Some surveys had multiple iterations with only slight modifications – adding or removing one question, or slightly modifying wording in response to visitor feedback.
Transcription factors often work by recruiting enzymes that add modifications (e.g., acetyl groups or methyl groups) to or remove modifications from the outer parts of the histone molecules.
It is known that many histone modifications are dynamically regulated by enzymes which add or remove the chromatin modifications, with defects in either of these two functions resulting in incorrect activation or repression [ 1].
Histone modifications are catalysed by a large variety of histone-modifying enzymes, which are able to read, add or remove covalent modifications to histone proteins [ 42].
Key regulators of the epigenome are chromatin-modifying complexes that can add or remove covalent modifications to chromatin [ 175, 176].
So far dozens of genes are known to encode proteins that establish or remove histone modifications in the human genome.
Histone code is 'written' or 'erased' by enzymes that add or remove the modifications of histones (Goldberg et al., 2007; Kouzarides, 2007).
Failure to install or remove Ub modifications at the appropriate time can lead to the pathogenesis of a number of human diseases, including many cancers and neurological disorders.
Various histone-modifying enzymes able to add or remove chromatin modifications, including histone acetyltransferases (HATs), histone deacetylases (HDACs) and lysine methyltransferases, have been identified [ 3].
Perhaps most striking is that lipoylation itself, the proteins that add or remove the modification, as well as the proteins it decorates are all evolutionarily conserved from bacteria to humans, highlighting the importance of this essential cofactor.
