Ubiquitin protease Ubp1 cooperates with Ubp10 and Ubp12 to revert Lysine-164 PCNA ubiquitylation at replication forks

Abstract

[EN]Proliferating cell nuclear antigen (PCNA) is essential for the faithful duplication of eukaryotic genomes. PCNA also orchestrates events necessary to deal with threats to genomic integrity, such as the DNA damage tolerance (DDT) response, a mechanism by which eukaryotic cells bypass replication-blocking lesions to maintain replisome stability. DDT is regulated by the ubiquitylation of PCNA and the consequent recruitment of specialized polymerases that guarantee the continuity of replication. We have recently described that the deubiquitylases Ubp10 and Ubp12 modulate DDT events by reverting the ubiquitylation of PCNA in Saccharomyces cerevisiae. This study unveils Ubp1 as a new PCNA deubiquitylase, which cooperates with Ubp10 and Ubp12 in the regulation of DDT during DNA replication. Ubp1, so far known as a cytoplasmic protein, also localizes to the nucleus where associates with DNA replication forks. In addition, Ubp1 interacts with and deubiquitylates PCNA. Importantly, we provide the first evidence that S. cerevisiae PCNA is ubiquitylated during an unperturbed S phase and that Ubp1, Ubp10, and Ubp12 work together facilitating DNA replication by efficiently reverting PCNA ubiquitylation at replication forks. Thus, the ablation of Ubp1, Ubp10, and Ubp12 causes a permanent ubiquitylation of PCNA and a marked delay in the S phase progression.