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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2012/09/03 09:05:20」(JST)

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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 carbon atom (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.

In vivo

5-Methylcytosine is an epigenetic modification formed by the action of DNA methyltransferases.

The function of this chemical varies significantly among species:^[1]

In bacteria, 5-methylcytosine can be found at a variety of sites, and is often used as a marker to protect DNA from being cut by native methylation-sensitive restriction enzymes.
In plants, 5-methylcytosine occurs at CpG, CpHpG and CpHpH sequences (where H = A, C or T).
In fungi and animals, 5-methylcytosine predominantly occurs at CpG dinucleotides. Most eukaryotes methylate only a small percentage of these sites, but 70-80% of CpG cytosines are methylated in vertebrates.

While spontaneous deamination of cytosine forms uracil, which is recognized and removed by DNA repair enzymes, deamination of 5-methylcytosine forms thymine. This conversion of a DNA base from cytosine (C) to thymine (T) can result in a transition mutation. In addition, active enzymatic deamination of cytosine or 5-methylcytosine by the APOBEC family of cytosine deaminases could have beneficial implications on various cellular processes as well as on organismal evolution.^[2] The implications of deamination on 5-hydroxymethylcytosine, on the other hand, remains less understood.

In vitro

The NH₂ group can be removed (deamination) from 5-methylcytosine to form thymine with use of reagents such as nitrous acid; cytosine deaminates to uracil under similar conditions.

Deamination of 5-methylcytosine to thymine

5-Methylcytosine is resistant to deamination by bisulfite treatment, which deaminates cytosine residues. This property is often exploited to analyze DNA cytosine methylation patterns with bisulfite sequencing.^[3]

References

^ Colot V, Rossignol JL (1999). "Eukaryotic DNA methylation as an evolutionary device". Bioessays 21 (5): 402–411. doi:10.1002/(SICI)1521-1878(199905)21:5<402::AID-BIES7>3.0.CO;2-B. PMID 10376011.
^ Chahwan R., Wontakal S.N., and Roa S. (2010). "Crosstalk between genetic and epigenetic information through cytosine deamination". Trends in Genetics 26 (10): 443–448. doi:10.1016/j.tig.2010.07.005. PMID 20800313.
^ Clark SJ, Harrison J, Paul CL, Frommer M (1994). "High sensitivity mapping of methylated cytosines". Nucleic Acids Res. 22 (15): 2990–2997. doi:10.1093/nar/22.15.2990. PMC 310266. PMID 8065911. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=310266.

Literature

Griffiths, Anthony J. F. (1999). An Introduction to genetic analysis. San Francisco: W.H. Freeman. Chapter 15: Gene Mutation. ISBN 0-7167-3520-2. (available online at the United States National Center for Biotechnology Information)

English Journal

Cytosine modifications in myeloid malignancies.

Meldi KM1, Figueroa ME1.
Pharmacology & therapeutics.Pharmacol Ther.2015 Aug;152:42-53. doi: 10.1016/j.pharmthera.2015.05.002. Epub 2015 May 5.
Aberrant DNA methylation is a hallmark of many cancers, including the myeloid malignancies acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS). The discovery of TET-mediated demethylation of 5-methylcytosine (5mC) and technological advancements in next-generation sequencing have permitt
PMID 25956466

Age-Dependent Levels of 5-Methyl-, 5-Hydroxymethyl-, and 5-Formylcytosine in Human and Mouse Brain Tissues.

Wagner M1, Steinbacher J1, Kraus TF2, Michalakis S3, Hackner B1, Pfaffeneder T1, Perera A3, Müller M1, Giese A2, Kretzschmar HA2, Carell T4.
Angewandte Chemie (International ed. in English).Angew Chem Int Ed Engl.2015 Jul 3. doi: 10.1002/anie.201502722. [Epub ahead of print]
The absolute levels of 5-hydroxymethylcytosine (hmC) and 5-methylcytosine (mC) in human brain tissues at various ages were determined. Additionally, absolute levels of 5-formylcytosine (fC) in adult individuals and cytosine modification levels in sorted neurons were quantified. These data were compa
PMID 26137924

Lead exposure induces changes in 5-hydroxymethylcytosine clusters in CpG islands in human embryonic stem cells and umbilical cord blood.

Sen A1, Cingolani P, Senut MC, Land S, Mercado-Garcia A, Tellez-Rojo MM, Baccarelli AA, Wright RO, Ruden DM.
Epigenetics : official journal of the DNA Methylation Society.Epigenetics.2015 Jul 3;10(7):607-21. doi: 10.1080/15592294.2015.1050172.
Prenatal exposure to neurotoxicants such as lead (Pb) may cause stable changes in the DNA methylation (5mC) profile of the fetal genome. However, few studies have examined its effect on the DNA de-methylation pathway, specifically the dynamic changes of the 5-hydroxymethylcytosine (5hmC) profile. Th
PMID 26046694

Japanese Journal

組織化学的アプローチよる転写調節解析 : 転写調節因子とエピジェネティック因子の局在証明法(組織細胞化学技法の基本をじっくりと、確実に)

小路武彦
組織細胞化学 2013, 77-88, 2013-07-10
NAID 110009685979

Tet family of 5-methylcytosine dioxygenases in mammalian development (Special Section on Epigenomics : biological understanding and clinical application)

Zhao Hongbo,Chen Taiping
Journal of human genetics 58(7), 421-427, 2013-07
NAID 40019704952

Design of Hydroxymethylcytosine-distinguisable Phosphopeptide from Methylcytosine in DNA

NOMURA Akiko,SUGIZAKI Kaori,YANAGISAWA Hiroyuki,OKAMOTO Akimitsu
Peptide science : proceedings of the ... Japanese Peptide Symposium 2012, 305-308, 2013-03-01
NAID 10031161637

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★リンクテーブル★

リンク元

「m5C」

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

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同: 5-methylcytosine

同: 5-methylcytosine

[0] Colot V, Rossignol JL (1999). "Eukaryotic DNA methylation as an evolutionary device". Bioessays 21 (5): 402–411. doi:10.1002/(SICI)1521-1878(199905)21:5<402::AID-BIES7>3.0.CO;2-B. PMID 10376011.

[1] Chahwan R., Wontakal S.N., and Roa S. (2010). "Crosstalk between genetic and epigenetic information through cytosine deamination". Trends in Genetics 26 (10): 443–448. doi:10.1016/j.tig.2010.07.005. PMID 20800313.

[2] Clark SJ, Harrison J, Paul CL, Frommer M (1994). "High sensitivity mapping of methylated cytosines". Nucleic Acids Res. 22 (15): 2990–2997. doi:10.1093/nar/22.15.2990. PMC 310266. PMID 8065911. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=310266.

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5-methylcytosine