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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)

Chromatin was solubilized from rat liver nuclei by digestion with the restriction nuclease EcoRI or HaeIII in the presence or absence of EDTA and sodium chloride. The samples were investigated by electron microscopy after positive and negative staining with uranyl acetate under a number of conditions. Depending on the salt concentration during solubilization the chromatin appeared as beads on the string or in more compact form. Solenoid- and superbead-like structures were seen as had been reported for chromatin solubilized with micrococcal nuclease.
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PMID:Characterization of restriction nuclease prepared chromatin by electron microscopy. 10 62

Nuclei and chromatin from trout testis cells were digested with three different nucleases (DNase I, DNase II, and micrococcal nuclease), and the acid-soluble proteins that were solubilized and those remaining bound to the nuclease-resistant DNA were compared electrophoretically. With the conditions described by H. Weintraub and M Groudine [(1976) science, 193, 848-856], which we previously found to be selective in digesting actively transcribed regions in trout testis chromatin, a single chromosomal protein, H6, was solubilized. The nucleosomal histones and H1 remained insoluble, bound to the resistant DNA. In contrast, digestion with micrococcal nuclease led to a preferential solubilization of a second protein, HMG-T, together with the release of some nucleosomal histones and H1 into the soluble fraction. DNase II also discriminated between "active" and "inactive" chromatins; when a DNase II-solubilized "active" chromatin fraction was prepared, it too was enriched in H6 and HMG-T. Thus, both H6 and HMG-T, the two major low-salt extractable chromosomal nonhistone the two major low-salt extractable chromosomal nonhistone proteins from trout testis, are associated with chromatin regions selectively sensitive to nucleases. The preferential solubilization of HMG-T by micrococcal nuclease action suggests that it might be located at the internucleosomal "spacer" region.
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PMID:Selective association of the trout-specific H6 protein with chromatin regions susceptible to DNase I and DNase II: possible location of HMG-T in the spacer region between core nucleosomes. 26 31

In optimizing previously reported coagulase agar media to obtain a rapid, reliable, and inexpensive coagulase test agar, variations in plasmas, pH, buffer system, fibrinogen, and fibrinolytic inhibitor were investigated. The agar with the following composition was determined best for the demonstration of coagulase production by Staphylococcus aureus: 25 ml of 15% bovine fibrinogen (fraction I, type I, citrated, Sigma Chemical Co.), 25 ml of rehydrated rabbit plasma (coagulase plasma ethylenediaminetetraacetic acid, Difco), 10.0 mg of soybean trypsin inhibitor (Schwarz/Mann), and 450 ml of brain heart infusion agar (Difco). In additional studies involving 7 different temperatures and 11 heating times, the thermal destruction of microbial nucleases on plate count agar and coagulase test agar was investigated. Heating the plates for 2.5 h at 65 degrees C destroyed all heatlabile nucleases, but not thermonucleases of S. aureus. A tandem agar plate method for the identification of S. aureus was developed. Coagulase and thermonuclease activity of 50 colonies can be detected on a single agar plate. Suspect S. aureus colonies isolated on various selective media are transferred to coagulase test agar, the plates are incubated at 37 degrees C for 18 h, and the coagulase reaction is recorded. The plates are then heated at 65 degrees C for 2.5 h, overlaid with toluidine blue-metachromatic diffusion agar, and reincubated at 37 degrees C for 3 h, and the thermonuclease reaction is recorded. Studies based on 88 enterotoxigenic S. aureus strains and 133 and 48 suspect S. aureus strains isolated from fresh salami mixtures on mannitol salt and tellurite-polymyxin-egg yolk agars, respectively, demonstrated 100% agreement between the tandem agar plate method and standard coagulase and thermonuclease tests. Overall, the tandem agar plate method is a rapid and convenient approach contributing to the identification of S. aureus from foods.
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PMID:Tandem coagulase/thermonuclease agar method for the detection of Staphylococcus aureus. 37 27

The ability of high molecular weight chicken erythrocyte chromatin to spontaneously self-assemble into native-like material, after dissociation by high ionic strength and reassociation by salt gradient dialysis, was critically examined. The native conformational state of the reassembled nucleoprotein complex was regenerated to the extent reflected by circular dichroism spectra and thermally induced helix--coil transition of the nucleoprotein DNA. However, internucleosomal packing of approximately 205 base pairs of DNA per repeating unit, as probed by digestion with micrococcal nuclease, was not regenerated upon reassembly and was replaced by a packing of approximately 160 base pairs per repeating unit. Thus, high molecular weight chromatin containing only lysine-rich histones (H1 and H5) and core histones (H2A, H2B, H3, and H4) is not a true self-assembling system in vitro using the salt gradient dialysis system used herein. Circular dichroism and thermal denaturation studies on core chromatin (lysine-rich histones removed) showed that core histones alone are not capable of reassembling high molecular weight DNA into native-like core particles at low temperature (4 degree C). Reassembly at 21 degree C restored the circular dichroism but not the thermal denaturation properties to those characteristic of undissociated core chromatin. Nonetheless, micrococcal nuclease digestions of both reassembled core chromatin products were identical with undissociated native core chromatin. Ressembly in the presence of the complete complement of histones, followed by removal of the lysine-rich histones, did regenerate the thermal denaturation properties of undissociated native core particles. These results indicated multiple functions of the lysine-rich histones in the in vitro assembly of high molecular weight chromatin.
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PMID:Analysis of chromatin reconstitutiion. 42 Aug 8

Extracts of human lymphoblastoid cells catalyzed complete release of uracil (Ura) from PBS1 DNA, which contains Ura instead of thymine as a normal component (Ura-DNA), and 3-methyladenine (3-MeAde) from DNA methylated with methyl methanesulfonate (Me-DNA). These two activities, Ura-DNA glycosylase and 3-MeAde-DNA glycosylase, differed in heat stability. Cell extracts released Ura more rapidly and 3-MeAde more slowly from alkali-denatured preparations of Ura- and Me-DNA, respectively, than from native DNA's. On incubation with reconstituted chromatins, prepared from Ura-DNA and Me-DNA, respectively, with calf thymus chromosomal protein by salt gradient dialysis, cell extracts released all the Ura but only about half of the 3-MeAde residues, although both these chromatins were degraded by micrococcal nuclease until about half of the nucleotides became acid soluble. The activities of Ura-DNA and 3-MeAde-DNA glycosylase of xeroderma pigmentosum cells were similar to those of normal cells.
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PMID:Actions of human DNA glycosylases on uracil-containing DNA, methylated DNA and their reconstituted chromatins. 46 95

A small proportion (0.1-0.5%) of the total DNA content of native Chinese hamster metaphase chromosomes is protected from nucleolytic degradation following the removal of histones by extraction with either 0.2 N HCl or 2 M NaCl, and remains attached to the nonhistone protein core. Acid extraction followed by DNase I digestion leads to small fragments of 10-30 bases. Salt extraction followed by micrococcal nuclease digestion gives approx. 140 b.p. fragments which are undistinguishable in size from nucleosome core DNA fragments. Furthermore, DNase I treatment of salt extracted chromosomes gives DNA fragments containing single strands which are multiples of 10 bases in length, again characteristic of the nucleosome structure. Reassociation kinetics using the 32P-labelled 140 b.p. fragments as probes suggests they are enriched for rapidly reassociating sequences.
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PMID:A partial characterization of DNA fragments protected from nuclease degradation in histone depleted metaphase chromosomes of the Chinese hamster. 49 44

Histone proximity in chromatin was studied with the cleavable crosslinking reagent, dithiobissuccinimidyl propionate. Crosslinks between H4 and H2a, H4 and H2b, H4 and H3, H2a and H2b, H2b and H3 were found. H1 is also crosslinked to the nucleosomal histones. In nuclei, unsheared chromatin, and H1 depleted chromatin, the four nucleosomal histones are crosslinked at similar relative rates both in 5 mM salt and 100 mM salt. After micrococcal nuclease treatment to generate nucleosomes, H2a and H2b are crosslinked faster than H4 and H3. C14-NEM titration of thiopropionate residues bound to each histone shows that H2a and H2b are more accessible to this reagent after nuclease treatment but that the increased binding was not sufficient by itself to explain the increase in crosslinking. Bolton Hunter reagent was used to further study the accessibility of the four nucleosomal histones in whole chromatin and nuclease digested chromatin. These studies showed that salt increases the accessibility of all four histones while nuclease treatment decreases H4 accessibility.
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PMID:Proximity and accessibility studies of histones in nuclei and free nucleosomes. 64 11

The endogenous nucleolytic reaction occurring in rabbit thymus nuclear lysates has been studied at extended incubation times (up to 4 h). Production of nucleosomal polymers containing multiples of 205 base pairs of DNA was observed. The stability of the bands and the low release (1%) of acid-soluble nucleotides indicated there was only a small fraction of sensitive DNA between the subunits. The salt-soluble chromatin formed in the endogenous reaction at short incubation times (14--24 min) and purified over Sephadex G-200 has been treated with micrococcal nuclease and DNAase I. With micrococcal nuclease, nucleosomal polymers containing multiples of 201 base pairs of DNA were formed. Extensive digestion reaveled a core subunit containing 145 base pairs of DNA. With DNAase I only random degradation was observed and nucleosomal complexes were not produced.
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PMID:A study of an endogenous nucleolytic reaction and of the action micrococcal nuclease and DNAase I on a salt-soluble, compact form of chromatin. 70 40

n-Butyrate treatment of growing Hela cells produces a dramatic increase in the levels of histone acetylation. We have exploited this system to study the effect of histone acetylation on chromatin structure. Chromatin containing highly acetylated histones is more rapidly digested to acid-soluble material by DNase I, but not by micrococcal nuclease. The same pattern of nuclease sensitivity was exhibited by in vitro-assembled chromatin consisting of SV40 DNA Form I and the 2 M salt-extracted core histones from butyrate-treated cells. Using this very defined system, it was possible to demonstrate that acetylated nucleosomes do not have a greatly diminished stability. Stability was measured in terms of exhange of histone cores onto competing naked DNA or sliding of histone cores along ligated naked DNA. Finally, it was shown that acetylated nucleosomes are efficient inhibitors of in vitro RNA synthesis by the E. coli holoenzyme as well as by the mammalian polymerases A and B.
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PMID:Effect of histone acetylation on structure and in vitro transcription of chromatin. 72 94

Chromatin core particles, containing 140 base pairs (bp) of DNA plus the inner histones, can be nearly quantitatively formed either by reassociation from 2 M NaCl or by reconstitution from salt extracted histones and DNA. The reassociated or reconstituted particles appear to be identical with the native particles in all physical properties examined (sedimentation velocity, histone content, circular dichroism, and melting) as well as in their patterns of digestion by micrococcal nuclease, DNase I, and trypsin. In the presence of excess DNA, no "half-particles" are formed. In the presence of excess histone, aggregated structures are formed in addition to 11S core particles.
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PMID:Reconstitution of chromatin core particles. 92 32


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