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PMID: 15616582 Published · ppublish English Journal Article Research Support, Non-U.S. Gov't

Mechanistically distinct roles for Sgs1p in checkpoint activation and replication fork maintenance.

The EMBO journal ·Vol. 24 ·No. 2 ·2005-01-26 ·Pages 405-17

Bjergbaek L, Cobb JA, Tsai-Pflugfelder M, Gasser SM

Abstract

The RecQ helicase Sgs1p forms a complex with the type 1 DNA topoisomerase Top3p that resolves double Holliday junctions resulting from Rad51-mediated exchange. We find, however, that Sgs1p functions independently of both Top3p and Rad51p to stimulate the checkpoint kinase Rad53p when replication forks stall due to dNTP depletion on hydroxyurea. Checkpoint activation does not require Sgs1p function as a helicase, and correlates with its ability to bind the Rad53p kinase FHA1 motif directly. On the other hand, Sgs1p's helicase activity is required together with Top3p and the strand-exchange factor Rad51p, to help stabilise DNA polymerase epsilon at stalled replication forks. In this function, the Sgs1p/Top3p complex acts in parallel to the Claspin-related adaptor, Mrc1p, although the sgs1 and mrc1 mutations are epistatic for Rad53p activation. We thus identify two distinct pathways through which Sgs1p contributes to genomic integrity: checkpoint kinase activation requires Sgs1p as a noncatalytic Rad53p-binding site, while the combined Top3p/Sgs1p resolvase activity contributes to replisome stability and recovery from arrested replication forks.

MeSH Terms
Cell Cycle Cell Cycle Proteins/physiology Checkpoint Kinase 2 DNA Helicases/physiology DNA Replication DNA Topoisomerases, Type I/physiology Hydroxyurea/pharmacology Immunoprecipitation Phosphorylation Protein Serine-Threonine Kinases/physiology RecQ Helicases Saccharomyces cerevisiae Proteins/physiology Two-Hybrid System Techniques
Chemicals
Cell Cycle Proteins Saccharomyces cerevisiae Proteins Checkpoint Kinase 2 Protein Serine-Threonine Kinases RAD53 protein, S cerevisiae SGS1 protein, S cerevisiae DNA Helicases RecQ Helicases DNA Topoisomerases, Type I Hydroxyurea
Authors & Affiliations
4 authors, click to expand affiliations / ORCID
Bjergbaek Lotte
Department of Molecular Biology and NCCR, Frontiers in Genetics, University of Geneva, Quai Ernest-Ansermet 30, Geneva, Switzerland.
Cobb Jennifer A
Tsai-Pflugfelder Monica
Gasser Susan M
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Article Info
Journal
The EMBO journal
Abbr.
EMBO J
ISSN
0261-4189
DOI
10.1038/sj.emboj.7600511
Published
2005-01-26
Epub
2004-00-23
Pages
405-17
Language
English
Region
England
NLM ID
8208664
PMCID
PMC545806
Subset
IM
Grants
NCCDPHP CDC HHS · U48 DP000060 · United States
External Links
PubMed source DOI: 10.1038/sj.emboj.7600511 PMC Full Text View journal details
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