Figure 5.

Chk1, 14-3-3σ, and p21 coprecipitates with p53 in wild-type cells following irradiation. Wild-type and 14-3-3σ knockout HCT 116 cells were irradiated to 10 Gy and extracts were immunoprecipitated with p53 antibody, FL393 (rabbit), followed with immunoblotting with mouse antibodies for Chk1 (G4), 14-3-3σ (N-14), p21 (WAF1), and Ku70 (N3H10). [Because p53 and Chk1 are of similar size and cannot be probed on the same blot, equivalent p53 precipitation was confirmed by Western analysis on a separate blot using p53 antibody, DO1 (mouse). The cross-reacting rabbit IgG band (from FL393) on this blot serves as an internal loading control. Analysis of whole-cell extracts showed Ku70 to be highly expressed in HCT116 cells.]