genotoxic effects of CPT are manifest during DNA replication, these data suggest that Ku limits Exo1-dependent double-strand break (DSB) resection during DNA replication, inhibiting the initial processing steps required for homology-directed repair. We propose that Mre11 nuclease- and Sae2-dependent DNA end processing, which initiates DSB resection prevents Ku from engaging DSBs, thus promoting Exo1-dependent resection. In agreement with this idea, we show that Ku affinity for binding to short single-stranded overhangs is much lower than for blunt DNA ends. Collectively, the data define a nonhomologous end joining (NHEJ)-independent, S-phase-specific function of the Ku heterodimer.