Rtt105 configurationally staples RPA and blocks facilitated exchange and interactions with RPA-interacting proteins

Abstract

Replication Protein A (RPA) binds to single-stranded DNA (ssDNA) and recruits over three dozen RPA-interacting proteins (RIPs) to coordinate multiple aspects of DNA metabolism in-cluding DNA replication, repair, and recombination. Rtt105 is a molecular chaperone that regu-lates nuclear localization of RPA. Whether and how Rtt105 regulates the activities of RPA is poorly understood. Here, we show that Rtt105 binds to multiple DNA binding and protein-interaction domains of RPA and configurationally staples the complex. In the absence of ssDNA, Rtt105 inhibits RPA binding to Rad52, thus preventing spurious binding to RPA-interacting pro-teins (RIPs). When ssDNA is available, Rtt105 promotes formation of high-density RPA nucleo-protein filaments and dissociates during this process. Free Rtt105 further stabilizes the RPA-ssDNA filaments by inhibiting RPA facilitated exchange. Collectively, our data suggest that Rtt105 sequesters free RPA in the nucleus to prevent untimely RIP interaction, while stabilizing RPA-ssDNA filaments at DNA lesion sites.

Competing Interest Statement

The authors have declared no competing interest.