DLH1, the Candida albicans homologue of the meiosis-specific DMC1, is not involved in DNA repair but catalyses spontaneous interhomologue recombination and might promote non-crossover events

摘要

DLH1, the Candida albicans orthologue of the meiosis-specific recombinase DMC1 was expressed during the mitotic cycle. In contrast to rad51-Delta Delta that displayed reduced growth rate and severe susceptibility to DNA-damaging agents, dlh1-Delta Delta behaved as wild type (WT), rad51-Delta Delta being was epistatic to dlh1-Delta Delta. However, dlh1-Delta Delta showed an increased frequency of spontaneous loss-of-heterozygosity (LOH) at the HIS4/his4 (Chr4) locus. For both WT and dlh1-Delta Delta, His auxotrophs arose via Chr4 loss and interhomologue recombination whereas rad51-Delta Delta and rad51-Delta Delta dlh1-Delta Delta His(-) segregants were formed mainly by chromosome loss and truncation. A few rad51-Delta Delta, but not rad51-Delta Delta dlh1-Delta Delta, segregants showed interhomologue recombination. LOH events at the GAL1/URA3 locus (Chr1; URA3 substitutes one GAL1 allele) in WT and dlh1-Delta Delta involved mainly long tracts of DNA. A few short-tract LOH events were detected in WT but not in dlh1-Delta Delta, and this dlh1-Delta Delta phenotype was partially complemented by a WT DLH1 allele. Long-tract LOH events were also predominant in rad51-Delta Delta, but about half of them arose via chromosome truncation. We suggest that Dlh1, which conserves the Dmc1 lineage-specific amino acid residues, can promote strand invasion and might regulate in combination with Rad51 the length of the conversion tracts and the relative frequencies of mitotic non-crossovers in C. albicans.