Synthesis of a structural adenovirus polypeptide in the absence of viral DNA replication

HeLa cells were pulse labeled with [³⁵S]methionine at different times after infection with adenovirus type 2 to follow the kinetics of viral polypeptide synthesis. Cell lysates were prepared and viral proteins were analyzed by immunoprecipitation with antisera directed against "early" polypeptides or selected structural proteins of the adenovirus particle. The results showed that polypeptide IX, a structural component of the virion, is synthesized earlier than other structural polypeptides. Polypeptide IX is further distinguished from other components of the virion in that it is synthesized in the presence of cytosine arabinoside, a drug which blocks viral DNA replication. Cycloheximide, another drug which blocks viral replication and the onset of "late" viral transcription, also fails to prevent the accumulation of the messenger RNA coding for polypeptide IX, although mRNAs corresponding to the other structural viral components remain undetectable. Size fractionation of infected cell RNA showed that, like its "late" counterpart, the "early" messenger RNA for polypeptide IX sediments at 9 S. These results indicate that the regulation of the gene for polypeptide IX differs from that of other genes for structural adenovirus polypeptides.