Interference RNA

Dear friends,

This time I would like to discuss with you some aspects about the interference RNAa synthetic one, which found to have wide therapeutic application in cancer, influenza, hypercholesterol etc. This is a newly described technique which provide a quick and relatively easy way to analyze the function of any gene whose sequence is known.In 2006, Andrew Fire and Craig C. Mello shared the Nobel Prize in Physiology or Medicine for their work on RNA interference in the nematode worm.

RNA interference (RNAi) is a mechanism that inhibits gene expression at the stage of translation or by hindering the transcription of specific genes. RNAi targets include RNA from viruses and transposons (significant for some forms of innate immune response), and also plays a role in regulating development and genome maintenance. Small interfering RNA strands (siRNA) are key to the RNAi process, and have complementary nucleotide sequences to the targeted RNA strand. Specific RNAi pathway proteins are guided by the siRNA to the targeted messenger RNA (mRNA), where they "cleave" the target, breaking it down into smaller portions that can no longer be translated into protein. A type of RNA transcribed from the genome itself, microRNA (miRNA), works in the same way.

The basic idea of RNAi is that a double stranded RNA complementary to a segment of the mRNA is synthesized, introduced into the cell, and a cell system then degrades and destroys the mRNA complementary to the double stranded RNA. Any newly synthesized copies of thatmRNA will be degraded soon after they are made. Sincethe mRNA has been destroyed and there is none of that specific mRNA available to be translated , there is none of that specific mRNA available to be translated , there is no mRNA to serve as a template for synthesizing that protein. Once the preexisting protein that was made from that mRNA before its destruction is degraded by the cell, the protein will be degraded over time and disappear from the cell. This process is sometimes reffered as gene silencing

The RNAi pathway is initiated by the enzyme dicer, which cleaves long, dsRNA molecules into short fragments of 20–25 base pairs. One of the two strands of each fragment, known as the guide strand, is then incorporated into the RNA-induced silencing complex (RISC) and pairs with complementary sequences. The most well-studied outcome of this recognition event is post-transcriptional gene silencing about which I explained earlier. This occurs when the guide strand specifically pairs with an mRNA molecule and induces the degradation by argonaute, the catalytic component of the RISC complex. Another outcome is epigenetic changes to a gene – histone modification and DNA methylation – affecting the degree the gene is transcribed.