Rad51, a 37 kDa protein, is the human homologue of E. coli RecA protein and a member of the RAD52 epistasis group in S. cerevisiae. In recent studies it has been reported that BRCA1 interacts with Rad51 and disease-causing mutations have been found in the BRCA1 region necessary for BRCA1/Rad51 interaction, implying that this interaction is important for tumor suppression. BRCA2 and Rad51 have also been shown to interact by direct binding of the BRC repeats located within exon 11 of BRCA2. When these repeats are deleted, the interaction is lost and cells become hypersensitive to the DNA damage caused by methyl methanesulfonate (MMS).