FIG. 6.

K-bZIP is phosphorylated by CDK in vitro. Extracts from BJAB cells, uninduced BCBL-1 cells, and BCBL-1 cells that had been induced with TPA for 48 h were labeled by addition of CDK2F80G-cyclin E, CDK2F80G-cyclin A, or CDC2F80G-cyclin B and of N⁶-benzyl-[γ-³⁵S]ATP. The extracts were incubated at room temperature and immunoprecipitated with anti-K-bZIP sera (A) or anti-ORF 73 (B). The immunoprecipitate (IP) was analyzed on SDS-PAGE gels followed by electroblotting onto Immobilon and exposure to film. Arrows indicate the position of the K-bZIP protein (A) and the ORF 73 (LANA) protein (B).