v-cyclin associates with p27^KIP1 in PEL cells. (A) Total lysates of PEL cells (40 μg) were resolved by SDS-PAGE (12%) and immunoblotted with antibodies to v-cyclin, p27^KIP1, CDK6, CDK4, and CDK2. BC-1, BC-2, BC-3, and BCBL-1 are KSHV-positive PEL cell lines, and JOK-1 cells are KSHV-negative leukemia cells. (B) Lysates of the PEL and JOK-1 cells were immunoprecipitated (IP) with anti-v-cyclin (2 top panels) or anti-p27^KIP1 antibodies (2 bottom panels) and analyzed for associated proteins on SDS-PAGE by immunoblotting with anti-v-cyclin and anti-p27^KIP1 antibodies. The interaction between v-cyclin and p27^KIP1 after immunoprecipitation with anti-p27^KIP1 antibodies is readily detectable in a short exposure from BC-3 cells (left), whereas a longer exposure was used for BC-1, BC-2, and BCBL-1 (right).