Interferon action: two distinct pathways for inhibition of protein synthesis by double-stranded RNA.

Double-stranded RNA inhibits protein synthesis in at least two ways. It activates a protein kinase that blocks peptide chain initiation by phosphorylating the peptide chain initiation factor eIF-2 and also activates an endonuclease that inactivates different mRNAs at different rates. The protein kinase and the endonuclease have been partially purified from interferon-treated Ehrlich ascites tumor cells. The 2',5'-oligoadenylates pppA(2'p5'A)n, found found earlier to be mediators in the activation of the endonuclease by double-stranded RNA, are not mediators in the activation of the protein kinase by double-stranded RNA.