gene silencing effects of miRNAs as well as silencing triggered by foreign Dsrna.
When the Dsrna is exogenous(coming from infection by a virus with an RNA genome
A total number of 2,400
embryos were injected with a 2 µg/µl Dsrna mixture, from which 548 larvae hatched
and 216 adults survived(unpublished data).
RNA interference is a powerful tool for such studies and
it can be achieved through the microinjection of Dsrna(double-stranded RNA) or siRNA(small interfering RNA).
The phenomenon of RNA interference, broadly defined, includes the endogenously induced
gene silencing effects of miRNAs as well as silencing triggered by foreign Dsrna.
Exogenous Dsrna is detected and bound by an effector protein,
known as RDE-4 in C. elegans and R2D2 in Drosophila, that stimulates dicer activity.
The RNAi pathway is found in many eukaryotes, including animals, and is initiated by the enzyme Dicer,
which cleaves long double-stranded RNA(Dsrna) molecules into short double-stranded fragments
of ~21 nucleotide siRNAs.
When the Dsrna is exogenous(coming from infection by a virus with an RNA genome
or laboratory manipulations), the RNA is imported directly into the cytoplasm and cleaved to short fragments by Dicer.
The Dsrna portion of this pre-miRNA is bound
and cleaved by Dicer to produce the mature miRNA molecule that can be integrated into the RISC complex; thus, miRNA and siRNA share the same downstream cellular machinery.