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histone

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histone (hĭs`tōn), any of a class of protein protein, 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 cells cell, 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 acid nucleic 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 arginine arginine (är`jənĭn), organic compound, one of the 20 amino acids commonly found in animal proteins.
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 and lysine lysine (lī`sēn), organic compound, one of the 20 amino acids commonly found in animal proteins.
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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

Any of a class of rather simple proteins occurring in cell nuclei and in combination with DNA to form nucleoproteins. They can be obtained from both plants and animals. Unlike most proteins, they dissolve readily in water. They were discovered c. 1884.



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On the other hand, acetyl groups attaching to histones, the chemical core of chromosomes, usually turn genes on.
Romidepsin is a novel agent in a new class of anti-cancer drugs known as histone deacetylase inhibitors.
 
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