Date Published: September 26, 2018
Publisher: Public Library of Science
Author(s): Masafumi Hayashi, Kenji Keyamura, Takashi Hishida, Marco Muzi-Falconi.
The DNA damage tolerance (DDT) pathway facilitates the bypass of the fork-blocking lesions without removing them through either translesion DNA synthesis or error-free damage bypass mechanism. The Saccharomyces cerevisiae Rad5 is a multi-functional protein involved in the error-free branch of the DDT pathway, and its protein level periodically fluctuates through the cell cycle; however, the mechanistic basis and functional importance of the Rad5 level for the cell cycle regulation remain unclear. Here, we show that Rad5 is predominantly phosphorylated on serine 130 (S130) during S/G2 phase and that this modification depends on the cyclin-dependent kinase Cdc28/CDK1. We also show that the phosphorylated Rad5 species at S130 exhibit a relatively short half-life compared with non-phosphorylated Rad5 moiety, and that the Rad5 protein is partially stabilized in phosphorylation-defective rad5 S130A cells. Importantly, the elimination of this modification results in a defective cell-cycle dependent Rad5 oscillation pattern. Together, our results demonstrate that CDK1 modulates Rad5 stability by phosphorylation during the cell cycle, suggesting a crosstalk between the phosphorylation and degradation of Rad5.
Endogenous and exogenous DNA-damaging agents constantly challenge the integrity of the genome. Eukaryotic organisms have evolved several repair mechanisms that repair DNA damage . However, when replication forks encounter fork-blocking lesions, the resumption of replication only after removal of the fork-blocking lesions would not be practical, as the completion of DNA replication would depend on the repair efficiency. To circumvent this dependency, the DNA damage tolerance (DDT) pathway ensures completion of DNA replication by bypassing unrepaired DNA lesions without removing them, thereby allowing cells to continue growing [2–4].