Histone modifying enzymes: The Writers
Post-translational modification of histones is a function of various enzymes that catalyse the addition of various chemical groups e.g. acetyl-, methyl-, phosphate-, ubiquitin- etc. from one substrate to another. Predominant targets for acetylation and methylation are the Lysine and Arginine residues present in the Histone peptides. Phosphorylation occurs at Serine/Threonine/Tyrosine residues. Writers have characteristic distinction wherein some are ubiquitously expressed in all cell types and some show tissue-specific expression. These enzymes have associated domains to recognise histone substrates.
We found 100 unique enzymes that belong to 8 different categories of writers. The important categories of this large group are Histone acetyltransferases (HAT/KAT), Histone methyltransferases (HMT/KMT), Kinases, Ubiquitinases etc. Many of these writers have other non-histone targets as well. Hence these may contribute towards regulation of any cellular process by more than one mechanism.Types of Writers Arginine deiminases, Arginine methyltransferases, Lysine acetyltransferases, Lysine biotinases, Lysine methyltransferases, Lysine ribosylases, Lysine ubiquitinases, Serine/threonine/tyrosine kinases