[MS2 RNA hydrolysis by snake venom phosphodiesterase and template properties of RNA produced by limited exonucleolytic action].

The action of snake venom phosphodiesterase on bacteriophage MS2 RNA under conditions of limited hydrolysis has been studied. The content of 5'-mononucleotides released during hydrolysis does not correspond to the calculated one based on the 3'-terminal nucleotide sequence of MS2 RNA. This finding suggests the occurrence of endonucleolytic splits in MS2 RNA with concomitant exonucleolytic digestion of some newly formed fragments. A high molecular weight RNA fraction, comprising unfragmented MS2 RNA with about 5-63'-terminal nucleotides removed is separated by sucrose gradient centrifugation and shown not to differ from the native MS2 RNA in its template function in a cell-free protein synthesizing system. It is demonstrated that template activity, polarity of translation, and nascent peptide chain termination on the MS2 replicase cistron are not affected by the removal of 3'terminal nucleotides of MS2 RNA. Consequently, these nucleotides are unessential in translation of native MS2 RNA.