Beyond A, C, T, and G lies an epigenetic level of heritable control that has reached the forefront of biomedical research. Histone modification patterns, like multicolored highlighting in the genome's book of life, tell eukaryotic cells when to turn genes on and off, thus making sense of its DNA instructions. In 1993, researchers first pondered whether these alterations on N-terminal tails of histone proteins created a readable code1 (See also 5-Prime). Eight years later, groups from Austria and the United Kingdom wrote what many consider as the first complete chapter on the histone code hypothesis.2,3
Using mammalian cells and fission yeast, these two groups built on findings that histone methyltransferase SU(VAR)3-9 and its yeast homolog, Clr4, specifically methylate the ninth lysine (K9) on histone H3's tail. This methylated lysine, and none other, acts as a binding site for heterochromatin protein HP1, which was long associated with silent heterochromatic regions of ...
