Figure 4.

Differential phosphorylation of Ku70 during cell cycle. HeLa cells were collected at the indicated time intervals after release from the arrest induced by double thymidine treatment. The presence of Ku70 in the anti-phospho-threonine-proline immunoprecipitates from the cell extracts and the supernatants were determined by anti-Ku70 immunoblotting (IB). The mean fold-change (±S.D.) of the intensities of the phospho-Ku70 (P-Ku70) bands in the immunoblots (n = 3) in different time points with respect to that at 0 h point were represented as column plot. Synchronization of the cells was checked by anti-cyclin E and anti-cyclin B immunoblotting and flow cytometer analysis after propidium iodide staining. Equal loading of protein samples were ascertained by anti-actin immunoblotting of the supernatants. AS, asynchronous culture of cells.