Histone methylation
Encyclopedia
Histone methylation is the modification of certain amino acids in a histone
protein by the addition of one, two, or three methyl groups. In the cell nucleus, DNA is wound around histones. Methylation and demethylation of histones turns the genes in DNA "off" and "on", respectively, either by loosening their tails, thereby allowing transcription factors and other proteins to access the DNA, or by encompassing their tails around the DNA, thereby restricting access to the DNA. This is true in most cases.
and affects its interactions with other proteins.
Histone
In biology, histones are highly alkaline proteins found in eukaryotic cell nuclei that package and order the DNA into structural units called nucleosomes. They are the chief protein components of chromatin, acting as spools around which DNA winds, and play a role in gene regulation...
protein by the addition of one, two, or three methyl groups. In the cell nucleus, DNA is wound around histones. Methylation and demethylation of histones turns the genes in DNA "off" and "on", respectively, either by loosening their tails, thereby allowing transcription factors and other proteins to access the DNA, or by encompassing their tails around the DNA, thereby restricting access to the DNA. This is true in most cases.
Function
This modification alters the properties of the nucleosomeNucleosome
Nucleosomes are the basic unit of DNA packaging in eukaryotes, consisting of a segment of DNA wound around a histone protein core. This structure is often compared to thread wrapped around a spool....
and affects its interactions with other proteins.
- Histone methylation is in general associated with transcriptional repressionRepressorIn molecular genetics, a repressor is a DNA-binding protein that regulates the expression of one or more genes by binding to the operator and blocking the attachment of RNA polymerase to the promoter, thus preventing transcription of the genes. This blocking of expression is called...
. - However, methylation of some lysineLysineLysine is an α-amino acid with the chemical formula HO2CCH4NH2. It is an essential amino acid, which means that the human body cannot synthesize it. Its codons are AAA and AAG....
and arginineArginineArginine is an α-amino acid. The L-form is one of the 20 most common natural amino acids. At the level of molecular genetics, in the structure of the messenger ribonucleic acid mRNA, CGU, CGC, CGA, CGG, AGA, and AGG, are the triplets of nucleotide bases or codons that codify for arginine during...
residues of histones results in transcriptional activation. Examples include methylation of lysine 4 of histone 3 (H3K4), and arginine (R) residues on H3 and H4Histone H4Histone H4 is one of the 5 main histone proteins involved in the structure of chromatin in eukaryotic cells. Featuring a main globular domain and a long N terminal tail, H4 is a structural component of the nucleosome, and is subject to covalent modification, including acetylation and methylation,...
.
See also
- methylationMethylationIn the chemical sciences, methylation denotes the addition of a methyl group to a substrate or the substitution of an atom or group by a methyl group. Methylation is a form of alkylation with, to be specific, a methyl group, rather than a larger carbon chain, replacing a hydrogen atom...
- Histone methyltransferaseHistone methyltransferaseHistone methyltransferases are enzymes, histone-lysine N-methyltransferase and histone-arginine N-methyltransferase, that catalyze the transfer of one to three methyl groups from the cofactor S-Adenosyl methionine to lysine and arginine residues of histone proteins...
- Histone acetylation and deacetylationHistone acetylation and deacetylationIn histone acetylation and deacetylation, the histones are acetylated and deacetylated on lysine residues in the N-terminal tail and on the surface of the nucleosome core as part of gene regulation. These reactions are typically catalyzed by enzymes with "histone acetyltransferase" or "histone...