Figure 4.

ABHA treatment affects the expression and activity of cell cycle regulators. (A) Cells were treated with 100 μg/ml ABHA as indicated and harvested after 24 h, lysed, and immunoblotted for the indicated cell cycle regulatory proteins. The positions of the hyper- and hypophosphorylated forms of Rb and cdc2 are indicated by the arrowheads. (B) Cdk2 immunoprecipitate H1 kinase activity was assessed from cells treated as in A. No phosphorylation of H1 was detected in the ABHA-treated NFF sample even on longer exposures.