FIG. 4.

Bypass of p21 peptide-induced G₁ arrest. (A) Schematic of the p21 peptide. The p21 portion is boxed in white, and the internalization domain is boxed in black. The PCNA site is mutated (indicated by the gray A) such that only the cyclin/CDK-inhibitory site (labeled cyclin 2) is active. (B) Cell cycle profiles of HFKs treated with p21 peptide, with scrambled control peptide, or with water. pep., peptide. (C) Western blot showing Rb phosphorylation state in p21 peptide- or control-treated HFKs. cont., control peptide. (D) S-phase induction inp21 peptide-treated HFKs expressing E7 mutants. The S-phase fraction of peptide-treated HFKs expressing vector, E7 WT, or mutated E7 proteins was measured and graphed normalized to those of water-treated controls. Shown is a summary of the results of three experiments (raw data are presented in Table 2). Error bars represent standard deviations.