Abstract
The prevalent DNA modification in higher organisms is the methylation of cytosine to 5-methylcytosine (5mC), which is partially converted to 5-hydroxymethylcytosine (5hmC) by the Tet (ten eleven translocation) family of dioxygenases. Despite their importance in epigenetic regulation, it is unclear how these cytosine modifications are reversed. Here, we demonstrate that 5mC and 5hmC in DNA are oxidized to 5-carboxylcytosine (5caC) by Tet dioxygenases in vitro and in cultured cells. 5caC is specifically recognized and excised by thymine-DNA glycosylase (TDG). Depletion of TDG in mouse embyronic stem cells leads to accumulation of 5caC to a readily detectable level. These data suggest that oxidation of 5mC by Tet proteins followed by TDG-mediated base excision of 5caC constitutes a pathway for active DNA demethylation.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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5-Methylcytosine / metabolism
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Animals
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Cell Line
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Cytosine / analogs & derivatives*
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Cytosine / metabolism
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DNA / metabolism*
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DNA Methylation
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism*
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Dioxygenases
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Embryonic Stem Cells
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HEK293 Cells
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Humans
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Induced Pluripotent Stem Cells / metabolism
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Mice
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Oxidation-Reduction
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Proto-Oncogene Proteins / genetics
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Proto-Oncogene Proteins / metabolism*
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RNA, Small Interfering
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Thymine DNA Glycosylase / genetics
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Thymine DNA Glycosylase / metabolism*
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Transfection
Substances
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5-carboxylcytosine
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DNA-Binding Proteins
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Proto-Oncogene Proteins
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RNA, Small Interfering
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TET1 protein, mouse
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5-hydroxymethylcytosine
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5-Methylcytosine
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Cytosine
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DNA
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Dioxygenases
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Tet2 protein, mouse
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Tet3 protein, mouse
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Thymine DNA Glycosylase