期刊
CELL
卷 134, 期 6, 页码 981-994出版社
CELL PRESS
DOI: 10.1016/j.cell.2008.08.037
关键词
-
资金
- NIH [GM80600-02, GM071011]
- Texas Advanced Research Program
- [GM20056]
Formation of single-strand DNA (ssDNA) tails at a double-strand break (DSB) is a key step in homologous recombination and DNA-damage signaling. The enzyme(s) producing ssDNA at DSBs in eukaryotes remain unknown. We monitored 5'-strand resection at inducible DSB ends in yeast and identified proteins required for two stages of resection: initiation and long-range 50-strand resection. We show that the Mre11-Rad50-Xrs2 complex (MRX) initiates 50 degradation, whereas Sgs1 and Dna2 degrade 50 strands exposing long 30 strands. Deletion of SGS1 or DNA2 reduces resection and DSB repair by single-strand annealing between distant repeats while the remaining long-range resection activity depends on the exonuclease Exo1. In exo1 Delta sgs1 Delta double mutants, the MRX complex together with Sae2 nuclease generate, in a stepwise manner, only few hundred nucleotides of ssDNA at the break, resulting in inefficient gene conversion and G2/M damage checkpoint arrest. These results provide important insights into the early steps of DSB repair in eukaryotes.
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