N6metamethyladenosine

N6metamethyladenosine is a nonstandard term encountered in some discussions of RNA nucleotide modifications. In widely used nomenclature, the best characterized N6-substituted adenosine is N6-methyladenosine (m6A), a common internal modification of eukaryotic mRNA and various noncoding RNAs. The descriptor metamethyl may be used to indicate an additional methyl substitution at the N6 position, suggesting N6,N6-dimethyladenosine, but there is no established consensus. Consequently, the exact chemical form implied by N6metamethyladenosine can vary by source, and in some contexts the term may effectively refer to the canonical m6A or to a hypothetical di-methylated variant.

Chemically, the N6 position of adenine bears a site for exocyclic amine modification. Methylation at this position yields m6A; further methylation would introduce a second methyl group on the same nitrogen, potentially producing an N6,N6-dimethyl derivative. Such changes would alter hydrogen bonding, base pairing preferences, and local RNA structure, with possible consequences for recognition by RNA-binding proteins.

In terms of occurrence, m6A is widely distributed in higher eukaryotes and influences RNA metabolism, including splicing, export, translation, and decay. It is installed by the methyltransferase complex formed by METTL3 and METTL14, among others, and can be removed by demethylases such as FTO and ALKBH5. It is read by specific proteins, notably the YTH domain family, which mediate downstream effects. If N6metamethyladenosine refers to a noncanonical or di-methylated form, its biological roles would depend on the precise chemical state and recognition by the cellular machinery, and would require experimental validation.

Related topics include N6-methyladenosine (m6A), RNA modification, and the enzymes of the m6A-writing, -erasing, and -reading pathways.