RNA Interference an Important Technology
Authors: Komal Rachandra Pawar1*, Swapnil Gorakh Waghmare2
1VDCOAB, Vasantrao Naik Marathwada Agricultural University, Parbhani-431402
2CPBMB, Kerala Agricultural Univrity, Thrissur-680656

RNA interference is a recent but potent technology and is rapidly gaining wide acceptance. The initial discovery of this phenomenon was in 1991, by scientists trying to deepen the color of petunias. Surprisingly, by introducing a gene for color, they found that they had turned off the gene. RNA interference is abbreviated as RNAi. It is also known by other names such as post transnational gene silencing, transgene silencing and quelling. RNAi has been observed in all eukaryotes. RNA interference is a process of gene silencing mediated by short RNA molecules produced from double stranded RNA (dsRNA). Short RNAs are produced by cleavage of dsRNA by the nuclease called "dicer". Dicer is a nearly 200 kDa multidomain, an RNase 3 family enzyme which functions in producing short dsRNA called siRNA duplexes.

The siRNA molecules bind to a protein complex called RNA-induced silencing complex (RISC) which possess a helicase activity that unwinds the two strands of RNA molecules. The generated antisence RNA strands pair with the target RNA molecules. The active components of a RISC are endonucleases called argonaute protein then hydrolyses the target RNA at the site where the antisense strand is found. siRNA molecules can be synthesized chemically in vitro or in vivo by transcription. It may be pointed out that chemically synthesized siRNA molecules inhibit target gene expression for only 4-6 days. But the DNA vector construct once transfected into the cells will keep on generating siRNA molecules to cause a permanent inhibition of the gene.

miRNA is small, non-coding RNA molecules encoded in the genomes of plants, animals and their viruses. This RNA seems to regulate gene expression post transcriptionally by binding to the 3'-untranslated region (3'-UTR) of specific miRNA.

siRNAs derive from long, fully complementary double-stranded RNAs (dsRNAs) whereas miRNAs appeared to be processed from stem-loop precursors with incomplete double-stranded character. Both siRNA and miRNA has different origins. siRNAs originated exogenously while miRNAs endogenously. siRNAs base-pair perfectly and induce mRNA cleavage only in a single, specific target. miRNA typically have an incomplete base pairing to a target and inhibit the translation of many different mRNAs with similar sequence.

Though the RNA interference is effective gene silencing technology, it has some limitations such as1) this technology is based on exogenous siRNAs is rather short-lived (only 4-6 days) 2) delivery of exogenous siRNAs into cells is not highly efficient.

Functions of RNAi

RNA interference has an important function in the cell. Biologically RNAi is used by cells for the up-regulation and down-regulation of genes, but the mechanism behind is not known. Immunity is also driven by the RNA interference. Mainly viral infections are controlled by using the RNAi mechanism.

Applications of RNAi

RNAi has an important application in the process of gene knockdown. RNAi has been used in the study of functional genomics. RNAi used for treating cancer by specific gene silencing in tumor cells. RNAi has been used for development of novel crops by using biotechnology. It is also used for the lowering natural toxins in genetically engineered plants. RNAi can be developed for the production of specific insecticides. RNAi has been used for the improvement of stress tolerance and nutritional quality of crops. RNAi technology can be used to target the HIV-1 infections.

About Author / Additional Info:
Research scholar in VDCOAB, Vasantrao Naik Marathwada Agricultural University.