FIG. 1.

Characterization of Cdc25A antibodies. (A) Extracts of HeLa cells (lanes 1 and 3) and HS68 cells (lane 2) were resolved by SDS-PAGE, transferred to nitrocellulose, and probed with affinity-purified Cdc25A antibodies raised against the full-length protein (lanes 1 and 2) or preimmune serum (lane 3). (B) Cdc25A was immunoprecipitated from HeLa cell extracts with a C-terminal peptide antibody in the absence (lane 1) or presence (lane 2) of antigenic peptide and incubated with tyrosine-phosphorylated inactive cyclin B-Cdk1 complex. Activation of cyclin B-Cdk1 caused by Cdc25A was monitored on histone H1 as substrate. Lane 3 shows a control immunoprecipitation using preimmune (PI) serum. IP, immunoprecipitant.