The genetic control of spontaneous and UV-induced mitotic intrachromosomal recombination in the fission yeast Schizosaccharomyces pombe.

An artificially created non-tandem hetero-allelic duplication was constructed to assay mitotic intrachromosomal recombination in Schizosaccharomyces pombe. Two classes of recombinants could be distinguished: deletion-types, in which one copy of the duplicated sequence and the intervening sequence were lost, and conversion-types which retained the duplication. For spontaneous recombination, compared to wild-type cells, a rad22 mutant (corresponding to a Saccharomyces cerevisiae rad52 mutant) had wild-type levels of deletion-types, but was hypo-recombinant for conversion-types; rad16 (S. cerevisiae rad1), rad22 rad16 (S. cerevisiae rad52 rad1) and swi10 (S. cerevisiae rad10) mutants were hyper-recombinant for both types; rad22 swi10 (S. cerevisiae rad52 rad10) mutants were hypo-recombinant for both types; rhp51 (S. cerevisiae rad51) and rhp54 (S. cerevisiae rad54) mutants were hyper-recombinant for deletion-types, but almost completely lacked conversion-types. For wild-type cells, UV-irradiation induced both types of recombinant, but mainly conversion-types. All of the mutants lacked UV-induced recombination.