Regulation and function of DNA and histone methylations.

Cell type specification, transcription factor binding site selection and transcriptional regulation are specific processes that require a fine regulation that cannot be simply explained by the mere DNA sequence. Similarly, genome stability, damage response as well as genomic imprints and X-chromosome inactivation are all processes that involve an epigenetic level of regulation. This includes the activity of several enzymes that act in concert to "place" or "remove" specific modifications shaping cells epigenomes with posttranslational modifications of histone proteins and modifications of DNA cytosine residues. In this review, we discuss the role of histone and DNA methylation in regulating different cellular processes with a particular emphasis on transcriptional regulation and on the mechanistic insights behind different enzymatic activities with a perspective towards their implications in human diseases.