Affiliation:
1. Cancer Research UK Drug-DNA Interactions Research Group, Department of Oncology, Royal Free and University College Medical School, University College London, London
2. Cancer Research UK Laboratories, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
Abstract
ABSTRACT
Pso2/Snm1 is a member of the β-CASP metallo-β-lactamase family of proteins that include the V(D)J recombination factor Artemis.
Saccharomyces cerevisiae pso2
mutants are specifically sensitive to agents that induce DNA interstrand cross-links (ICLs). Here we establish a novel overlapping function for
PSO2
with MutS mismatch repair factors and the 5′-3′ exonuclease Exo1 in the repair of DNA ICLs, which is confined to S phase. Our data demonstrate a requirement for NER and Pso2, or Exo1 and MutS factors, in the processing of ICLs, and this is required prior to the repair of ICL-induced DNA double-strand breaks (DSBs) that form during replication. Using a chromosomally integrated inverted-repeat substrate, we also show that loss of both
pso2
and
exo1/msh2
reduces spontaneous homologous recombination rates. Therefore,
PSO2
,
EXO1
, and
MSH2
also appear to have overlapping roles in the processing of some forms of endogenous DNA damage that occur at an irreversibly collapsed replication fork. Significantly, our analysis of ICL repair in cells synchronized for each cell cycle phase has revealed that homologous recombination does not play a major role in the direct repair of ICLs, even in G
2
, when a suitable template is readily available. Rather, we propose that recombination is primarily involved in the repair of DSBs that arise from the collapse of replication forks at ICLs. These findings have led to considerable clarification of the complex genetic relationship between various ICL repair pathways.
Publisher
American Society for Microbiology
Subject
Cell Biology,Molecular Biology
Cited by
65 articles.
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