The Lack of Messenger Activity of Ribonucleic Acid Complementary to the Viral Ribonucleic Acid of Bacteriophage R17

Abstract

Abstract RNA complementary to bacteriophage R17 RNA, isolated from bacteria infected with the virus, failed to stimulate protein synthesis in cell-free extracts of Escherichia coli. Under conditions optimal for protein synthesis under the direction of R17 viral RNA, the incorporation of amino acids into peptide linkage in the presence of complementary strand RNA was the same as the incorporation in the absence of added RNA, and the products formed were indistinguishable from the endogenous products. With several preparations of complementary strand RNA a small amount of amino acid incorporation was observed, but it correlated with the degree of contamination by viral RNA. Furthermore, peptide mapping of the material formed revealed that viral coat protein was the major product. The lack of messenger activity of the complementary strand can be explained by the fact that it failed to bind to ribosomes. Although incapable of associating with ribosomes and of initiating protein synthesis on its own, complementary strand RNA enhanced the incorporation of amino acids directed by viral RNA. This stimulatory effect of complementary strand RNA is not understood. We have shown, however, that the complementary strand RNA became partially resistant to RNase after incubation with the viral RNA in the E. coli extracts, and that it associated with ribosomes if the viral RNA was present. The effects of complementary strand RNA on the messenger activity of R17 viral RNA and the increased protection against RNase degradation suggest, but do not prove, that an association of the two strands takes place under the incubation conditions for cell-free protein synthesis.