5-methylcytosine

5-Methylcytosine

Names
IUPAC name 4-amino-5-methyl-3H-pyrimidin-2-one
Identifiers
CAS Number	554-01-8 Y
3D model (Jmol)	Interactive image Interactive image
ChEBI	CHEBI:27551 Y
ChemSpider	58551 Y
ECHA InfoCard	100.008.236
KEGG	C02376 Y
MeSH	5-Methylcytosine
PubChem	65040
UNII	6R795CQT4H Y
InChI InChI=1S/C5H7N3O/c1-3-2-7-5(9)8-4(3)6/h2H,1H3,(H3,6,7,8,9) Y Key: LRSASMSXMSNRBT-UHFFFAOYSA-N Y InChI=1/C5H7N3O/c1-3-2-7-5(9)8-4(3)6/h2H,1H3,(H3,6,7,8,9) Key: LRSASMSXMSNRBT-UHFFFAOYAO
SMILES O=C1/N=C\C(=C(\N)N1)C Cc1cnc(=O)[nH]c1N
Properties
Chemical formula	C5H7N3O
Molar mass	125.13 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (what is YN ?)
Infobox references

5-Methylcytosine is a methylated form of the DNA base cytosine that may be involved in the regulation of gene transcription. When cytosine is methylated, the DNA maintains the same sequence, but the expression of methylated genes can be altered (the study of this is part of the field of epigenetics). 5-Methylcytosine is incorporated in the nucleoside 5-methylcytidine.

In 5-methylcytosine, a methyl group is attached to the 5th atom in the 6-atom ring (counting counterclockwise from the NH nitrogen at the six o'clock position, not the 2 o'clock). This methyl group distinguishes 5-methylcytosine from cytosine.

While trying to isolate the bacterial toxin responsible for tuberculosis, W.G. Ruppel isolated a novel nucleic acid named tuberculinic acid in 1898 from Tubercle bacillus. The nucleic acid was found to be unusual, in that it contained in addition to thymine, guanine and cytosine, a methylated nucleotide. In 1925, Johnson and Coghill successfully detected a minor amount of a methylated cytosine derivative as a product of hydrolysis of tuberculinic acid with sulfuric acid. This report was severely criticized because their identification based solely on the optical properties of the crystalline picrate, and other scientists failed to reproduce the same result. But the existence was ultimately proved a fact in 1948, when Hotchkiss separated the nucleic acids of DNA from calf thymus using paper chromatography, by which he detected a unique methylated cytosine, quite distinct from conventional cytosine and uracil. After seven decades, it turned out that it is also a common feature in different RNA molecules, although the precise role is uncertain.