PCNA Deubiquitylases Control DNA Damage Bypass at Replication Forks

Abstract

Summary: DNA damage tolerance plays a key role in protecting cell viability through translesion synthesis and template switching-mediated bypass of genotoxic polymerase-blocking base lesions. Both tolerance pathways critically rely on ubiquitylation of the proliferating-cell nuclear antigen (PCNA) on lysine 164 and have been proposed to operate uncoupled from replication. We report that Ubp10 and Ubp12 ubiquitin proteases differentially cooperate in PCNA deubiquitylation, owing to distinct activities on PCNA-linked ubiquitin chains. Ubp10 and Ubp12 associate with replication forks in a fashion determined by Ubp10 dependency on lagging-strand PCNA residence, and they downregulate translesion polymerase recruitment and template switch events engaging nascent strands. These findings reveal PCNAK164 deubiquitylation as a key mechanism for the modulation of lesion bypass during replication, which might set a framework for establishing strand-differential pathway choices. We propose that damage tolerance is tempered at replication forks to limit the extension of bypass events and sustain chromosome replication rates. : Álvarez et al. reveal a mechanism that modulates DNA damage tolerance to promote processive DNA synthesis. Ubp10 and Ubp12 ubiquitin proteases bind replication forks and distinctly cooperate to revert the ubiquitylation of the essential replication factor PCNA at lysine 164, hence restraining DNA damage tolerance events engaging nascent strands. Keywords: cell cycle, DNA replication, replication forks, PCNA, ubiquitin-proteases, DNA damage tolerance