Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.31.1 (micrococcal nuclease)
2,818 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Chicken erythrocyte chromatins containing a single species of linker histone, H1 or H5, have been prepared, using reassembly techniques developed previously. The reconstituted complexes possess the conformation of native chicken erythrocyte chromatin, as judged by chemical and structural criteria; saturation is reached when two molecules of linker histone are bound per nucleosome, as in native erythrocyte chromatin, which the resulting material resembles in its appearance in the electron microscope and quantitatively in its linear condensation factor relative to free DNA. The periodicity of micrococcal nuclease-sensitive sites in the linker regions associated with histone H1 or H5 is 10.4 base pairs, suggesting that the spatial organization of the linker region in the higher-order structure of chromatin is similar to that in isolated nucleosomes. The susceptible sites are cut at differing frequencies, as previously found for the nucleosome cores, leading to a characteristic distribution of intensities in the digests. The scission frequency of sites in the linker DNA depends additionally on the identity of the linker histone, suggesting that the higher-order structure is subject to secondary modulation by the associated histones.
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PMID:Regulation of the higher-order structure of chromatin by histones H1 and H5. 728 11

The enzyme micrococcal nuclease was used to examine the accessibility of chromatin extracted from brains of 13 patients with senile and presenile dementia of the Alzheimer type. Compared with chromatin extracted from brains of 8 patients without neurological signs or brain pathology and brains of 7 patients with nonAlzheimer dementia, Alzheimer chromatin was less accessible to this enzyme. Reduced accessibility was reflected by a reduced yield of mononucleosomes in comparison with dinucleosomes and larger oligomers. Both neuronal and glial chromatin were found to be similarly affected. The reduced yield of mononucleosomes from Alzheimer chromatin is not due to their increased breakdown, but is probably related to protein associated with the internucleosomal linker region that retards nuclease action. Dinucleosomes isolated from control and Alzheimer nuclease digests were examined for their protein complement. Three perchloric acid-soluble proteins situated in the histone H1 region of sodium dodecyl sulfate (SDS) gels were present in elevated levels in Alzheimer dinucleosomes. These results represent the first example of altered chromosomal proteins associated with a diseased state of the brain.
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PMID:Changes in chromatin structure associated with Alzheimer's disease. 729 96

We have reported previously that five different electrophoretic forms of mononucleosomes (MI to MV) are produced upon treatment of mammalian chromatin with micrococcal nuclease. We show here that each of these mononucleosome classes possesses internal heterogeneity due to the presence of a variety of minor protein species. Defined subsets of mononucleosome classes MII to MV have been reconstituted by reassociating stripped nucleosomes with histone H1 and non-histone protein HMG-17. This procedure leads to the generation of the same five major electrophoretic forms of mononucleosomes found in native chromatin. From the results of one- and two-dimensional electrophoretic analyses on reconstituted samples, it is concluded that different mononucleosome classes possess the following subunit structures: MI, core histone octamer (8-mer); MII, 8-mer plus one copy of HMG-17; MIIIA, 8-mer plus one copy of histone H1; MIIIB, 8-mer plus two copies of HMG-17; MIV, 8-mer plus one copy each of histone H1 and HMG-17; and MV, 8-mer plus one copy of histone H1 and two copies of HMG-17. Equal numbers of HMG-14 molecules can substitute for HMG-17 and generate the same nucleosome components. Thus, mononucleosomes possess independent binding sites for at least 1 histone H1 molecule and 2 nonhistone chromosomal protein molecules. We show further that reassociated HMG-17 molecules can exhibit a rapid interchange between binding sites, even under conditions of low ionic strength.
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PMID:Subunit structures of different electrophoretic forms of nucleosomes. 736 65

DNA isolated from mammalian cell nuclear reveals discrete size patterns when partially digested with micrococcal nuclease. The DNA repeat lengths from different tissues within a species or from different species may vary. These differences have been attributed to the presence of different species of histone H1. To examine the nature of regulation of DNA repeat lengths and their possible relationship to histone H1, we have selected several mouse and human cell lines that differ in their DNA repeat lengths and examined them and their cell hybrids. 24 mouse X human and five mouse X mouse hybrid cell lines were analyzed. All the interspecific hybrids exhibited the repeat pattern characteristic of the murine parent. The mouse intraspecific hybrids had a repeat pattern of only one of the parents. We conclude that the partial human chromosome complements retained in the hybrids assume the repeat lengths exhibited by the mouse cells. Because H1 histones have been implicated in the determination of DNA repeat lengths, we also investigated the regulation of H1 histone expression in these cell hybrids. Purified H1 histones were radioactively labeled in vitro, and individual subfractions were subjected to proteolysis followed by gel electrophoresis. The resulting partial peptide maps off H1 histone subfractions A and B were distinguishable from one another and from different cell lines. In the mouse X human hybrids analyzed, only the mouse H1 histones were detected. These observations were extended to H2b by analysis of the hybrid cell histone by Triton-acid-urea gels. Neither the DNA repeat length nor histone expression is affected by the presence of any specific human chromosome. The fact that human genes are expressed in these hybrids suggests that the H1 histones of one species is able to interact with the chromatin of another species in a biologically funtional conformation. Analysis of the intraspecific PG19 X B82 (mouse X mouse) hybrids reveals the presence of H1 histone subfractions of the B82 mouse cells. Because these hybrids exhibit the nucleosome repeat length only of the PG19 cells, it appears that if histone H1 plays a role in determining the repeat length it does so in consort with other nonhistone chromosomal proteins.
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PMID:Histone gene expression and chromatin structure in mammalian cell hybrids. 741 91

Poly(ADP-ribose) [poly(ADP-Rib)] polymerase of HeLa nucleosomes has been shown in vitro, to catalyze the synthesis of a complex of histone H1 containing 2 H1 histones and 15-16 units of oligo(ADP-Rib). The synthesis of the H1 complex in vitro was compared in polynucleosome populations of various sizes (3--16 and greater than 30) released from HeLa nuclei following micrococcal nuclease digestion. Poly(ADP-Rib) was synthesized from [32P]NAD and the poly(ADP-ribosyl)ation of H1 was studied by selective H1 extraction, gel electrophoresis and autoradiography. Quantitative differences in H1 complex formation occurred when either chromatin concentration or polynucleosome length was varied. The data indicated that H1 complex formation in vitro was favored in polynucleosomes 16 nucleosomes long as compared to 8 nucleosomes. A series of partially ADP-ribosylated H1 species was also detected. Partially modified H1 species migrate more slowly than pure H1 in dodecylsulfate gels. The reduced mobility is a function of the number of attached ADP-Rib moieties. Thus, molecules containing one molecule of H1 and various numbers of ADP-Rib residues can be separated. When the partially modified H1 species were incubated in alkali to cleave the linkage of ADP-Rib to protein, (ADP-Rib1-15) were detected by chain length analysis on 15% polyacrylamide gels. The intermediate H1 species could be chased, in vitro, into as H1 complex with NAD and thus were determined to be successive precursors in the formation of the H1 complex. Evidence is presented that the H1 complex is synthesized in intact cells permeabilized with lysolecithin.
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PMID:Characterization of poly(ADP-ribose)--histone H1 complex formation in purified polynucleosomes and chromatin. 746 Sep 42

We have examined the gel profiles of staphylococcal nuclease digests of intact nuclei following different extents of removal of histone H1 by low pH. It was found that the submonomer fragment pattern (i.e. fragments less than 140 base pairs (bp) changed dramatically following removal of H1. The most striking feature of this change was a marked increase in the relative intensity of a band migrating at 102 +/- 4 bp when about 20-50% of the nuclear DNA is rendered acid soluble. All other submonomer bands decreased in relative intensity. There was no evidence for an approximately 100-bp repeat pattern accompanying the enhanced generation of the 102-bp fragment following H1 removal. This result, along with the comparisons of gel profiles for different extents of digestion, suggests that removal of histone H1 from nuclei results in an increased susceptibility of the DNA to staphylococcal nuclease at one or both ends of many of the core particles and that a strong block to further digestion occurs within these core particles resulting in the formation of a relatively stable 102-bp fragment.
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PMID:Removal of histone H1 from intact nuclei alters the digestion of nucleosome core DNA by staphylococcal nuclease. 746 51

The chromatin structure of morphologically-similar, but increasingly-malignant erythroleukemia cells was investigated using milk micrococcal nuclease digestion of isolated nuclei. The maximum solubilization of chromatin was unique for each of the three cell types: the least malignant (our Stage II) released 61% of its chromatin DNA, the most malignant (Stage IV), 46%, and the intermediate (Stage III) released 36%. An analysis of the nucleosome oligomers liberated by digestion also demonstrated differences. After 15 minutes of digestion when release was reaching its maximum, a greater proportion of large nucleosomal oligomers (sizes > trinucleosome) was released from Stage II nuclei than from Stage III or IV nuclei. The cell types also differed in the relative amount of H1-depleted mononucleosomes released. Analysis of the size of the double-stranded DNA associated with mononucleosomal particles showed that Stage III mononucleosomes were smaller (148 bp) than Stage IV (167 bp) or Stage II (190 bp). In addition, while the DNA of mononucleosomes depleted in H1 was smaller than that in the H1-containing species, relative size differences among the different cell types were retained. These data suggested that the difference in the mononuocleosome particle size resistant to nuclease digestion was independent of histone H1. Differences in nucleosome repeat length were also noted among the cell types. These studies have demonstrated dramatic differences in chromatin structure associated with malignant potential of an otherwise morphologically identical cell type. These findings may reflect changes in the relative amounts of H2a variants which we have previously described among the different malignant cell types.
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PMID:Organizational changes in chromatin at different malignant stages of Friend erythroleukemia. 746 15

Stepwise addition of polyanions (PA)-heparin and dextran sulfate-to interphase rat liver nuclei results in increased chromatin condensation (PA/DNA = 0.125) followed by its decondensation down to 10 nm fibrils (PA/DNA = 0.2) and, eventually, (PA/DNA > 0.3) to a new condensation of the material up to 30-50 nm fibrils and 0.15-0.5 M compact globular particles (GP). After subsequent addition of ammonium acetate (0.15-0.5 M) the whole nuclear material converts into an even network of GP connected by fibrils containing DNA. The GP diameter (40-70 nm) is unaffected in the PA/DNA range of 0.4 to 1.5. The GP-containing nuclei retain up to 85-90% of DNA and 50-70% of the protein. Treatment of the nuclei with staphylococcal nuclease reveals the absence of nucleosomal periodicity in the DNA structure. The nuclei treated with PA and the salt in the presence of EDTA retain all the histones of the nucleosomal core. When treated in the presence of Mg2+, the nuclei retain also histone H1. The GP obtained at pH 6.0-6.5 are the most compact ones. At pH 5.0 and 8.5 GP partly form tangles of approximately 10 nm granules linked by thin fibrils. GP can be reversibly unfolded into the same fibro-granular network when dyalized against low ionic strength solutions in the presence of EDTA. A more than 1.5-fold increase in the PA/DNA ratio or treatment of GP-containing nuclei with nucleases terminate in the failure of the fibrillar network between GP, giving rise to large globules (> 300 nm), presumably at the expense of GP fusion. In this case the nuclei lose DNA but retain no less than 70% of histones. The diameter of large globules depends on the concentration of PA. GP are suggested to arise by the aggregation of PA complexes with histone cores of nucleosomes and with other alkaline proteins of chromatin at the regularly spaced sites of partly deproteinated chromatin.
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PMID:[Effect of polyanions on the structure of rat liver nuclear chromatin]. 765 65

The activated c-Ha-rasVal12 oncogene is often involved in the genesis of human malignancies. We show here that in c-Ha-rasVal12 oncogene-transformed mouse NIH 3T3 fibroblasts the copy number and expression level of the mutant ras oncogene correlates with the degree of chromatin decondensation, as assessed by micrococcal nuclease (MNase) and DNase I digestion. MNase and DNase I analyses further revealed that the nucleosomal repeat lengths were different in the normal and ras oncogene-transformed cells, 162.3 bp and 178.1 bp, respectively. These chromatin changes were accompanied by alterations in the content of histone H1 zero. Furthermore, using DNase I as a probe, we discovered that serum stimulation of normal and transformed cells, synchronized by serum starvation, induces rapid reversible changes in the structure of bulk chromatin that may be linked to transcriptional activation. Our data thus indicate that cell transformation by ras is associated with specific changes in chromatin structure that make it more vulnerable, and prone to additional mutations characteristic of cancer development in vivo.
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PMID:Cell transformation by c-Ha-rasVal12 oncogene is accompanied by a decrease in histone H1 zero and an increase in nucleosomal repeat length. 772 50

Soluble chromatin was prepared from rat testes after a brief micrococcal nuclease digestion. After adsorption onto hydroxylapatite at low ionic strength, the histone H1 subtypes were eluted with a shallow salt gradient of 0.3 M NaCl to 0.7 M NaCl. Histone H1t was eluted at 0.4 M NaCl, while histones H1a and H1c were eluted at 0.43 M NaCl and 0.45 M respectively. The extreme divergence of the amino acid sequence of the C-terminal half of histone H1t, the major DNA binding domain of histone H1, from that of the somatic consensus sequence may contribute to the weaker interaction of histone H1t with the rat testis chromatin. Further, histone H1t was not phosphorylated in vivo in contrast to histone H1a and H1c, as is evident from the observation that histone H1t lacks the SPKK motif recognized by the CDC-2kinase or the RR/KXS motif recognized by protein kinase A.
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PMID:Testis-specific histone (H1t) is not phosphorylated and has a weak interaction with chromatin. 800 17


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