Transport of viral RNA in kb cells infected with adenovirus type 2.
Messenger RNA transport was studied in KB cells infected with the nuclear DNA virus adenovirus type 2. Addition of 0.04 microg/ml of actinomycin completes the inhibition of ribosome synthesis normally observed late after infection and apparently does not alter the pattern of viral RNA synthesis: Hybridization-inhibition experiments indicate that similar viral RNA sequences are transcribed in cells treated or untreated with actinomycin. The polysomal RNA synthesized during a 2 hr labeling period in the presence of actinomycin is at least 60% viral specific. Viral messenger RNA transport can occur in the absence of ribosome synthesis. When uridine-(3)H is added to a late-infected culture pretreated with actinomycin, viral RNA appears in the cytoplasm at 10 min, but the polysomes do not receive viral RNA-(3)H until 30 min have elapsed. Only 25% of the cytoplasmic viral RNA is in polyribosomes even when infected cells have been labeled for 150 min. The nonpolysomal viral RNA in cytoplasmic extracts sediments as a broad distribution from 10S to 80S and does not include a peak cosedimenting with 45S ribosome subunits. The newly formed messenger RNA that is ribosome associated is not equally distributed among the ribosomes; by comparison to polyribosomes, 74S ribosomes are deficient at least fivefold in receipt of new messenger RNA molecules.
Institute for Molecular Virology and the Department of Pathology, Saint Louis University School of Medicine, Saint Louis, Missouri 63104.
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Okubo