How can nucleotides and proteins be modified into epigenetic tags?
DNA frequently becomes methylated by an enzyme called DNA methyltransferase. DNA methylation is a type of chemical modification which involves the addition of a methyl group to the carbon-5 of the cytosine pyrimidine ring. This methyl group can be sensed by proteins which then themselves modify other proteins posttranslationally. The pattern of posttranslational change creates changes in electric charge within chromatin and this leads to different degrees of chromatin condensation. It also determines whether genes can be transcribed or become silent within highly compacted chromatin. Silence of genes means, that their encoded genetic information is not transribed into mRNA and subsequently it will not be translated into protein molecules. There are many ways of how electric charges between nucleotide molecules and proteins can be altered. These variances of charge are identical with what people call epigenetic tags. In addition to DNA methylation (i.e. a form of alkylation), proteins c
