Detection of c-Abl kinase-promoted phosphorylation of Rad51 by specific antibodies reveals that Y54 phosphorylation is dependent on that of Y315.

Rad51 plays a crucial role in homologous recombination and recombinational DNA repair. Its activity is regulated by phosphorylation by the c-Abl kinase. Either Tyr54 or Tyr315 have been reported as the target of phosphorylation but the interconnection between their phosphorylation is not known. We prepared two specific antibodies that selectively detected the Tyr54 or Tyr315 phosphorylation site of Rad51. By co-transfection of HeLa cells with c-Abl and Rad51, we clearly showed that both Tyr54 and Tyr315 of Rad51 are phosphorylated by c-Abl. Furthermore, we showed that the phosphorylation of Tyr315 stimulates that of Tyr54, which indicates that the phosphorylation of Rad51 by the c-Abl kinase is a sequential process.