Figure 4.

Cell-cycle regulatory protein expression, CDK kinase activities, and complex formation in K5CDK4D158N epidermis. A: Epidermal lysates from Wt and K5CDK4^D158N (Tg) mice were probed with antibodies for CDK4, CDK2, cyclin D1, cyclin E, p27^Kip1, p21^Cip1, and actin as loading control. B: CDK2 and CDK4 in vitro kinase assays using pRb peptide as substrates. Epidermal lysates from K5CDK4^D158N (Tg) and Wt littermates were immunoprecipitated with antibodies against CDK4, CDK2, or normal rabbit IgG (lane 3) and incubated with pRb peptides. C: Fresh epidermal lysates from K5CDK4^D158N Tg mice and Wt littermates were immunoprecipitated with polyclonal antibodies against cyclin D1(IP Cyc D1), p27^Kip1 (IP p27), and p21^Cip1 (IP p21) and immunoblotted with polyclonal antibody for CDK4 (IB-CDK4), cyclin D1 (IB-Cyc D1), and p27^Kip1 (IB-p27).