REGULATORY REGION OF MS2-PHAGE RNA REPLICASE CISTRON .3. CHARACTERIZATION OF FRAGMENTS RESULTING FROM S1 NUCLEASE DIGESTION

The functionally active fragments MS2 R(-53←6) and MS2 R(-53←3) comprising the regulatory region for the replicase cistron have been isolated from MS2 RNA-coat protein complex following TI RNase digestion. In order to obtain shorter fragments, active in coat protein binding and initiation of translation, MS2 R(-53←6) was cleaved with S1 nuclease. The results indicate that Sl nuclease attacks the most susceptible loop regions of the two hairpin helices of MS2 R(-53←6). Amon the three fragments which have been isolated, only W 2 R(-35/33←6) containing the intact hairpin (b) region with initiation codon AUG is active in the coat protein binding. Functional activity exerted by another polynucleotide MS2 R(-17←6) supports the assumption that specific binding with the coat protein is determined by the hairpin (b) region prior to the replicase cistron. © 1979 Information Retrieval Limited.