Protein Domain : Histone H3-K9 methyltransferase, plant IPR025794

Type	Family
Description	In general, members of this family methylate 'Lys-9' of histone H3. It also methylates 'Lys-27' of histone H3 [ ] and 'Lys-20' of H4, and cytosine []. H3 'Lys-9' methylation represents a specific tag for epigenetic transcriptional repression []. This enzyme plays a central role in gene silencing []. The silencing mechanism via DNA CpNpG methylation requires the targeting of chromomethylase CMT3 to methylated histones, probably through an interaction with an heterochromatin protein 1-like adapter. Arabidopsis homologue SUVH4 is directly required for the maintenance of the DNA CpNpG and asymmetric methylation. It is also involved in the silencing of transposable elements [, , , , ].Methyltransferases (EC [intenz:2.1.1.-]) constitute an important class of enzymes present in every life form. They transfer a methyl group most frequently from S-adenosyl L-methionine (SAM or AdoMet) to a nucleophilic acceptor such as oxygen leading to S-adenosyl-L-homocysteine (AdoHcy) and a methylated molecule [, , ]. All these enzymes have in common a conserved region of about 130 amino acid residues that allow them to bind SAM []. The substrates that are methylated bythese enzymes cover virtually every kind of biomolecules ranging from small molecules, to lipids, proteins and nucleic acids [ , , ]. Methyltransferase are therefore involved in many essential cellular processes including biosynthesis, signal transduction, protein repair, chromatin regulation and gene silencing [, , ]. More than 230 families of methyltransferases have been described so far, of which more than 220 use SAM as the methyl donor.
Short Name	H3-K9-MeTrfase_plant