Abstract
Cytosine modification by AdoMet–dependent DNA methyltransferases is part of an epigenetic regulatory network in vertebrates. Here we show that, in the absence of AdoMet, bacterial cytosine-5 methyltransferases can catalyze condensation of aliphatic thiols and selenols to 5-hydroxymethylcytosine in DNA yielding 5-chalcogenomethyl derivatives. These new atypical reactions open new ways for sequence-specific derivatization and analysis of 5-hydroxymethylcytosine, a recently discovered nucleobase in mammalian DNA