MTase

MTase, short for methyltransferase, is an enzyme that transfers a methyl group from a donor, typically S-adenosyl-L-methionine (SAM), to a recipient molecule. Methylation can alter chemical properties, three-dimensional structure, and interactions, thereby regulating activity and function. MTases are found across all domains of life and are commonly categorized by their substrates: DNA, RNA, or proteins.

DNA methyltransferases catalyze the transfer of a methyl group to DNA bases, most often cytosine or adenine. In bacteria, DNA MTases are a component of restriction-modification systems that protect host DNA by methylation. In eukaryotes, DNA methylation modulates gene expression and other chromatin features. Common prokaryotic examples include Dam, which methylates adenine in GATC sequences, and Dcm, which methylates cytosine in CCWGG sites. In vertebrates and some other organisms, DNMT1, DNMT3A, and DNMT3B methylate cytosines in the CpG context, contributing to epigenetic regulation.

RNA methyltransferases modify ribosomal, transfer, and messenger RNAs, influencing RNA stability, processing, splicing, and translation. The METTL3-METTL14 complex is a well-known writer of N6-methyladenosine (m6A) on mRNA, a modification implicated in numerous aspects of RNA metabolism. Other RNA MTases target rRNA and tRNA to fine-tune translation.

Protein methyltransferases modify amino acid side chains, most notably lysines and arginines, altering protein function and interactions. Prominent families include lysine methyltransferases (SET-domain containing) and protein arginine methyltransferases (PRMTs), which play key roles in chromatin regulation and signaling.

MTases are central to development, genome defense, and epigenetic memory, and are targets in research, biotechnology, and medicine.