1-Methylcytosine
1-Methylcytosine is a methylated form of the DNA base cytosine. The deoxyribonucleoside it forms is called N1-methyl-2'-deoxy-pseudocytidine.
In 1-methylcytosine, a methyl group is attached to the 1st atom in the 6-atom ring. This methyl group distinguishes 1-methylcytosine from cytosine. The location distinguishes it from the more common 5-methylcytosine.
1mC forms hydrogen bonds differently compared to cytosine because it attaches to the backbone sugar differently: at the C5 position as opposed to cytidine's C1 position, analogous to the difference between pseudouridine and uridine. It pairs with isoguanine in Artificially Expanded Genetic Information System DNA, replacing the unstable deoxyribonucleoside form of isocytosine.
History
Miriam Rossi worked on the refinement of the crystallographic structure of 1-methylcytosine.It was discovered as a stable replacement for 2'-deoxy-5-methylisocytidine in 2009.