Fig. 3. Forskolin induces a transient inhibition of the cyclin-associated kinase activities. Reh cells were treated with forskolin (100 µM) for the times indicated. Total cell lysates (500 µg) were subjected to immunoprecipitation (IP) with the appropriate antibodies, and kinase assays were performed as described in Materials and Methods, using histone 1 or GST-RB as substrate. One representative experiment of three is shown. ns, nonspecific antibody used as a negative control.