Figure 7.

CLT abrogates cdk2 activity. (A) Extracts prepared from the experiment depicted in Fig. 5A were immunoprecipitated with anticyclin E antibodies, and the activity of associated kinase was determined by using Histone H1 as substrate. (B) Activity of cyclin E-cdk2 complex after CLT addition was determined in bFGF-stimulated cells exposed to CLT (10 μM) for 1, 3, and 6 hr (CLT was added 8, 11, or 13 hr after bFGF). Cells were harvested 14 hr after initial bFGF stimulation; 25 μg of protein was immunoprecipitated with anticyclin E antibodies, and kinase activity was determined by using glutathione S-transferase-Rb as substrate.