Vital roles of PCNA K165 modification during C. elegans gametogenesis and embryogenesis

In eukaryotes, the DNA damage bypass pathway is promoted by ubiquitylation of PCNA at the conserved lysine 164. Using CRISPR-Cas9 system, we introduced amino acid substitution at K165 of C. elegans PCNA that corresponds to K164 in other characterised organisms and examined the contribution of this residue at a variety of stages during development. In the presence of UV-induced DNA lesions, PCNA-K165 is crucial for not only the early embryonic stages but also during larval development, implicating its functions for a broad time period during animal development. We also show that, without induction of DNA damage, concomitant inhibition of PCNA ubiquitylation and checkpoint activation causes abnormal gametogenesis events and severely impairs reproduction of worms. Our findings suggest a conserved function of PCNA ubiquitylation in tolerance of UV-induced damage and also propose that PCNA ubiquitylation contributes to gametogenesis during unperturbed C. elegans development.