(A-D) Effect of rad52∆, rad51∆ (A), rad57∆ (B) and rad54∆ (C) on PCNA ubiquitylation in cells synchronized in G1 and released into fresh medium in the presence of 0.025% MMS. Cell cycle progression was followed by cell sorting analysis and western blot against Clb2. Pgk1 was used as loading control. The amounts of mono- and polyubiquitylated PCNA were normalized to the total amount of PCNA. For each time point, rad mutant values were relativized to those of the wild type, taken as 1. The mean and SEM of 3 independent experiments are shown (D). An asterisk indicates a mean significantly different than 1, according to a One-sample t-test. 