Effect of RNAase III, cleavage on translation of bacteriophage T7 messenger RNAs.

Abstract

Most bacteriophage T7 messenger RNAs are cut at specific sites by a host enzyme, RNAase III. Such cleavages do not occur in RNAase III-deficient host strains, but T7 is able to grow in such strains, and all but a few T7 proteins are made at essentially the same rate in RNAase III− as in RNAase III+ strains. The exceptions are the gene 0·3 protein, an early protein, and a few late proteins. Cleavage of the early messenger RNAs by RNAase III greatly stimulates the production of the 0·3 protein, both in vivo and in cell-free protein synthesizing systems, but has relatively little effect on synthesis of the other four early proteins. The in vitro experiments demonstrate that the products of RNAase III cleavage are active messenger RNAs and not inactive intermediates in a degradation process.