histone


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histone

(hĭs`tōn), any of a class of proteinprotein,
any of the group of highly complex organic compounds found in all living cells and comprising the most abundant class of all biological molecules. Protein comprises approximately 50% of cellular dry weight.
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 molecules found in the chromosomes of eukaryotic cellscell,
in biology, the unit of structure and function of which all plants and animals are composed. The cell is the smallest unit in the living organism that is capable of integrating the essential life processes. There are many unicellular organisms, e.g.
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. They complex with the DNA (see nucleic acidnucleic acid,
any of a group of organic substances found in the chromosomes of living cells and viruses that play a central role in the storage and replication of hereditary information and in the expression of this information through protein synthesis.
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) and pack the DNA into tight masses of chromatin, which have the structure of coiled coils, much like a tangled telephone cord. The molecules are strongly basic and of relatively small size. They also serve a function in the transcription of DNA. The histones are rich in the amino acids argininearginine
, organic compound, one of the 20 amino acids commonly found in animal proteins. Only the l-stereoisomer participates in the biosynthesis of proteins.
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 and lysinelysine
, organic compound, one of the 20 amino acids commonly found in animal proteins. Only the l-stereoisomer appears in mammalian protein.
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; the five major subtypes of the class differ from one another chiefly in the relative amounts of these two amino acids. They have been greatly conserved during evolution, histone structures vary little in a wide range of organisms.

histone

[′hi‚stōn]
(biochemistry)
Any of the strong, soluble basic proteins of cell nuclei that are precipitated by ammonium hydroxide.
References in periodicals archive ?
They expected that yeast genetically engineered to carry fewer copies of certain histone genes than normal or control yeast would have chromatin changes that would result in the yeast living less than controls.
(11) These HDACIs possess specific structural components that trigger diverse functions like interruption in the cell cycle, angiogenesis, and immunomodulation by acting on histone and non-histone proteins.
In this research study, Celine Tiffon examines the effects of the differentiating histone deacetylase inhibitor Trichostatin A (TSA) in human pancreatic cancer cell lines, representing different tumor grades.
In addition to cytosine methylation, post-translational modifications taking place in the histone subunits composing the histone octamer also contribute to the definition of gene expression patterns.
"Conceptually, we could use the modification, which is the methylation of adenosine residue, as a 'code' in mRNA to target histone modifications to turn gene on or off," Zhao said.
Histone deacetylase inhibitors have been observed to enhance apoptosis of cancer cells induced by several chemotherapeutic agents including gemcitabine [43,48-53].
Although histone proteins play an important role in DNA transcription, the participation of HATs and HDACs that form part of the transcription initiation complex with transcription factors and regulate histone proteins has not been fully investigated in the brain.
Histone acetylation is preferentially carried out on specific lysine: for instance, histone H3 is mainly acetylated in positions 9, 14, 18, and 23, while the lysine of histone H4 that are preferentially acetylated are in positions 5, 8, 12, and 16.
Huang and Akbarian found an average 8-fold deficit in repressive chromatin-associated DNA methylation at GAD1 promoters in patients with schizophrenia [30] and it has been shown that histone 3 (H3), one of the histone proteins, was particularly dysregulated in schizophrenia patients [31].
The adding or removing of histone marks is carried out by a group of enzymes named (1) "writers," responsible for adding ("writing") different epigenetic marks such as HAT (histone acetyltransferase), which adds acetyl groups to histone tails, (2) "erasers," responsible for the removal of epigenetic marks of the histone, such as histone deacetylases (HDACs) or histone demethylases (HDMs), and (3) "readers," whose function is to recognize the different epigenetic marks added in the histones.
Acetylation and deacetylation of histones are controlled by histone acetyltransferases (HAT) and histone deacetylases (HDACs), respectively.