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Abstract
RNA molecules labelled in BHK 21 cells following infection with vesicular stomatitis virus in the presence of Actinomycin D and 32PO4 were examined. A complex pattern was obtained when the RNA was centrifuged in sucrose gradients, at least five radioactive peaks being found. These had sedimentation coefficients in sucrose gradients in 0.1 M-sodium acetate, pH 5.0, of approx, 38 S, 28 S, 20 S, 12 S and less than 4 S. Two, 2, 12, 16 and 8% respectively of the radioactive RNA was resistant to ribonuclease 1 μg./ml. Treatment of the unfractionated induced RNA with ribonuclease 1 μg./ml. yielded a product which had a heterogeneous sedimentation profile (7 to 11 S) in sucrose gradients. Recentrifuging individual fractions of this peak in separate gradients confirmed that the ribonuclease-resistant RNA was heterogeneous. The ribonuclease-resistant RNA also gave a heterogeneous profile in caesium sulphate gradients, with a density range of 1.61 to 1.65 g./ml. The induced RNA which sedimented most slowly in the sucrose gradients could be separated from the labelled cellular 4 S RNA by filtration through Sephadex G-75. The base composition of this RNA was significantly different from those of the faster sedimenting induced RNA molecules. Its association with vesicular stomatitis virus infection was confirmed by the failure to detect a similar slowly sedimenting RNA in uninfected cells or in cells infected with foot-and-mouth disease virus.
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