Other approaches to RNAi include DNA-directed RNAi (ddRNAi) that is used to produce dsRNA inside the cell, which is cleaved into siRNA by the action of Dicer, a specific type of RNAse III
. MicroRNAs are derived by processing of short hairpins that can inhibit the mRNAs.
The pri-miRNA is cleaved in the nucleus by RNAse III
(Drosha enzyme) and its cofactor, DiGeorge syndrome critical region gene 8 (DGCR8), resulting in one or more microRNA precursors called pre-miRNAs.
In the cytoplasm, pre-miRNA is processed by Dicer protein (endonuclease cytoplasmic RNase III
enzyme), and mature miRNA is produced.
Dicer1 is an RNase III
endoribonuclease which has several functions but crucially is involved in the microRNA (miRNA) biogenesis pathway.
These transcribed miRNA molecules are processed by a well-organized processing mechanism, referred to as the "miRNA machinery" , which is controlled by various components such as RNase III
endonuclease Drosha (RNASEN), a double-strand RNA binding protein called the DiGeorge syndrome critical region gene 8 (DGCR8), the RNase III
ribonuclease Dicer, and a component of the RNA-induced silencing complex (RISC) called Argonaute 2 (AGO2).
It is subsequently cleaved near the hairpin stem base, by RNase III
Drosha and protein partner, Di George syndrome critical region 8.
Further this pri-miRNA is cut by RNase III
, DROSHA and its co-factor DGCR8 into smaller ~ 70 nucleotide stem loops called as pre-RNA.2,3 The pre-RNA moves from the nucleus to the cytoplasm by means of exportin-5.
The mechanism of RNase III
action: how dicer dices.
Dicer belongs to family of ribonuclease type III (RNase III
) enzyme that plays an important role in the biosynthesis of miRNA by cleaving the pre-miRNA into mature double-stranded miRNA (ds-miRNA) of ~21 nucleotide length.
The generally accepted view of miRNA biogenesis is that primary miRNA transcripts are cleaved to stem-loop intermediates, known as pre-miRNAs, in the nucleus by the RNase III
Many papers center around RNA, including nonsense-mediated mRNA decay, bacterial metabolic regulation, editing in plants, RNase III
, transcriptional elongation control, and adaptive translation.