RNAmuokkauksessa

RNAmuokkauksessa, often translated as RNA editing, is a post-transcriptional modification process that alters the nucleotide sequence of an RNA molecule after it has been transcribed from DNA. This change can occur in various types of RNA, including messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). The most common types of RNA editing are adenosine-to-inosine (A-to-I) and cytidine-to-uridine (C-to-U) editing.

A-to-I editing is catalyzed by a family of enzymes called adenosine deaminases acting on RNA (ADARs). Inosine, the product of A-to-I editing, is recognized by the cellular machinery as guanosine during translation. This means that an A-to-I edit can lead to a codon change, resulting in a different amino acid being incorporated into a protein. This can significantly alter protein function, sometimes in profound ways. For example, A-to-I editing in the nervous system plays a critical role in regulating neurotransmitter receptor function and ion channel activity.

C-to-U editing is mediated by a different set of enzymes, primarily apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like (APOBEC) enzymes. This type of editing directly changes a cytosine nucleotide to a uridine. C-to-U editing is particularly well-known for its role in creating stop codons in certain mRNAs, thereby truncating the resulting protein.

RNA editing can affect gene expression at multiple levels, influencing protein sequence, RNA stability, splicing, and translation efficiency. It is a widespread phenomenon found in a diverse range of organisms, from viruses and invertebrates to mammals. The study of RNA editing is crucial for understanding cellular function, genetic diversity, and the origins of certain diseases.