Fig. 4. Pulse–chase analysis of COS-7 cells coexpressing M-PMV and various BUL1 mutants. At 48 h after transfection of each BUL1 mutant DNA with pSHRM15 into COS-7 cells, cells were pulse-labelled and then chased for 2 or 6 h. Extracellular virions were pelleted from the culture fluids of chased cells. M-PMV-specific cell-associated (A) or virion-associated (B) proteins were immunoprecipitated with anti-M-PMV antiserum. The positions of M-PMV proteins are indicated on the right. (C) Expression of BUL1 mutants was also examined by immunoprecipitation with anti-c-Myc antiserum. Asterisks on the left indicate the migration positions of the wild-type or BUL1 mutants.