Ribonuclease 3 (Drosha)

Ribonuclease III double-stranded (ds) RNA-specific endoribonuclease that is involved in the initial step of microRNA (miRNA) biogenesis. Part of the microprocessor complex that is required to process primary miRNA transcripts (pri-miRNAs) to discharge precursor miRNA (pre-miRNA) from the nucleus.

Within the microprocessor complex, DROSHA cleaves the 3' and 5' strands of a stem-loop in pri-miRNAs (processing centre 11 bp from the dsRNA- ssRNA junction) to discharge hairpin-shaped pre-miRNAs that are subsequently cut by the cytoplasmic DICER to create mature miRNAs. Involved also in pre-rRNA processing.