Histone code

These recruited proteins then act to alter chromatin structure actively or to promote transcription.

While it is accepted that modifications (such as methylation, acetylation, ADP-ribosylation, ubiquitination, citrullination, SUMO-ylation[2] and phosphorylation) to histone tails alter chromatin structure, a complete understanding of the precise mechanisms by which these alterations to histone tails influence DNA-histone interactions remains elusive.

To give an idea of this complexity, histone H3 contains nineteen lysines known to be methylated—each can be un-, mono-, di- or tri-methylated.

[16] Mass spectrometry-based top-down proteomics has provided more insight into these patterns by being able to discriminate single molecule co-occurrence from co-localization in the genome or on the same nucleosome.

[17] A variety of approaches have been used to delve into detailed biochemical mechanisms that demonstrate the importance of interplay between histone modifications.