Effect of double-stranded RNAs from sindbis virus-infected cells on rabbit reticulocyte and chick embryo cell-free protein synthesis

1. Cell-free polypeptide synthesis in rabbit reticulocyte lysates was inhibited by extracts of Sindbis virus-infected cells and double-stranded RNAs which accumulate in Sindbis-infected cells. 2. All species of double-stranded RNA isolated from Sindbis-infected cells were found to have the same inhibitory ability, and caused significant inhibition at concentrations as low as 1 · 10^-10-1 · 10^-11 g/ml. 3. Cell-free polypeptide synthesis in chick embryo lysates was insensitive to Sindbis-infected cell extracts, double-stranded RNA isolated from Sindbis-infected cells, and a synthetic double-stranded polymer, poly(rI)-poly(rC), at all concentrations tested. The chick embryo cell-free extracts appeared to initiate polypeptide synthesis in vitro, since incorporation of ³H-labeled amino acids into acid-precipitable polypeptides by these extracts was inhibited by aurintricarboxylic acid (8 · 10^-5 M) and pactamycin (5 · 10^-7 and 10^-6 M). 4. Poly(U)-directed reticulocyte and chick embryo lysates at high Mg²⁺ concentrations were insensitive to inhibition by double-stranded RNA at all concentrations tested.