Changes in CDK activities during erythroleukemia cell terminal differentiation.

Logarithmically growing MEL cells were induced to differentiate with 5 mmol/L HMBA as described in “Materials and methods.” (A) At the indicated times the cell number (○) and the percentage of benzidine-positive hemoglobinized cells (percent of B+, □) were determined. (B) Total cellular protein extracts were prepared and analyzed for specific CDK activities by immunoprecipitation (IP)-kinase assays, and (C) CDK protein levels were determined by immunoblotting as described in “Materials and methods.” BP indicates blocking peptide.