Werner syndrome (WS), caused by loss of function of the
RecQ helicase WRN, is a
hereditary disease characterized by
premature aging and elevated
cancer incidence. WRN has
DNA binding,
exonuclease,
ATPase, helicase and strand annealing activities, suggesting possible roles in recombination-related processes. Evidence indicates that WRN deficiency causes telomeric abnormalities that likely underlie early onset of aging phenotypes in WS. Furthermore, TRF2, a
protein essential for telomere protection, interacts with WRN and influences its basic helicase and
exonuclease activities. However, these studies provided little insight into WRN's specific function at telomeres. Here, we explored the possibility that WRN and TRF2 cooperate during telomeric recombination processes. Our results indicate that TRF2, through its interactions with both WRN and telomeric
DNA, stimulates WRN-mediated strand exchange specifically between telomeric substrates; TRF2's basic domain is particularly important for this stimulation. Although TRF1 binds telomeric
DNA with similar affinity, it has minimal effects on WRN-mediated strand exchange of telomeric
DNA. Moreover, TRF2 is displaced from telomeric
DNA by WRN, independent of its
ATPase and helicase activities. Together, these results suggest that TRF2 and WRN act coordinately during telomeric recombination processes, consistent with certain telomeric abnormalities associated with alteration of WRN function.