Nonhistone protein

Chromatin consists of very long double-stranded DNA molecules and a nearly equal mass of rather small basic proteins termed histones as well as a smaller amount of nonhistone proteins (most of which are acidic and... 

When the histone octamer is mixed with purified, double-stranded DNA, the same x-ray diffraction pattern is formed as that observed in freshly isolated chromatin. Electron microscopic studies confirm the existence of reconstituted nucleosomes. Furthermore, the reconsti-mtion of nucleosomes from DNA and histones H2A, H2B, H3, and H4 is independent of the organismal or cellular origin of the various components. The histone HI and the nonhistone proteins are not necessary for the reconstitution of the nucleosome core. 

Most of the DNA of animal cells is found in the nucleus, where DNA is the major constituent of the chromosomes. On the other hand, most of the RNA is located in the cytoplasm. Nuclear DNA exists as a thin, double helix only 2 nm wide. The double helix is folded and complexed with protein to form chromosomal strands approxim-ately 100 to 200 nm in diameter. Each chromosome contains a single DNA duplex. The human chromosomes vary in size the smallest contains approximately 4.6 X 10 base pairs of DNA, and the largest 2.4 X 10 base pairs. In contrast, the Escherichia coli chromosome has 4.5 x 106 base pairs. The DNA of die chromosomes is tightly packed and associated with both histone and nonhistone proteins. 

The nucleus contains a large number of proteins other than histones. These so-called nonhistone proteins may or may not be tightly associated with the chromosomes. For example, the nucleus contains enzymes associated with the synthesis of RNA and DNA these are nonhistone proteins, but they are not part of the structure of chromosomes. One group of nonhistone proteins are the high mobility group (HMG) proteins, named for their rapid movement on polyacryl-amide gel electrophoresis. The HMG proteins, but not histone HI, are associated with the chromatin that is most active in RNA synthesis. 

Reeves, R., and Nissen, M.S. (1993) Interaction of high mobility group-I (Y) nonhistone proteins with nucleosome core particles./. Biol. Chem. 268, 21137-21146. 

While studying the binding of mercury by chromatin of rats injected with mercuric chloride, the nonhistone chromatin proteins in rat and kidney cell nuclei were shown to be mainly responsible for the mercury deposition [43]. The mercury-binding nonhistone proteins were found to be heterogeneous by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. 

Nickel sulphate in peripheral blood T lymphocytes gave a marked increase of 32P label into nonhistone proteins [ 109], especially in the 30-40 kDa region. It was postulated that the increase in nuclear protein phosphorylation probably reflected an activation of the lymphocytes. 

Chromatin The material of chromosomes. It is a complex of DNA, histones, and nonhistone proteins (chromosomal proteins, non-histone) found within the nucleus of a cell. [NIH]... 

Abstract Post-translational modifications of nonhistone proteins play a significant role in... 

Reversible acetylation of histone and nonhistone proteins play key role in maintaining cellular homeostasis. In this following section we shall discuss about the physiological significances of acetylation and deacetylation of different classes of nonhistone proteins. 

Figure 3. Role of nonhistone protein acetylation in maintaining cellular homeostasis- mis-regulation and disease connection (a) Acetylation of nonhistone proteins are associated with active or repressed chromatin architecture as guided by suitable cellular signals for maintenance of gene expression. Misreg-ulation of HAT function leads to diseased state, where chromatin architecture is altered than under normal condition. In a parallel way the posttranslational modification status of these proteins may act as versatile tool to diagnose the various stages of disease manifestation e.g. probable involvement of acetylated NPMl modulating its stress response function can lead us to use it as a marker for various disease states, (b) Acetylation of nonhistone proteins in connection to diseases like Cancer, AIDS, Diabetes and others. (See Colour Plate 14.)...

Glozak MA, Sengupta N, Zhang X, Seto E (2005) Acetylation and deacetylation of nonhistone proteins. Gene 363 15-23... 

Nuclear DNA in eukaryotes is found in chromatin associated with histones and nonhistone proteins. The basic packaging unit of chromatin is the nucleosome (Figure 1-1-13) ... 

Waga, S., Mizuno, S., and Yoshida, M. (1989) Nonhistone proteins HMGl and HMG2 suppress the nucleosome assembly at physiological ionic strength. Biochim. Biophys. Acta 1007, 209-214. 

Histone acetyltransferases (HATs) are enzymes that acetylate specific lysine residues in histones through the transfer of an acetyl group from an acetyl-coenzymeA (AcCoA) molecule, causing profound effects on chromatin structure and assembly as well as gene transcription. HATs are found in most, if not all, eukaryotic organisms as multiprotein complexes, some HAT catalytic subunits even being shared between various complexes that display different substrate specificities based on their subunit composition [12]. Despite their name, HATs do not restrict themselves to the acetylation of histones, since these enzymes have also been shown to act on nonhistone proteins, broadening their scope of action [13]. 

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