Mating-type suppression of the DNA-repair defect of the yeast rad6Δ mutation requires the activity of genes in the RAD52 epistasis group

The RAD6 gene of Saccharomyces cerevisiae is required for post-replication repair of UV-damaged DNA, UV mutagenesis, and sporulation. Here, we show that the radiation sensitivity of a MATarad6Δ strain can be suppressed by the MATα2 gene carried on a multicopy plasmid. The a1-α2 suppression is specific to the RAD6 pathway, as mutations in genes required for nucleotide excision repair or for recombinational repair do not show such mating-type suppression. The a1-α2 suppression of the rad6Δ mutation requires the activity of the RAD52 group of genes, suggesting that suppression occurs by channelling of post-replication gaps present in the rad6Δ mutant into the RAD52 recombinational repair pathway. The a1-α2 repressor could mediate this suppression via an enhancement in the expression, or the activity, of recombination genes.