Digests double-stranded RNA. Involved in the processing of primary rRNA transcript to yield the immediate precursors to the large and small rRNAs (23S and 16S). Processes some mRNAs, and tRNAs when they are encoded in the rRNA operon. Processes pre-crRNA and tracrRNA of type II CRISPR loci if present in the organism (By similarity). Endonucleolytic cleavage to 5'-phosphomonoester. Homodimer. Belongs to the ribonuclease III family.