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Mammalian Active DNA Demethylation
Activation-Induced cytidine Deaminase (AID) is an enzyme required for demethylation (removal of CpG methylation). Within the genome, DNA methylation is associated with epigenetic mechanisms and occurs at cytosine residues that are followed by guanines. This enzyme is also found expressed in primordial germ cells.
(a) The action of AID on 5-methylcytosine residues (white circles) in DNA (thick black line) gives rise to deaminated 5-methylcytosine, which can be bound by the repair glycosylase MBD4. Through yet-unknown further repair mechanisms, there is conversion into unmethylated cytosines, as shown by the disappearance of the white circles on the lower diagram. The canonical histones found in nucleosomes are colored in blue. In the accessibility model presented here, the presence (green circles) or absence of specific histone tail modifications and/or histone variants (pink spheres) guide the recruitment of the enzymes and other factors involved in the DNA demethylation. It is not yet known whether the requirement for elongator complex proteins is direct or whether they affect DNA demethylation indirectly, by a mechanism unrelated to chromatin.
(b) Protection against active DNA demethylation could be linked to the presence of specific histone modifications (red circles). Non-histone proteins could be involved in this process as well.
Reference
Sanz LA, Kota SK & Feil R. (2010). Genome-wide DNA demethylation in mammals. Genome Biol. , 11, 110. PMID: 20236475 DOI.
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| current | 13:40, 19 November 2010 | | 800 × 522 (63 KB) | S8600021 (talk | contribs) | ==Mammalian Active DNA Demethylation== Activation-Induced cytidine Deaminase (AID) is an enzyme required for demethylation (removal of CpG methylation). Within the genome, DNA methylation is associated with epigenetic mechanisms and occurs at cytosine re |
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