Replication fork regression in vitro by the Werner syndrome protein (WRN): Holliday junction formation, the effect of leading arm structure and a potential role for WRN exonuclease activity

Amrita Machwe, Liren Xiao, Robert G. Lloyd, Edward Bolt, David K. Orren

Research output: Contribution to journalArticlepeer-review

51 Scopus citations

Abstract

The premature aging and cancer-prone disease Werner syndrome stems from loss of WRN protein function. WRN deficiency causes replication abnormalities, sensitivity to certain genotoxic agents, genomic instability and early replicative senescence in primary fibroblasts. As a RecQ helicase family member, WRN is a DNA-dependent ATPase and unwinding enzyme, but also possesses strand annealing and exonuclease activities. RecQ helicases are postulated to participate in pathways responding to replication blockage, pathways possibly initiated by fork regression. In this study, a series of model replication fork substrates were used to examine the fork regression capability of WRN. Our results demonstrate that WRN catalyzes fork regression and Holliday junction formation. This process is an ATP-dependent reaction that is particularly efficient on forks containing single-stranded gaps of at least 11-13 nt on the leading arm at the fork junction. Importantly, WRN exonuclease activity, by digesting the leading daughter strand, enhances regression of forks with smaller gaps on the leading arm, thus creating an optimal structure for regression. Our results suggest that the multiple activities of WRN cooperate to promote replication fork regression. These findings, along with the established cellular consequences of WRN deficiency, strongly support a role for WRN in regression of blocked replication forks.

Original languageEnglish
Pages (from-to)5729-5747
Number of pages19
JournalNucleic Acids Research
Volume35
Issue number17
DOIs
StatePublished - Sep 2007

Bibliographical note

Funding Information:
This work was supported by NCI Grant R01 CA113371-01 to D.K.O., while R.G.L. and E.B. were supported by the UK Medical Research Council. The authors would like to thank Joanna Groden, Ken Marians, Steven Matson, Vilhelm Bohr, Judy Campisi and M.D. Gray for providing important reagents and Deanna Edwards for critical reading of the manuscript. Funding to pay the Open Access publication charges for this article was provided by the Graduate Center for Toxicology, University of Kentucky College of Medicine.

ASJC Scopus subject areas

  • Genetics

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