Effect of cycloheximide on RNA metabolism early in productive infection with adenovirus 2

The presence of cycloheximide during the early phase of adenovirus 2 replication causes an increase in the virus-specific content of newly synthesized mRNA. The total cytoplasmic RNA from control cultures labeled 2 to 5 h after infection hybridized to viral DNA 0.8%, whereas RNA synthesized in the presence of cycloheximide annealed 6%. Cytosine arabinoside, an inhibitor of DNA synthesis, did not affect the percent hybridization to viral DNA. Oligo(dT)-cellulose chromatography was used to purify the portion of cytoplasmic RNA containing poly(A). The poly(A)-containing RNA from cultures labeled in the presence of cycloheximide hybridized to viral DNA 32% as compared to 2.2% for RNA from control cultures. Hybridization-inhibition experiments between RNAs from control- and cycloheximide-treated cultures demonstrated that the cultures treated with cycloheximide did not have an increased content of viral RNA or a new class of viral RNA sequences. Therefore, the increased hybridization appears to be caused by a reduction in synthesis of cellular cytoplasmic mRNA. Nucleoplasmic RNAs lacking and containing poly(A) were annealed to viral DNA. For both classes, RNA from cultures treated with cycloheximide hybridized 5- to 10-fold more than RNA from control-infected cultures. Therefore, the increased hybridization of cytoplasmic RNA synthesized in the presence of cycloheximide is caused either by reduced transcription of the cellular genome or by greatly increased instability of cellular heterogeneous nuclear RNA.