N2-methylguanine (N2-methylguanine) is an endogenous methylated nucleoside found in human fluids and a modified nucleoside.

N2-methylguanine is the principal kinetic barrier for reverse transcription in the 1340 bases proximal to the 5' end of E. coli 16S rRNA. Transcription intermediates correspond to attenuation at the positions of N2-methylguanine in the rRNA sequence. The relaxation time for elongation of the cDNA through m2G is approximately 3 min[1]. N2-methylguanine is found within both helical and looped regions of RNA secondary structure, and it can exist in either the s-cis or the s-trans rotamer. If there is a rotational preference for the methyl group, the effect of N2-methylguanine substitution may be specific to the sequence context depending upon which face of the base participates in hydrogen bonding[2].