A Role for Ribonuclease III in Processing of Ribosomal Ribonucleic Acid and Messenger Ribonucleic Acid Precursors in Escherichia coli

AB105, a strain deficient in RNase III, produces a 30 S precursor to ribosomal RNA (mol wt, 2.1 x 106) that is then metabolized to 25 and 17.5 S rRNA; after infection of the strain with T7 phage, a precursor of T7 messenger RNA of molecular weight 3.5 x 106 is formed and then metabolized to smaller mRNA chains. Purified RNase III cleaves the extracted large RNAs to products with the electrophoretic mobilities of the cleavage products produced in vivo.