Competition between the Rad50 complex and the Ku heterodimer reveals a role for Exo1 in processing double-strand breaks but not telomeres

被引:124
作者
Tomita, K
Matsuura, A
Caspari, T
Carr, AM
Akamatsu, Y
Iwasaki, H
Mizuno, K
Ohta, K
Uritani, M
Ushimaru, T
Yoshinaga, K
Ueno, M
机构
[1] Shizuoka Univ, Dept Chem, Shizuoka 4228529, Japan
[2] Shizuoka Univ, Dept Biol, Shizuoka 4228529, Japan
[3] Natl Inst Longev Sci, Dept Geriatr Res, Aichi, Japan
[4] Yokohama City Univ, Grad Sch Integrated Sci, Tsurumi Ku, Yokohama, Kanagawa 2300045, Japan
[5] Riken Inst Phys & Chem Res, Genet Dynam Res Unit Lab, Wako, Saitama 3510198, Japan
[6] Univ Sussex, Genome Damage & Stabil Ctr, Brighton BN1 9RQ, E Sussex, England
基金
英国医学研究理事会;
关键词
D O I
10.1128/MCB.23.15.5186-5197.2003
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The Mre11-Rad50-Nbs1(Xrs2) complex and the Ku70-Ku80 heterodimer are thought to compete with each other for binding to DNA ends. To investigate the mechanism underlying this competition, we analyzed both DNA damage sensitivity and telomere overhangs in Schizosaccharomyces pombe rad50-d, rad50-d pku70-d, rad50-d exo1-d, and pku70-d rad50-d exo1-d cells. We found that rad50 exo1 double mutants are more methyl methane sulfonate (MMS) sensitive than the respective single mutants. The MMS sensitivity of rad50-d cells was suppressed by concomitant deletion of pku70(+). However, the MMS sensitivity of the rad50 exo1 double mutant was not suppressed by the deletion of pku70(+). The G-rich overhang at telomere ends in taz1-d cells disappeared upon deletion of rad50(+), but the overhang reappeared following concomitant deletion of pku70(+). Our data suggest that the Rad50 complex can process DSB ends and telomere ends in the presence of the Ku heterodimer. However, the Ku heterodimer inhibits processing of DSB ends and telomere ends by alternative nucleases in the absence of the Rad50-Rad32 protein complex. While we have identified Exo1 as the alternative nuclease targeting DNA break sites, the identity of the nuclease acting on the telomere ends remains elusive.
引用
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页码:5186 / 5197
页数:12
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