Levels of cyclins and CDK inhibitors and their associations with CDKs during MEL cell differentiation.

Total cellular protein extracts were prepared at the indicated times of HMBA treatment, and the levels of (A) specific cyclins and (C) CDK inhibitors were determined by immunoblotting. Extracts were immunoprecipitated (IP) with antibodies specific for the indicated (B) cyclin or (D) CDK inhibitor as described in “Materials and methods.” The immunoprecipitates were subjected to sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotted for the indicated CDK.