A Rad52 homolog is required for RAD51-independent mitotic recombination in Saccharomyces cerevisiae.

Abstract

With the use of an intrachromosomal inverted-repeat as a recombination reporter we have previously shown that mitotic recombination is dependent on the RAD52 gene. However, recombination was found to be reduced only 4-fold by mutation of RAD51, which encodes a homolog of bacterial RecA proteins. A rad51, which strain containing the recombination reporter was mutagenized to identify components of the RAD51-independent pathway. One mutation identified, rad59, reduced recombination 1200-fold in the presence of a rad51 mutation, but only 4-to 5-fold in a wild-type background. Thus the rad51 and rad59 mutations reduce recombination synergistically. The rad59 mutation reduced both spontaneous and double-strand-break-induced recombination between inverted repeats. However, the rate of interchromosomal recombination was increased in a rad59 homozygous diploid. These observations suggest that RAD59 functions specifically in intrachromosomal recombination. The rad59 mutant strain was sensitive to ionizing radiation, and this phenotype was used to clone the RAD59 gene by complementation. The gene encodes a protein of 238 amino acids with significant homology to members of the Rad52 family. Overexpression of RAD52 was found to suppress the DNA repair and recombination defects conferred by the rad59 mutation, suggesting that these proteins have overlapping roles or function as a complex. [Key Words: Recombination; gene conversion; RAD51; RAD52; Saccharomyces cerevisiae]Received April 26, 1996; revised version accepted July 8, 1996.Genes in the RAD52 epistasis group (RAD50-57, XRS2, and MRE11) were identified initially as essential for the repair of ionizing radiation-induced DNA damage or for meiosis (Game and Mortimer 1974;Ajimura et al. 1993). Although the members of this family share the property of conferring resistance to ionizing radiation, they show considerable heterogeneity in other assays for doublestrand break (DSB) repair and recombination. The RAD50, XRS2, and MRE11 genes form a subgroup with similar properties, and interactions between these gene products have been detected by the two-hybrid system (Johzuka and Ogawa 1995). Mutation of other members of this group (RAD51, RAD52, RAD54, RAD55, and RAD5 7) results in the inability to repair DSBs, reduction in spontaneous and induced mitotic recombination, and defects in mating-type switching and sporulation. Of these mutants, rad52 confers the most severe defects in DSB repair and recombination, suggesting that RAD52

Mgm101 Is a Rad52-related Protein Required for Mitochondrial DNA Recombination

“…The eukaryotic Rad52 has retained the SSA activity on its N terminus, but it has also acquired a large C-terminal domain that recruits Rad51 onto ssDNA (38,39). Yeast cells also express Rad59, a Rad52 paralogue that lacks the C-terminal Rad51-interacting domain (40). Rad59 functionally overlaps with Rad52 in DSB repair, but it also appears to have unique functions, including stimulation of Rad52-mediated single strand annealing (41)(42)(43).…”

Rad52 forms ring structures and co‐operates with RPA in single‐strand DNA annealing

“…In recombinations between inverted repeated sequences, a rad51 rad52 double mutant forms the same amount of recombinants as the rad52 single mutant, while the rad51 single mutant yields about 1000-fold more recombinants than the rad52 mutant (Rattray & Symington 1994). Thus, RAD52 function requires most of the recombination reactions in yeasts, and the mutations in the RAD52 gene show pleiotropic phenotypes and confer the most severe defects in recombination and the repair of damaged DNA among genes in the RAD52 epistasis group, including RAD51 (Saeki et al 1980;Rattray & Symington 1994Aguilera 1995;Liefshitz et al 1995;Sugawara et al 1995;Bai & Symington 1996;Malkova et al 1996). The Rad52 protein is known to have an annealing activity for short complementary single-stranded DNAs (Mortensen et al 1996).…”

“…It is composed of at least nine genes: RAD50, - 51,MRE11 and XRS2 (for reviews see Petes et al 1991;Shinohara & Ogawa 1995;Bai & Symington 1996).…”

Physical Interaction between Recombinational Proteins Rhp51 and Rad22 in Schizosaccharomyces pombe

“…These genes, including RAD50, RAD51, RAD52, RAD54, RAD55, RAD57, RPA, MRE11, and XRS2, are well conserved throughout eukaryotes. In addition to these genes, there are several species-specific genes involved in HR, such as RAD59 (4) and RDH54/TID1 (5) in S. cerevisiae, rti1…”