RPA2 and Ataxia-telangiectasia: In addition, compared to the control cells, the delivery of IR to CCNF K/O cells induced increase of RPA32 phosphorylation at Ser4/Ser8 (a marker of ssDNA at DSB repair sites upon Ataxia telangiectasia mutated and DNA-PK activation), Ser33 (marker of ssDNA upon Ataxia telangiectasia related activation) and γH2Ax levels at steady-state level and after IR (Fig. 1E).