Chromatin modification proteins contribute to not only chromatin

The cell transcription is regulated by several modifications of chromatin that consists of DNA and core histones. These modifications include methylation of DNA, and methylation, acetylation, phosphorylation,ubiquitination of histones. There have been discovered diverse modification factors that have specific enzymatic activities for catalyzing the modifications shown above. However, these factors contribute not only to the modification of chromatin components but also to that of other proteins which are not directly associated with chromatin. For example, STAT3, a signal transducer protein, is methylated by a histone modification factor, EZH2, although EZH2 was originally identified as a histone H3 lysine 27 methyltransferase. Moreover, there are many examples that chromatin modification proteins contribute to the modification of the other kinds of protein. It is interesting that some viruses also utilize cellular histone modification enzymes for the modification of their viral proteins to acquire the efficient viral propagation.