**2.1 Tyrosine phosphorylation of Rad51 by the c-Abl family of tyrosine kinases**

Several studies have shown that Rad51 can be phosphorylated on tyrosine but until recently there were discrepancies on the exact site of phosphorylation. Three studies had shown the phosphorylation of Tyrosine 315 (Y315) and only one the phosphorylation of Tyrosine 54 (Y54). A recent publication demonstrated that both of these tyrosines can be phosphorylated. The kinases which phosphorylate Rad51 belong to the c-Abl family which has two members, c-Abl and Arg. The oncogenic fusion tyrosine kinase BCR/Abl has also been shown to phosphorylate Rad51. However, other tyrosine kinases can also phosphorylate Rad51 at a different site than Tyrosine 315 in MEF cAbl-/- cells (Chen et al., 1999b).
