Western blot assays of BZLF1 and PCNA at the indicated times after induction with anti-Ig in AK31 cells containing Zp-82LF1 plasmids. The upper panels are wild-type Zp, and the lower panels are the MV mutant form of Zp. Protein samples were electrophoresed on 12.5% SDS gels, blotted to nitrocellulose, and probed with either BZ-1 (1:500 dilution) or PCNA antibody PC10 (1:1,000), followed by enhanced-chemiluminescence detection (Amersham).