The respective roles of the protein kinase and pppA2′ p5′ A2′ p5′ a-activated endonuclease in the inhibition of protein synthesis by double stranded RNA in rabbit reticulocyte lysates

Double-stranded RNA (dsRNA) inhibits protein synthesis in rabbit reticulocyte lysates by activating the synthesis of the endonuclease effector pppA2′ p5′ A2′ p5′A (2-5A) and a protein kinase which phosphorylates the protein synthesis initiation factor eIF-2. Under certain assay conditions, high concentrations of dsRNA are without inhibitory effect in many lysates (high dsRNA "reversible" lysates). In these lysates natural dsRNA at low concentrations stimulated protein kinase activity to a greater extent than did the synthetic dsRNA poly rI.rC. Synthesis of 2-5A was greater when poly rI.rC was used. However, a number of factors, including the salt concentration and messenger RNA used, combine to determine the overall effect of dsRNA on protein synthesis under any given set of experimental conditions.