Differential and Concordant Roles for Poly(ADP-Ribose) Polymerase 1 and Poly(ADP-Ribose) in Regulating WRN and RECQL5 Activities

Abstract

Poly(ADP-ribose) (PAR) polymerase 1 (PARP1) catalyzes the poly(ADP-ribosyl)ation (PARylation) of proteins, a posttranslational modification which forms the nucleic acid-like polymer PAR. PARP1 and PAR are integral players in the early DNA damage response, since PARylation orchestrates the recruitment of repair proteins to sites of damage. Human RecQ helicases are DNA unwinding proteins that are critical responders to DNA damage, but how their recruitment and activities are regulated by PARPs and PAR is poorly understood. Here we report that all human RecQ helicases interact with PAR noncovalently. Furthermore, we define the effects that PARP1, PARylated PARP1, and PAR have on RECQL5 and WRN, using both in vitro and in vivo assays. We show that PARylation is involved in the recruitment of RECQL5 and WRN to laser-induced DNA damage and that RECQL5 and WRN have differential responses to PARylated PARP1 and PAR. Furthermore, we show that the loss of RECQL5 or WRN resulted in increased sensitivity to PARP inhibition. In conclusion, our results demonstrate that PARP1 and PAR actively, and in some instances differentially, regulate the activities and cellular localization of RECQL5 and WRN, suggesting that PARylation acts as a fine-tuning mechanism to coordinate their functions in time and space during the genotoxic stress response.

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.00427-15.

ACKNOWLEDGMENTS

HeLa PARP1^−/− cells were a gift from Elisa Ferrando-May and Alexander Bürkle (University of Konstanz). We thank Xiao-Fan Wang from Duke University for the U2OS DR/GFP cell line and V. Gorbunova from the University of Rochester for the HCA2 NHEJ-I9A cell line. We thank Thomasz Kulikowicz for the recombinant dually tagged WRN proteins. We thank Beverly Baptise and Jaya Sarkar for reading and providing helpful comments on the manuscript.

This work was supported in part by the Intramural Research Program of the National Institutes of Health, National Institute on Aging. S.V. was supported by a fellowship of DFG-funded research training group 1331.