FIG. 4.

PAP contains a functional CRM. Inhibition of cdk phosphorylation of pRB by an 8-mer PAP-derived peptide. (A) Purified pRB and cyclin A-cdk2 were incubated under kinase conditions in the presence of [γ-³²P]ATP and two concentrations (9 and 18 μM) of either an 8-mer PAP CRM-derived peptide (SKIRILVG) (lanes 2 and 3), an 8-mer peptide of scrambled sequence (LRSGIKVI) (lanes 4 and 5), or no peptide (lane 1). Phosphorylated proteins were resolved by SDS-PAGE and detected by autoradiography. Arrows on the left indicate the positions of pRB and cyclin A. (B) Purified pRB and cyclin B₁-cdc2 were incubated under kinase conditions in the presence of [γ-³²P]ATP and the 8-mer PAP CRM-derived peptide (18 μM) (lane 2), the 8-mer peptide of scrambled sequence (18 μM) (lane 3), or no peptide (lane 1). Arrows on the left indicate the positions of pRB and cyclin B₁.