5-Hydroxymethylcytosine

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5-Hydroxymethylcytosine
IUPAC name

6-Amino-5-(hydroxymethyl)-1H-pyrimidin-2-one
Identifiers
CAS number 1123-95-1 N
PubChem 70751
ChemSpider 63916 YesY
Jmol-3D images Image 1
Image 2
Properties
Molecular formula C5H7N3O2
Molar mass 141.13 g/mol
 N (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

5-Hydroxymethylcytosine is a DNA pyrimidine nitrogen base. It is formed from the DNA base cytosine by adding a methyl group and then a hydroxy group. It is important in epigenetics, because the hydroxymethyl group on the cytosine can possibly switch a gene on and off. It was first seen in bacteriophages in 1952.[1][2] However, in 2009 it was found to be abundant in human and mouse brains,[3] as well as in embryonic stem cells.[4] In mammals, it can be generated by oxidation of 5-methylcytosine, a reaction mediated by the Tet family of enzymes. Its molecular formula is C5H7N3O2.[5]

Contents

[edit] Localization

Every mammalian cell seems to contain 5-Hydroxymethylcytosine, but the levels vary significantly depending on the cell type. The highest levels are found in neuronal cells of the central nervous system.[6][7][8] The amount of hydroxymethylcytosine increases with age, as shown in mouse hippocampus and cerebellum.[6][9]

[edit] Function

The exact function of this nitrogen base is still not fully elucidated, but it is thought that it may regulate gene expression or prompt DNA demethylation. This hypothesis is supported by the fact that artificial DNA that contains 5-hydroxymethylcytosines can be converted into unmodified cytosines once introduced into mammalian cells.[10] Additionally, 5-Formylcytosine, an oxidation product of 5-Hydroxymethylcytosine and possible intermediate of an oxidative demethylation pathway was detected in DNA from embryonic stem cells.[11] Interestingly, no significant amounts of putative demethylation intermediates could be detected in mouse tissue.[8] 5-Hydroxymethylcytosine may be especially important in the central nervous system, as it is found in very high levels there.[8]

[edit] History

5-Hydroxymethylcytosine was observed by Skirmantas Kriaucionis, an associate at the Heintz lab, who was looking for levels of 5-methylcytosine in two different neurons. He discovered a significant amount of an unknown substance instead, and after conducting several tests, discovered that the substance was 5-hydroxymethylcytosine.[12]

The lab of L. Aravind used bioinformatic tools to predict that the Tet family of enzymes would likely oxidize 5-methylcytosine to 5-hydroxymethylcytosine.[13] This was demonstrated in vitro and in live human and mouse cells by scientists working in the labs of Anjana Rao and David Liu.

5-Hydroxymethylcytosine was originally observed in mammals in 1972 by R. Yura,[14] but this initial finding is dubious. Yura found 5-hmC present at extremely high levels in rat brain and liver, completely supplanting 5-methylcytosine. This contradicts all research conducted on mammalian DNA composition conducted before and since, including the Heintz and Rao papers, and another group was unable to reproduce Yura's result.[15]

With the discovery of 5-hydroxymethylcytosine some concerns have been raised regarding DNA methylation studies using the bisulfite sequencing technique.[16] 5-hydroxymethylcytosine has been shown to behave like its precursor, 5-methylcytosine, in bisulfite conversion experiments.[17] Therefore, bisulfite sequencing data may need to be revisited to verify whether the detected modified base is 5-methylcytosine or 5-hydroxymethylcytosine.

[edit] References

  1. ^ Warren RA (1980). "Modified bases in bacteriophage DNAs". Annu. Rev. Microbiol. 34: 137–158. doi:10.1146/annurev.mi.34.100180.001033. PMID 7002022. 
  2. ^ Wyatt GR, Cohen SS (December 1952). "A new pyrimidine base from bacteriophage nucleic acids". Nature 170 (4338): 1072–1073. doi:10.1038/1701072a0. PMID 13013321. 
  3. ^ Kriaucionis S, Heintz N (May 2009). "The nuclear DNA base 5-hydroxymethylcytosine is present in Purkinje neurons and the brain". Science 324 (5929): 929–930. doi:10.1126/science.1169786. PMID 19372393. 
  4. ^ Tahiliani M et al. (May 2009). "Conversion of 5-methylcytosine to 5-hydroxymethylcytosine in mammalian DNA by MLL partner TET1". Science 324 (5929): 930–935. doi:10.1126/science.1170116. PMC 2715015. PMID 19372391. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2715015. 
  5. ^ 5-Hydroxymethylcytosine, nextbio.com
  6. ^ a b Münzel M et al. (July 2010). "Quantification of the Sixth DNA Base Hydroxymethylcytosine in the Brain". Angew. Chem. Int. Ed. 49 (31): 5375–5377. doi:10.1002/anie.201002033. 
  7. ^ Szwagierczak A et al. (October 2010). "Sensitive Enzymatic Quantification of 5-Hydroxymethylcytosine in Genomic DNA". Nucleic Acids Res. 38 (19): e181. doi:10.1093/nar/gkq684. PMC 2965258. PMID 20685817. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2965258. 
  8. ^ a b c Globisch D et al. (December 2010). Croft, Anna Kristina. ed. "Tissue Distribution of 5-Hydroxymethylcytosine and Search for Active Demethylation Intermediates". PLoS ONE 5 (12): e15367. doi:10.1371/journal.pone.0015367. PMC 3009720. PMID 21203455. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3009720. 
  9. ^ Song C-X et al. (December 2010). "S elective chemical labeling reveals the genome-wide distribution of 5-hydroxymethylcytosine". Nat. Biotech. 29 (1): 68–72. doi:10.1038/nbt.1732. 
  10. ^ Guo, Junjie U.; Su, Yijing, Zhong, Chun, Ming, Guo-li, Song, Hongjun (1 April 2011). "Hydroxylation of 5-Methylcytosine by TET1 Promotes Active DNA Demethylation in the Adult Brain". Cell 145 (3): 423–434. doi:10.1016/j.cell.2011.03.022. PMC 3088758. PMID 21496894. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3088758. 
  11. ^ Pfaffeneder, Toni; Hackner, Benjamin, Truss, Matthias, Münzel, Martin, Müller, Markus, Deiml, Christian A., Hagemeier, Christian, Carell, Thomas (30 June 2011). "The Discovery of 5-Formylcytosine in Embryonic Stem Cell DNA". Angew. Chem., Int. Ed.. doi:10.1002/anie.201103899. PMID 21721093. 
  12. ^ A, T, G, C and What?, popsci.com
  13. ^ Iyer LM et al. (June 2009). "Prediction of novel families of enzymes involved in oxidative and other complex modifications of bases in nucleic acids". Cell Cycle 8 (11): 1698–1710. doi:10.4161/cc.8.11.8580. PMC 2995806. PMID 19411852. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2995806. 
  14. ^ Penn NW, Suwalski R, O'Riley C, Bojanowski K, Yura R (February 1972). "The presence of 5-hydroxymethylcytosine in animal deoxyribonucleic acid". Biochem. J. 126 (4): 781–790. PMC 1178489. PMID 4538516. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1178489. 
  15. ^ Kothari, Rm; Shankar, V (May 1976). "5-Methylcytosine content in the vertebrate deoxyribonucleic acids: species specificity". Journal of molecular evolution 7 (4): 325–329. doi:10.1007/BF01743628. ISSN 0022-2844. PMID 933178. 
  16. ^ 5 hydroxymethylcytosine analysis techniques
  17. ^ Jin SG et al. (Jun 2010) "Examination of the specificity of DNA methylation profiling techniques towards 5-methylcytosine and 5-hydroxymethylcytosine." Nucleic Acids Res. 2010 Jun 1;38(11):e125

[edit] External links

[edit] See also

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