Question

Describe what RNAi with siRNA is, what miRNA is, and briefly describe what the slicer and dicer mechanism of inhibition is.

Answer 1

RNA interference (RNAi) is an important process, used to regulate the activity of genes (gene silencing). It can work by introducing two main players: small interfering RNAs (siRNAs) and microRNAs (miRNAs).

Small interfering RNA (siRNA), short interfering RNA, is a class of double-stranded RNA molecules, 20-25 base pairs in length, similar to miRNA, and operating within the RNA interference (RNAi) pathway. They can inhibit the expression of one specific target mRNA.

miRNAs (microRNAs) are short non-coding RNAs that is responsible to regulate gene expression post-transcriptionally. They normally can bind to the 3'-UTR (untranslated region) of their target mRNAs and repress protein production by destabilizing the mRNA and translational silencing. They are responsible to regulate the expression of multiple mRNAs.

The enzyme dicer is responsible to trim the double stranded RNA, to form small interfering RNA or microRNA. These processed RNAs are incorporated into the RNA-induced silencing complex (RISC), which targets messenger RNA to prevent translation.

The Argonaute protein family can plays a crucial role in RNA silencing processes, and that can play as an important component of the RNA-induced silencing complex (RISC). Argonaute proteins can bind to the different classes of small non-coding RNAs, such as miRNAs, siRNAs and Piwi-interacting RNAs (piRNAs). Small RNAs guide Argonaute proteins to their specific targets through the sequence complementarity (base pairing), which then leads to mRNA cleavage or translation inhibition.