WRN Interacts Physically and Functionally with the Recombination Mediator Protein RAD52

Kathy Baynton,Marit Otterlei,Magnar Bjørås,Cayetano Von Kobbe,Vilhelm A Bohr,Erling Seeberg

doi:10.1074/jbc.m303885200

Abstract

Werner syndrome (WS) is a premature aging disorder that predisposes affected individuals to cancer development. The affected gene, WRN, encodes an RecQ homologue whose precise biological function remains elusive. Altered DNA recombination is a hallmark of WS cells suggesting that WRN plays an important role in these pathways. Here we report a novel physical and functional interaction between WRN and the homologous recombination mediator protein RAD52. Fluorescence resonance energy transfer (FRET) analyses show that WRN and RAD52 form a complex in vivo that co-localizes in foci associated with arrested replication forks. Biochemical studies demonstrate that RAD52 both inhibits and enhances WRN helicase activity in a DNA structure-dependent manner, whereas WRN increases the efficiency of RAD52-mediated strand annealing between non-duplex DNA and homologous sequences contained within a double-stranded plasmid. These results suggest that coordinated WRN and RAD52 activities are involved in replication fork rescue after DNA damage.

Highlights

Werner syndrome (WS) is a premature aging disorder that predisposes affected individuals to cancer development
Neither WRN C terminus (WRN-C) nor RAD52 co-transfected with the corresponding empty binding domain constructs (BD) and AD vectors, respectively, produced colonies on ϪHIS media
This work describes for the first time, a physical and functional interaction between WRN and a poorly understood component of the human Homologous recombination (HR) machinery, the recombination mediator protein RAD52

Summary

Introduction

Werner syndrome (WS) is a premature aging disorder that predisposes affected individuals to cancer development. Biochemical studies demonstrate that RAD52 both inhibits and enhances WRN helicase activity in a DNA structuredependent manner, whereas WRN increases the efficiency of RAD52-mediated strand annealing between non-duplex DNA and homologous sequences contained within a double-stranded plasmid. These results suggest that coordinated WRN and RAD52 activities are involved in replication fork rescue after DNA damage. Cells from Werner syndrome (WS) patients exhibit elevated genome instability manifested as telomere defects, and chromosomal translocations and large deletions [6, 7, 8] The latter rearrangements are thought to reflect aberrant DNA recombination, a process responsible for the repair of single strand gaps and double strand breaks (DSBs). Homologous recombination (HR) corrects strand breaks using homologous sequences primarily from the sister chromatid and, to a lesser extent, from the chromosome homologue [12, 13]; it is a high fidelity repair mechanism

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Conclusion