Hydroxymethylation and tumors: can 5-hydroxymethylation be used as a marker for tumor diagnosis and treatment?

摘要

Chemical structures of 5-methylcytosine (5mC) and its oxidized modifications. Cytosine is converted to 5-methylcytosine by both DNMT1 and DNMT3. 5-Methylcytosine is oxidized by TET1, TET2, or TET3 to yield 5-hydroxymethylcytosine (5hmC). By a similar reaction, using the same enzymes, 5-hydroxymethylcytosine is further oxidized to 5-formylcytosine (5fC) and 5-carboxycytosine (5caC). Both 5-formylcytosine and 5-carboxycytosine are depyrimidated by the thymine DNA glycosylase (TDG) and processed by the base excision repair (BER) pathway. All these pathways could result in unmodified cytosine. ɑ-KG = ɑ-ketoglutaric acid; SA = succinic acid