N1methyladenine

N1-methyladenine, commonly abbreviated m1A, is a methylated derivative of the nucleobase adenine in which a methyl group is attached to the nitrogen at position 1 of the adenine ring. This modification alters the base’s hydrogen-bonding properties and can disrupt normal base pairing.

In DNA, m1A can arise as a lesion after exposure to alkylating agents and is considered mutagenic because it can block replication and transcription. Repair of m1A lesions involves oxidative demethylation by AlkB-family dioxygenases in some organisms, and can also engage base excision repair pathways in others. The efficiency and prevalence of repair can vary by organism and cellular context.

In RNA, N1-methyladenine is also found as a natural post-transcriptional modification in various RNAs. A well-characterized form is m1A58, a common tRNA modification that contributes to proper tRNA folding and structural stability near the anticodon region. Other RNA species, including rRNA and, in some organisms, mRNA, can bear m1A modifications as well. Methylation of N1 in RNA is installed by RNA methyltransferases, such as bacterial TrmI for certain tRNAs and the eukaryotic TRMT61/TRMT6 complex for others, depending on RNA type and organism.

Detection and analysis of m1A in nucleic acids rely on chromatographic and mass spectrometric methods, sometimes combined with chemical or enzymatic steps to distinguish m1A from unmodified adenine. The biological significance of m1A is an active area of study, particularly regarding its dynamic regulation by demethylases in RNA and the consequences of DNA m1A lesions for genome stability.