Ambion™ Escherichia coli ribonuclease III (RNase III; EC 3.1.24) is a double-stranded RNA (dsRNA) specific endoribonuclease. In E. coli, RNase III cleaves ribosomal RNA (rRNA) precursors during maturation of rRNA. The enzyme cleaves dsRNA into 12–15 bp dsRNA fragments with 2 to 3 nucleotide 3' overhangs, and 5' phosphate and 3' hydroxyl termini. The termini and overhangs of RNase III cleavage products are thus the same as those produced by Dicer in the eukaryotic RNAi pathway. Transfection of RNase III cleavage products can be used to induce RNAi in mammalian cells (patent pending).

Unit Definition:
One unit is defined as the amount of enzyme catalyzing the cleavage of 1 μg of 500 bp dsRNA substrate to approximately 12–30 bp fragments in 60 min at 37°C.