ADARentsyymien

ADARentsyymit are a class of enzymes that play a crucial role in RNA editing. Specifically, they catalyze the conversion of adenosine (A) to inosine (I) within RNA molecules. This process, known as A-to-I editing, is a significant post-transcriptional modification that can alter the coding potential of messenger RNAs (mRNAs) and affect the structure and function of non-coding RNAs. In mammals, ADARs are encoded by a family of three genes: ADAR1, ADAR2, and ADAR3. ADAR1 and ADAR2 are catalytically active, while ADAR3 is believed to be catalytically inactive.

The A-to-I editing mediated by ADARs is highly specific and occurs at precise adenosine residues within double-stranded RNA (dsRNA) structures. These dsRNA structures can arise from complementary base pairing within a single RNA molecule (intramolecularly) or from the annealing of two separate RNA molecules (intermolecularly). ADAR enzymes recognize these dsRNA structures and facilitate the deamination of the adenosine base. The resulting inosine is then read as guanosine (G) by the ribosome during translation, leading to a change in the amino acid sequence of the encoded protein.

A-to-I editing has profound implications for cellular function. It can create or abolish splice sites, alter codons, and generate microRNAs with different target specificities. This flexibility allows for the diversification of the transcriptome and proteome without the need for changes in the genome itself. Dysregulation of ADAR activity has been linked to a variety of diseases, including neurological disorders and cancer, highlighting the essential role of these enzymes in maintaining cellular homeostasis.