Encephalomyocarditis virus RNA: variations in polyadenylic acid content and biological activity

Abstract

Encephalomyocarditis (EMC) viral RNA was isolated from purified virus grown in Ehrlich ascites tumor cells. The viral RNA contained polyadenylic acid [poly(A)] regions that were very heterogeneous in length. Chromatography of the EMC viral RNA on oligo(dT)-cellulose columns separated the RNA into 3 distinct fractions (peaks 1-3). Approximately 20% of the EMC viral RNA appeared as peak 1, 40% as peak 2 and 40% as peak 3. The RNA in each fraction appeared to be intact as shown by co-sedimentation with 35S unfractionated EMC viral RNA in SDS[sodium dodecyl sulfate]-sucrose density gradients. Approximately 95-100% of peaks 1 and 3, and 60-70% of peak 2, reappeared at the same elution position after rechromatography on oligo(dT)-cellulose. The RNA in peak 1 contained poly(A) with an average length of 16 nucleotides, peak 2 contained poly(A) with an average length of 26 nucleotides and peak 3 contained an average of 74 nucleotides in its poly(A) region. The distribution in the 3 fractions and the average length of the poly(A) moieties was relatively unaffected by changes in the cell suspension medium used during infection. Each of the 3 viral RNA fractions were assayed for biological activity using an infectious RNA assay on [mouse] L-cell monolayers. Infectivity of the viral RNA increased with poly(A) length, with peak 3 viral RNA being approximately 10 times more infectious than peak 1 viral RNA.