Biochemical Basis of RNA Editing

Biochemical Basis of RNA Editing

RNA editing is a post-transcriptional process that alters the nucleotide sequence of RNA molecules. This process can lead to changes in the encoded protein sequence, ultimately affecting the function of the protein. RNA editing occurs in various organisms, including humans, and plays a critical role in regulating gene expression and protein function.

Mechanisms of RNA Editing

There are several mechanisms of RNA editing, with the most common being adenosine-to-inosine (A-to-I) editing and cytidine-to-uridine (C-to-U) editing. In A-to-I editing, the enzyme adenosine deaminase acts on adenosine bases in RNA molecules, converting them to inosine. In C-to-U editing, the enzyme cytidine deaminase catalyzes the conversion of cytidine bases to uridine. These editing events can occur in coding and non-coding regions of RNA molecules, leading to changes in the genetic code or affecting RNA stability and structure.

Enzymes Involved in RNA Editing

Several enzymes are involved in the process of RNA editing. For A-to-I editing, the adenosine deaminase acting on RNA (ADAR) family of enzymes catalyzes the conversion of adenosine to inosine. There are three ADAR proteins in humans, ADAR1, ADAR2, and ADAR3, each with different substrate specificities and functions. For C-to-U editing, the enzyme cytidine deaminase is responsible for catalyzing the conversion of cytidine to uridine. These enzymes play a crucial role in regulating RNA editing events and maintaining cellular homeostasis.

Biological Functions of RNA Editing

RNA editing has diverse biological functions, including regulating gene expression, generating protein diversity, and protecting cells from viral infections. In some cases, RNA editing can lead to the production of multiple protein isoforms from a single gene, increasing the functional diversity of the proteome. Additionally, RNA editing can alter miRNA binding sites, affecting post-transcriptional gene regulation. Furthermore, RNA editing can also protect cells from viral infections by editing viral RNA genomes, preventing their replication and spread within the host.