The Werner syndrome protein limits the error-prone 8-oxo-dG lesion bypass activity of human DNA polymerase kappa.

[werner syndrome]

Human DNA polymerase kappa (hpol Îº ) is the only Y-family member to preferentially insert dAMP opposite 7 ,8 -dihydro-8 -oxo-2 '-deoxyguanosine (8 -oxo-d G ) during translesion DNA synthesis . We have studied the mechanism of action by which hpol Îº activity is modulated by the Werner syndrome protein (WRN ), a RecQ helicase known to influence repair of 8 -oxo-d G . Here we show that WRN stimulates the 8 -oxo-d G bypass activity of hpol Îº in vitro by enhancing the correct base insertion opposite the lesion , as well as extension from dC :8 -oxo-d G base pairs . Steady-state kinetic analysis reveals that WRN improves hpol Îº-catalyzed dCMP insertion opposite 8 -oxo-d G âˆ¼ 10 -fold and extension from dC :8 -oxo-d G by 2 .4 -fold . Stimulation is primarily due to an increase in the rate constant for polymerization (kpol ), as assessed by pre-steady-state kinetics , and it requires the RecQ C-terminal (RQC ) domain . In support of the functional data , recombinant WRN and hpol Îº were found to physically interact through the exo and RQC domains of WRN , and co -localization of WRN and hpol Îº was observed in human cells treated with hydrogen peroxide . Thus , WRN limits the error-prone bypass of 8 -oxo-d G by hpol Îº , which could influence the sensitivity to oxidative damage that has previously been observed for Werner 's syndrome cells .