THE FISSION YEAST RAD22 GENE, HAVING A FUNCTION IN MATING-TYPE SWITCHING AND REPAIR OF DNA DAMAGES, ENCODES A PROTEIN HOMOLOG TO RAD52 OF SACCHAROMYCES-CEREVISIAE

The gene rad22 of the fission yeast Schizosaccharomyces pombe has a fu nction in DNA repair and mating-type switching. We have cloned the rad 22 gene from a genomic gene bank by functional complementation of the switching defect. An open reading frame coding for a putative protein of 469 amino acids was found by sequence analyses. The rad22 gene cont ains no intron. A region of 126 amino acids in the N-terminal half of the Rad22 protein has significant homologies (56% identity and 36% sim ilarity) to the Rad52 protein of Saccharomyces cerevisiae. A rad22 dis ruption strain was constructed which seems to be inviable in a homotha llic background. Southern blot analyses have shown that the rad22-67 m utant frequently gives rise to deletions in the mating-type region. Th ese data indicate that the Rad22 protein has a function in the repair of DNA double-strand breaks.