Welcome to the ScienceDuo blog by Chris Wallis and Rhiannon Morris. Screeds on science and sanity from two people who understand neither.

Science snippets: RNAi, it’s RISCy business!

So I have decided to start some shorter blog posts about little Molecular biology things I enjoy. They’ll be super short, but hopefully interesting. Calling them science snippets or SNPs 😉

First up- RNA interference!

RNA interference or RNAi is a process whereby RNA inhibits the expression of genes. There are many uses for this process therapeutically and experimentally, but how does it work?

RNAi occurs because RNA molecules that are homologous to gene transcripts are produced, and the 2 RNA molecules hybridize forming dsRNA. This activates the RNA-induced silencing complex (RISC).
For example: transcription of a gene containing an inverted sequence can lead to gene silencing via this mechanism.

First DROSHA (an enzyme) removes non-hybridised regions of RNA in the nucleus. The pre-miRNA then enters the cytoplasm where dicer (another enzyme) can remove the hairpin loop in the RNA strands (in the case of an inverted gene) and cleave the RNA into smaller strands of around 20-25 bases long. Alternatively short interfering RNAs (siRNAs) can also be cleaved by dicer to produce small RNA strands. These short RNA molecules are then separated to form single stranded RNA (ssRNA), which act as a template with argonaute (a protein) that forms RISC. RISC will degrade and silence genes that are homologous to the RNA it strongly associates with by cleavage, or prevent the transcription of genes that are similar to the RNA by preventing translation.

Examples of the uses of RNAi include:

  1. In research for gene knockdown
  2. In medicine to turn off viral and cancer genes
  3. In GMO plants to remove certain traits


RNAi image

Blog post by Rhee


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This entry was posted on March 17, 2016 by in Uncategorized.
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