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 ?
The findings are the first to illustrate crosstalk between mRNA and histone modifications, and may lead to new ways to target genes in the brain, Zhao said.
Epigenetic mechanisms include changes in DNA methylation, histone modifications, and microRNA (miRNA) expression.
As described briefly above, histone modifications are involved in the regulation of gene expression via chromatin remodeling, which determines the accessibility of transcription factors to their binding sites.
12) Regulatory RNA is required for proper maintenance of DNA methylation and some histone modifications.
Global histone modification pattern associated with recurrence and disease-free survival in non-small cell lung cancer patients.
Cancer cells often show global DNA hypomethylation, a modification associated with chromosomal instability, hypermethylation at promoter CpG sites, which causes aberrant gene silencing, and disruption in the normal pattern of covalent histone modifications.
Epigenetic histone modification and cardiovascular lineage programming in mouse embryonic stem cells exposed to laminar shear stress.
Histone modifications around individual BDNF gene promoters in prefrontal cortex are associated with extinction of conditioned fear.
Further investigation revealed that HDA6 binds directly to transposons and silences their activity through specific histone modifications, and that another enzyme, the DNA methyltransferase MET1, cooperates with HDA6 in this gene silencing.
These epigenetic mechanisms include crosstalk between DNA methylation, histone modification and other components of chromatin higher-order structure, and lead to the regulation of gene transcription.
An important aspect highlighted and reviewed is that both genetic and the epigenetic effects of environment (through DNA methylation, histone modification and micro RNA) are passed down to the progeny and future generations forming the underlying cause for the burden of many chronic debilitating diseases seen in the offspring.
DNA methylation and histone modification have recently become targets for development of new drugs such as azacitidine (Vidaza, Mylosar), which has been approved for the treatment of myelodys-plastic syndromes, and zebularine, which is under investigation in the treatment of cutaneous T-cell lymphomas.

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