RNA interference (RNAi): by Nature Video


scientists have been making rapid progress in understanding RNA interference or RNAi AI many organisms use RNAi eye to control genes and it can also be used as a tool in the laboratory and in the future perhaps as a therapy this animation will introduce you to the principles of RNAi I involving two important types of RNA molecule small interfering RNAs and micro RNAs eukaryotic cells have many sophisticated ways of controlling gene expression in the complex environment of a cell these mechanisms need to be precisely targeted there’s a group of mechanisms that use small RNA molecules to direct gene silencing this is called RNAi I inside the nucleus most genes that encode proteins are transcribed by RNA polymerase 2 the primary RNA transcript is processed by splicing and forms a mature messenger RNA sometimes called mRNA the messenger RNA is then exported from the nucleus into the cytoplasm here ribosomes catalyze translation of the messenger RNA to form polypeptide chains that fold into proteins but this is also where some small RNA molecules can have their silencing effects there are several types of regulatory small RNA small interfering RNAs known as SI rnas are derived from longer double-stranded RNAs that are either produced in the cell itself or are delivered into cells experimentally the introduction of si RNAs or double stranded RNA is widely used to manipulate gene expression micro RNAs are another type of small RNA most micro RNAs come from RNAs that are transcribed in the nucleus which then fold and a processed before being exported into the cytoplasm as double stranded precursor micro RNAs the double-stranded precursors of micro rnas and si RNAs bind to Dicer which is an endonuclease protein that cuts the RNA into short segments most si RNAs and micro rnas are approximately 21 nucleotides long the short double-stranded RNA then binds an Argonaut protein one strand of the RNA is selected and remained bound to Argonaut this is called the guide strand the combination of the RNA and Argonaut along with other proteins is called the RNA induced silencing complex or risk Si RNAs direct risk to bind to specific messenger RNAs the targeting is precise because it’s determined by base pairing between the si RNA and the target messenger RNA si RNAs often have perfect complementarity to their target sites once bound Argonaut catalyzes cleavage of the messenger RNA which will then be degraded microRNAs also guide risk to messenger RNAs usually only part of a micro RNA known as the seed pairs with a target messenger RNA this imprecise matching allows micro rna’s to target hundreds of endogenous messenger rnas targeting bio micro RNA can lead to messenger RNAs being degraded or translation being inhibited argonauts and their small regulatory RNA cofactors are found in plants animals fungi and some bacteria and their importance in a multitude of biological processes and as tools continues to be revealed you

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