Histone classification

Histones Small chromosomal proteins (approx 12-20 kD) possessing an open, unfolded structure and attached to the DNA in cell nuclei by ionic linkages. Classification into the various types (designated histone I, histone II, etc.) is based on the relative amounts of arginine and lysine in each. [NIH]... 

Initial studies in mice lead to a classification of histone variants into three main subgroups on the basis of their expression and integration into chromosomes (Isenberg 1979). These are DNA replication-dependent, replication-independent. 

Eomeris E, Binda C, Vanoni MA, BattagUoli E, Mattevi A (2005) Human histone demethylase LSDl reads the histone code. J Biol Chem 280 41360-41365 Erye RA (2000) Phylogenetic classification of prokaryotic and eukaryotic Sir2-like proteins. Biochem Biophys Res Commun 273 793—798... 

Histones are highly basic, small, compact proteins, with a high affinity for DNA. They occur naturally, attached to the DNA of cell nuclei by ionic linkages. Their classification is based on the relative amounts of lysine and arginine. The galactosylated, lysine-rich histone HI was found to be superior to the H2-H4 histones as a DNA carrier for liver gene delivery (53). 

In a cell cycle assay, the percentage of cells in each cell cycle stage is the most crucial measurement. Cells can be classified into Glor G2 phase by their DNA content, the M phase (mitotic or interphase) by the phospho-histone H3 mitotic marker, and the S phase by a pulsed label with dU to detect DNA synthesis. Each cell has four intensity parameters and has to be classified into the Gl, G2, S, or M phase based on these parameters. Because we are potentially dealing with billions of cells, cell cycle classification must be automated. 

Table VIII. Classification of Acetylation Sites in Trout Testis Histones (103)...

This classification of the histones has been accepted and confirmed by many other workers. 

In the past, globular proteins were classified according to their solubilities and some of their chemical characteristics. This classification is no longer satisfactory, especially because the classes cannot be defined precisely enough. We want to distinguish only among (1) histones, (2) albumins, and (3) globulins. 

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