Histone-modifying enzymes

Histone-modifying enzymes are <a href="/facts/Enzyme/DSI1Fh7y">enzymes</a> involved in the <a href="/facts/Post-translational_modification/KMUayTIc">modification</a> of <a href="/facts/Histone/krb5VJfp">histone</a> substrates after <a href="/facts/Translation_(biology)/JcPC1rth">protein translation</a> and affect cellular processes including <a href="/facts/Gene_expression/alCPohLR">gene expression</a>. To safely store the <a href="/facts/Eukaryote/SkwyPLMA">eukaryotic</a> <a href="/facts/Genome/31Sm08JT">genome</a>, <a href="/facts/DNA/nB89Iauz">DNA</a> is wrapped around four core <a href="/facts/Histone/krb5VJfp">histone</a> <a href="/facts/Protein/Jxmagu3E">proteins</a> (H3, H4, H2A, H2B), which then join to form <a href="/facts/Nucleosome/HX5DR9bn">nucleosomes</a>. These nucleosomes further fold together into highly condensed <a href="/facts/Chromatin/ha0TJheJ">chromatin</a>, which renders the organism's genetic material far less accessible to the factors required for <a href="/facts/Transcription_(genetics)/bDgp9HDN">gene transcription</a>, <a href="/facts/DNA_replication/wrU6RuR3">DNA replication</a>, <a href="/facts/Genetic_recombination/uocNH0m7">recombination</a> and <a href="/facts/DNA_repair/hsURuYYq">repair</a>. Subsequently, eukaryotic organisms have developed intricate mechanisms to overcome this repressive barrier imposed by the chromatin through <a href="/facts/Histone_modification/krb5VJfp">histone modification</a>, a type of <a href="/facts/Post-translational_modification/KMUayTIc">post-translational modification</a> which typically involves <a href="/facts/Covalent_bond/EzMLf3Pz">covalently attaching</a> certain groups to histone residues. Once added to the histone, these groups (directly or indirectly) elicit either a loose and open histone conformation, <a href="/facts/Euchromatin/PHoEAn8F">euchromatin</a>, or a tight and closed histone conformation, <a href="/facts/Heterochromatin/frJ8HL41">heterochromatin</a>. Euchromatin marks active <a href="/facts/Transcription_(biology)/bDgp9HDN">transcription</a> and <a href="/facts/Gene_expression/alCPohLR">gene expression</a>, as the light packing of histones in this way allows entry for proteins involved in the transcription process. As such, the tightly packed heterochromatin marks the absence of current gene expression.
While there exist several distinct post-translational modifications for <a href="/facts/Histone/krb5VJfp">histones</a>, the four most common histone modifications include <a href="/facts/Histone_acetylation_and_deacetylation/jafcW82T">acetylation</a>, <a href="/facts/Histone_methylation/GP0gj9Av">methylation</a>, <a href="/facts/Protein_phosphorylation/4alcRDkM">phosphorylation</a> and <a href="/facts/Ubiquitination/hpulmU3m">ubiquitination</a>. Histone-modifying enzymes that induce a modification (e.g., add a <a href="/facts/Functional_group/GXkSPsjM">functional group</a>) are dubbed writers, while enzymes that revert modifications are dubbed erasers. Furthermore, there are many uncommon histone modifications including <a href="/facts/O-GlcNAc/0DYsUnnd">O-GlcNAcylation</a>, <a href="/facts/SUMO_protein/T5vYKlQd">sumoylation</a>, <a href="/facts/ADP-ribosylation/rv6QqIqv">ADP-ribosylation</a>, <a href="/facts/Citrullination/gsMUqv0n">citrullination</a> and <a href="/facts/Proline_isomerization/Lua79Tkm">proline isomerization</a>. For a detailed example of histone modifications in transcription regulation see <a href="/facts/RNA_polymerase_control_by_chromatin_structure/MK2kgybw">RNA polymerase control by chromatin structure</a> and table "<a href="/facts/Histone/krb5VJfp">Examples of histone modifications in transcriptional regulation</a>".

Histone-modifying enzymes open-in-new

Histone-modifying enzymes