Modified Forms of Cytosine in Eukaryotes: DNA (De)methylation and Beyond.

5-Methylcytosine (5mC) is an epigenetic mark known to contribute to the regulation of gene expression in a wide range of biological systems. Ten Eleven Translocation (TET) dioxygenases oxidize 5mC to 5-hydroxymethylcytosine, 5-formylcytosine, and 5-carboxylcytosine in metazoans and fungi. Moreover, two recent reports imply the existence of other species of modified cytosine in unicellular alga Chlamydomonas reinhardtii and malaria parasite Plasmodium falciparum. Here we provide an overview of the spectrum of cytosine modifications and their roles in demethylation of DNA and regulation of gene expression in different eukaryotic organisms.