5Formylcytosin

5-formylcytosine (5fC) is a modified base found in DNA. It is generated by the oxidation of 5-methylcytosine (5mC), another common DNA modification. This oxidation is primarily carried out by the Ten-Eleven Translocation (TET) family of enzymes. 5fC is considered an intermediate in the active demethylation pathway of DNA, meaning it can be further processed to restore cytosine. The subsequent steps involve the removal of the formyl group, leading to unmodified cytosine.

The presence and function of 5fC are of significant interest in epigenetics. While 5mC is traditionally associated with gene silencing, 5fC and its derivatives, such as 5-hydroxymethylcytosine (5hmC), are implicated in gene regulation and cellular differentiation. The levels and distribution of 5fC can vary across different cell types and in response to various biological stimuli. Aberrant levels of 5fC have been observed in certain diseases, including cancer, suggesting its potential role as a biomarker or therapeutic target. Research into the precise biological roles and mechanisms of action of 5fC is ongoing.