title: Functional differences and interactions among the putative RecA homologs Rad51, Rad55, and Rad57.
abstract: The genes of the Saccharomyces cerevisiae RAD52 epistasis group are required for the repair of ionizing radiation-induced DNA damage. Three of these genes, RAD51, RAD55, and RAD57, have been identified as putative RecA homologs. An important feature of RecA is its ability to bind and hydrolyze ATP. RAD55 and RAD57 contain putative nucleotide binding motifs, and the importance of these motifs was determined by constructing site-directed mutations of the conserved lysine residue within the Walker A-box. Changing the lysine residue to arginine or alanine resulted in a mutant phenotype in DNA repair and sporulation for Rad55 but not for Rad57. Protein-protein interactions among Rad51, Rad55, and Rad57 were tested for by the two-hybrid system. Rad55 was shown to interact with Rad51 and Rad57 but not with itself. Additionally, no interaction between Rad57 and Rad51 or between Rad57 and itself was detected. Consistent with the hypothesis that Rad55 and Rad57 may function within, or stabilize, a protein complex, we found that RAD51 expressed from a high-copy-number plasmid suppresses the DNA repair defect of strains carrying rad55 and rad57 mutations. These data, in conjunction with other reports, demonstrate the importance of protein-protein interactions in the process of DNA repair.
authors.affiliation: Department of Microbiology, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA.
authors.forename: R D
authors.initials: RD
authors.lastname: Johnson
authors.forename: L S
authors.initials: LS
authors.lastname: Symington
mesh_terms: D000251:Adenosine Triphosphatases; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D004260:DNA Repair / Q000235:genetics*; D045643:DNA Repair Enzymes; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D005720:Gamma Rays; D018628:Gene Dosage; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D051135:Rad51 Recombinase; D011938:Rec A Recombinases / Q000235:genetics; D011994:Recombinant Proteins / Q000378:metabolism; D012098:Reproduction / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000528:radiation effects; D029701:Saccharomyces cerevisiae Proteins; D017385:Sequence Homology; D013489:Suppression, Genetic
chemical_list: D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C087191:RAD55 protein, S cerevisiae; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; C495151:RAD51 protein, S cerevisiae; D051135:Rad51 Recombinase; D011938:Rec A Recombinases; D000251:Adenosine Triphosphatases; C071451:RAD57 protein, S cerevisiae; D045643:DNA Repair Enzymes