In mammals, the most common form of ribonucleic acid (RNA) editing, alteration of the sequence of nucleotides, is the conversion of adenosine to inosine. Common in the nervous system, this takes place by deamination where enzymes act as protein catalysts, removing amine groups from molecules. ADAR1 and ADAR2 are just such deaminases. In RNA interference, small RNA molecules (microRNAs or miRNAs, and small interfering RNAs or siRNAs) can bind to other specific RNAs (mRNA) and either increase or decrease their activity. RNA interference (RNAi) has an important role in defending cells as well as directing gene development and expression in general. The 'Understanding the mechanism behind ADAR1 (Adenosine DeAminase acting on RNA 1) modulation of the RNA interference pathway' (ADAR1 and RNAi) project aimed to determine if there is an overlapping of RNA editing and RNAi, and if the processes actually antagonise each other. Researchers performed deep sequencing of small RNAs to determine if after an increase in the editing enzyme's volume and activity there also would be an increase in the editing of miRNAs. The ADAR1 and RNAi study revealed that increased ADAR1 expression actually did not have an effect on miRNAs. The result suggests there is no overall change in miRNA activity following increased RNA editing However, researchers hypothesised that effects of an increase in ADAR1 expression could be more difficult to detect. To investigate, they proceeded with modification and mutation experiments to discover what was required for an interaction between miRNAs precursors and ADARs to take place. Results showed that the two pathways could antagonise each other but only on certain miRNAs. Also, the project found that this interaction could be independent of enzymatic activity.
Understanding the mechanism behind ADAR1 (Adenosine DeAminase acting on RNA 1) modulation of the RNA interference pathway
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31 May 2019