Disruptions of the Ustilago maydis REC2 gene identify a protein domain important in directing recombinational repair of DNA

The REC2 gene of Ustilago maydis encodes a homologue of the Escherichia col i RecA protein and was first identified in a screen for UV-sensitive mutant s. The original isolate, rec2-1, was found to be deficient in repair of DNA damage, genetic recombination and meiosis. We report here that the rec2-19 7 allele, which was constructed by gene disruption, retains some biological activity and is partially dominant with respect to REC2. The basis for the residual activity is probably as a result of expression of a diffusible pr oduct from the rec2-197 allele that augments or interferes with REC2 functi ons. This product appears to be a polypeptide expressed from a remnant of t he 5' end of the open reading frame that was not removed in creating the ge ne disruption. The mutator activity and disturbed meiosis of rec2-197 sugge st that the Rec2 protein functions in a process that avoids spontaneous mut ation and insures faithful meiotic chromosome segregation. A prediction bas ed on the phenotype of rec2-197 is that Rec2 protein interacts with one or more other proteins in directing these functions. To identify interacting p roteins we performed a yeast two-hybrid screen and found Rad51 as a candida te. Rec2-197 and Rad51 appear to interact to a similar degree.