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In this article we will discuss about the concept of RNA interference technology.
RNA (RNAi) interference is an exciting field in biotechnology. This is a new approach for achieving shut down of target gene. In RNA interference method only a few double-stranded RNA (dsRNA) molecule will be employed per cell to silence the expression of target gene.
Therefore, it is invaluable research tool for down regulation of gene expression particularly in mammalian cells. It is several thousand times powerful than antisense technology.
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RNA interference was first discovered in worms in 1998. RNA interference operates in plants and other organisms like fungi and mammals. It is also a powerful regulatory process in viral defence and for transposon silencing in plans and animals. Presently, this technique is widely used for medical purpose in silencing of disease related genes.
Intense study on molecular mechanism of RNAi showed that dsRNA molecules are triggered in the partial study of gene silencing. Like antisense oligonucleotides, SiRNA or RNAi can be produced by chemical synthesis and delivered exogenously to cells or SiRNA can be induced by transfection of plasmids that express SiRNA endogenously under the control of RNA pol III promoters.
When double-stranded RNA is enter/available in cells, it is recognised and cut into pieces (21-23 bp) by an enzyme called Dicer. It is a member of RNase III family in ATP dependent progressive manner.
These 21-23 bp long with short overhangs is known as short interference RNA or SiRNA. In the next step of duplex SiRNA are the unwind by a helicase activity assemble with special proteins to form what is known as RNA induced silencing complex (RISC).
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This is otherwise called as sequence-specific mRNA eating machine. Unwinding of SiRNA takes place using ATP and one of the strands recognise complementary mRNA of target gene in the cell. Consequently double-stranded RNA is formed. This dsRNA from mRNA then becomes a substrate for Dicer cleavage activity, which results in the destruction of mRNA and formation of new SiRNA.
