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

---

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

Micrococcal nuclease digestion of chromatin from growing cells reveals a structural organization which differs for genes transcribed at diverse rates. The late cAMP dependent prespore genes which are not transcribed in growing cells are found in growing cells in a regular nucleosomal repeat with an average spacing of 168 nucleotides. By contrast genes expressed at a low level in growing cells show an irregular pattern of bands with an average distance between bands of 80 nucleotides. The sizes of the bands generated from the transcribed genes are consistent with the concept that transcription results in the loss of the linker region histone H1 with concomitant sliding of nucleosomes to generate close packed ("slipped") di, tri, and tetra nucleosomes lacking the linker region. Further analysis of dinucleosomes released by micrococcal nuclease digestion reveals that transcriptionally active genes are found associated with dinucleosomes species which may be lacking histone H1. The length of DNA protected by these dinucleosomes is heterogeneous, ranging from 250 to 300 nucleotides. Methodology is described which has been adapted to allow two dimensional hybridization mapping of nucleoprotein complexes on single copy Dictyostelium genes.
...
PMID:Gene expression and chromatin structure in the cellular slime mold, Dictyostelium discoideum. 164 96

The subnucleosomal organization of Tetrahymena chromatin, which has an unusual H1 histone, was investigated by NaCl extraction and micrococcal nuclease digestion of nuclei. It was found that Tetrahymena histone H1 is extracted with 0.35 M NaCl, whereas bovine thyroid H1 is not. Micrococcal nuclease digestion of Tetrahymena nuclei did not yield chromatosomes as a stable intermediate, whereas digestion of bovine thyroid nuclei did.
...
PMID:Chromatosomes are not produced from Tetrahymena chromatin by micrococcal nuclease digestion. 190 Feb 45

Assembly of nucleosomes on relaxed, covalently closed DNA has been studied in a nuclear extract of Xenopus laevis oocytes. Nucleosomes containing the four histones H3, H4, H2A and H2B but lacking histone H1 are readily assembled on the DNA. The pattern of micrococcal nuclease digestion shows that the nucleosomes assembled in the absence of ATP and Mg (II) are closely packed, with a periodicity of 150 base pairs (bp). In contrast, in the presence of ATP and Mg (II) the spacing of the nucleosomes is 180 bp, similar to that observed for nucleosomes assembled on DNA microinjected into oocyte nuclei. The ATP and Mg (II) requirements for the assembly of correctly spaced nucleosomes are unrelated to the activity of the ATP and Mg (II) dependent DNA topoisomerase II in the extract; addition of specific inhibitors of eukaryotic DNA topoisomerase II has no effect on the spacing of the reconstituted nucleosomes. The ATP requirement in the assembly of correctly spaced nucleosomes can be substituted by adenosine 5'-O-3'-thiotriphosphate (gamma-S-ATP) but not by adenyl-5'-yl imidodiphosphate (AMP-P-(NH)-P).
...
PMID:Assembly of correctly spaced chromatin in a nuclear extract from Xenopus laevis oocytes. 217 Sep 36

Flow cytometric assessment of DNA digestion with micrococcal nuclease has been performed on isolated HeLa nuclei by determining the relative reduction in stainability with the DNA-specific fluorochrome, propidium iodide. At the nuclease concentrations used, DNA histograms of digested nuclei showed the typical bimodal pattern, when the enzymatic reaction was performed in a medium maintaining chromatin in its native (i.e. condensed) or partially decondensed from. In contrast, when nuclei were digested in a buffer lacking both the mono- and divalent cations K+ and Mg2+, an extensive decrease in fluorescence intensity, with loss of the histogram shape, was observed. In nuclei with native chromatin, DNA stainability decreased as a function of time and enzyme concentration, to reach a lower limit of about 46%, as compared with undigested control samples. Removal of the histone H1 induced a significant increase (approximately by a factor of 2) in the extent of digestion, although only in nuclei with partially decondensed chromatin. These results suggest that the sensitivity of DNA to digestion with micrococcal nuclease can be quantitatively monitored with flow cytometry when appropriate reaction conditions are chosen.
...
PMID:Flow cytometric evaluation of DNA digestion with micrococcal nuclease on isolated HeLa nuclei. 224 61

We have compared the mononucleosomal pattern produced by micrococcal nuclease digestion of condensed and unfolded chromatin and chromatin in nuclei from various sources with the repeat length varying from 165 to 240 base-pairs (bp). Upon digestion of isolated H1-containing chromatin of every tested type in a low ionic strength solution (unfolded chromatin), a standard series of mononucleosomes (MN) was formed: the core particle, MN145, and H1-containing, MN165, MN175, MN185, MN195, MN205 and MN215 (the indexes give an approximate length of the nucleosomal DNA that differs in these particles by an integral number of 10 bp). In addition to the pattern of unfolded chromatin, digestion of whole nuclei or condensed chromatin (high ionic strength of Ca2+) gave rise to nuclei-specific, H1-lacking MN155. Digestion of H1-lacking chromatin produced only MN145, MN155 and MN165 particles, indicating that the histone octamer can organize up to 165 bp of nucleosomal DNA. Although digestion of isolated sea urchin sperm chromatin (repeat length of about 240 bp) at a low ionic strength gave a typical "unfolded chromatin pattern", digests of spermal nuclei contained primarily MN145, MN155, MN235 and MN245 particles. A linear arrangement of histones along DNA (primary organization) of the core particle was found to be preserved in the mononucleosomes, with the spacer DNA length from 10 to 90 bp on one (in MN155) or both sides of core DNA being a multiple of about 10 bp. In MN235, the core particle occupies preferentially a central position with the length of the spacer DNA on both sides of the core DNA being usually about 30 + 60 or 40 + 50 bp. Histone H1 is localized at the ends of these particles, i.e. close to the centre of the spacer DNA. The finding that globular part of histones H3 and sea urchin sperm H2B can covalently bind to spacer DNA suggests their involvement in the organization of chromatin superstructure. Our data indicate that decondensation of chromatin is accompanied by rearrangement of histone H1 on the spacer DNA sites adjacent to the core particle and thus support a solenoid model for the chromatin superstructure in nuclei in which the core DNA together with the spacer DNA form a continuous superhelix.
...
PMID:Structure of nucleosomes and organization of internucleosomal DNA in chromatin. 232 31

Chromatin fractions from Friend erythroleukemia cells after induction of differentiation by dimethylsulfoxide (DMSO) were compared in their biochemical characteristics to fractions from uninduced cells. Fractions were prepared by extracting chromatin from nuclei after mild micrococcal nuclease treatment with increasing concentrations of NaCl according to Sanders. This procedure has been found to release chromatin containing hyperacetylated histones preferentially. The fractions obtained by this procedure were analysed in respect to the amount of chromatin released, the amount of histone H1, the degree of acetylation of histone H4, the presence of non-histone proteins and the concentration of transcribed and non-transcribed sequences. It was found that the fractions differ in the amount of histone H1 present, in several non-histone proteins and in the acetylation of histone H4, regardless whether induced or uninduced cells were analysed. The distribution of transcribed sequences versus non-transcribed sequences among the fractions was the same, demonstrating that this fractionation procedure, although leading to fractions with biochemical differences, is not able to discriminate functional states of chromatin and that the biochemical characteristics of the fractions may be common to both, active as well as inactive states of chromatin.
...
PMID:Biochemical characterization of chromatin fractions isolated from induced and uninduced Friend erythroleukemia cells. 257 Oct 75

We have developed a competitive enzyme-linked immunosorbent assay for solubilized kinetochore components, using human CREST (calcinosis, Raynaud's phenomenon, esophageal dysfunction, sclerodactyly, telangiectasia) scleroderma autoimmune antibodies specific for these kinetochore elements. Using this quantitative assay, we found interphase persistent or "pre-kinetochore" components in low- and moderately high-salt (375 mM salt) extracts of micrococcal nuclease-digested rat liver and chicken erythrocyte nuclei. The release of antigen activity from nuclei under these conditions has been correlated with loss of pre-kinetochore foci as determined by immunofluorescence microscopy. Combined biochemical and competition assay analysis of chicken erythrocyte nuclear extracts indicates that pre-kinetochore components are tightly bound to chromatin of mononucleosome size. The conclusions based on competition assay data are supported by a direct binding assay, which confirms that antigens recognized by CREST sera are present on chromatin. These results raise the possibility that the kinetochore-specific chromosomal antigen(s) we have detected substitutes for "standard" mononucleosome components, such as histone H1. Furthermore, they suggest approaches to the isolation of kinetochore-specific DNA sequences from higher eucaryotes.
...
PMID:Kinetochore components recognized by human autoantibodies are present on mononucleosomes. 258 Feb 29

Digestion of nuclear chromatin of Trypanosoma brucei brucei procyclic culture forms with micrococcal nuclease yielded DNA fragments which formed DNA ladders in agarose gels, similar to those of rat liver. However, the chromatin of trypanosomes was digested more rapidly. The digestion of T. b. brucei chromatin yielded a large amount of DNA fragments of core-particle size. The numbers of base pairs per nucleosomal and linker DNA were identical in both species, if the digestion conditions were reduced in the case of T. b. brucei. Psoralen cross-linking of soluble chromatin of trypanosomes at 5 mM salt at pH 7 or pH 10 resulted in an irregular array of single-stranded (ss) bubbles separated by variable stretches of double-stranded (ds) DNA. The proportion of ss DNA was low compared with the ratio of ss/ds stretches in rat liver chromatin, which also showed regularly arranged nucleosomal DNA. Soluble chromatin of T. b. brucei, pre-treated with 500 mM NaCl to remove a potential H1 and psoralen cross-linked at 5 mM salt at pH 7 or pH 10 was to a great extent ds in both situations. The true nucleosome filament organization of T. b. brucei chromatin could only be shown by psoralen cross-linking the DNA in whole nuclei under physiological conditions. The results indicate that the chromatin of procyclic T. b. brucei differs significantly in its compaction pattern from rat liver chromatin; a typical histone H1 is not found, and the DNA-protein interactions are also less stable and can more easily be destabilized by experimental conditions.
...
PMID:Instability of the nuclear chromatin of procyclic Trypanosoma brucei brucei. 260 98

The granular particles of chromatin peripheral layer, were isolated together, with the nuclear envelope by treatment of nuclei with nuclease. These particles differ from total chromatin by a decreased content of histone H1, a specific set of minor acid-soluble proteins and a low DNA methylation level. Taking account of the fact that these particles facilitate chromatin interaction with the nuclear envelope, the latter were termed as "anchorosomes". Using UV-induced cross-linking of DNA to the proteins, it was found that all anchorosome-specific acid-soluble proteins can directly interact with anchorosomal DNA. Treatment of anchorosomes with staphylococcal nuclease and electron microscopic data showed that anchorosomes have a nucleosomal organization. Five to ten per cent of anchorosomal DNA appear to be firmly bound to nuclear lamina. This DNA cannot be separated from the lamina by treatment with 2 M NaCl, 1% SDS or heparin (1 mg/ml). The bulk of DNA in the laminal fraction after treatment with the above reagents is protected from hydrolysis with DNAase I by anchorosomal proteins and thus has a high molecular weight (10,000-30,000 base pairs). After treatment of anchorosomes with 0.6 M or 2 M NaCl, DNAase I splits this DNA, predominantly to minor fragments.
...
PMID:[Study of peripheral chromatin granules--anchorosomes]. 262 53

The Xenopus oocyte supernatant (oocyte S-150) forms chromatin in a reaction that is affected by temperature and by the concentration of ATP and Mg. Under optimal conditions at 27 degrees C, relaxed DNA plasmids are efficiently assembled into supercoiled minichromosomes with the endogenous histones H3, H4, H2A and H2B. This assembly reaction is a gradual process that takes four to six hours for completion. Micrococcal nuclease digestions of the chromatin assembled under these conditions generate an extended series of DNA fragments that are, on average, multiples of 180 base-pairs. We have examined the effect of histone H1 in this system. Exogenous histone H1, when added at a molar ratio of H1 to nucleosome of 1:1 to 5:1, causes an increase in the micrococcal nuclease resistance of the chromatin without causing chromatin aggregation under these experimental conditions. Furthermore, the periodically arranged nucleosomes display longer internucleosome distances, and the average length of the nucleosome repeat is a function of the amount of histone H1 added, when this histone is present at the onset of the assembly process. In contrast, no major change in the length of the nucleosome repeat is observed when histone H1 is added at the end of the chromatin assembly process. Protein analyses of the purified minichromosomes show that histone H1 is incorporated in the chromatin that is assembled in the S-150 supplemented with histone H1. The amount of histone H1 bound to chromatin is a function of the total amount of histone H1 added. We define here the parameters that generate histone H1-containing chromatin with native nucleosome repeats from 160 to 220 base-pairs, and we discuss the implications of these studies.
...
PMID:Assembly and properties of chromatin containing histone H1. 281 Mar 66


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---