Figure 4.

Absence of the ie1 protein pp89 in cells infected with ie1 mutant MM96.01. MEF were either mock-infected, infected with recombinant virus MC96.73 or ie1 mutant MM96.01 in the presence of cycloheximide (50 μg/ml) for 3 h to achieve the selective expression of ie genes (16). After removal of cycloheximide, actinomycin D (5 μg/ml) was added and proteins were labeled with [³⁵S]-methionine (1,200 Ci/mmol) for an additional 3 h. Lysis of cells and immunoprecipitations were performed as described (28) using an antiserum directed to the C terminus of the ie1 protein (a) and an ie1/ie3-specific antipeptide serum (b) directed against N-terminal sequences (16, 28). A long exposure of the autoradiograph in b is shown in c.