| 5-Methylcytosine | |
|---|---|
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| IUPAC name |
4-amino-5-methyl-3H-pyrimidin-2-one
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| Identifiers | |
| CAS number | 554-01-8  |
| PubChem | 65040 |
| MeSH | 5-Methylcytosine |
| SMILES |
CC1=C(NC(=O)N=C1)N
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| Properties | |
| Molecular formula | C5H7N3O |
| Molar mass | 125.129 |
| (what is this?) (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
5-Methylcytosine is a methylated form of cytosine in which a methyl group is attached to carbon 5, altering its structure without altering its base-pairing properties.
Contents |
In vivo
5-Methylcytosine is an epigenetic modification formed by the action of DNA methyltransferases. Its function 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, CpNpG and CpNpN sequences (where N = A, C or T).
- In fungi and animals, 5-methylcytosine predominantly occurs at CpG dinucleotides. Although most eukaryotes methylate only a small percentage of these sites, in vertebrates 70-80% of CpG cytosines are methylated.
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 vitro
5-Methylcytosine can be deaminated to form thymine with use of reagents such as nitrous acid; cytosine deaminates to uracil under similar conditions.
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.[2]
Additional images
References
- ^ Colot V, Rossignol JL (1999). "Eukaryotic DNA methylation as an evolutionary device". Bioessays 21 (5): 402–11. doi:. PMID 10376011.
- ^ Clark SJ, Harrison J, Paul CL, Frommer M (1994). "High sensitivity mapping of methylated cytosines". Nucleic Acids Res. 22 (15): 2990–7. doi:. PMID 8065911.
- 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)
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