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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)

Metaphase chromosomes prepared from colcemid-treated mouse L929 cells by non-ionic detergent lysis exhibit distinct heterochromatic centromere regions and associated kinetochores when viewed by whole mount electron microscopy. Deoxyribonuclease I treatment of these chromosomes results in the preferential digestion of the chromosomal arms leaving the centromeric heterochromatin and kinetochores apparently intact. Enrichment in centromere material after DNase I digestion was quantitated by examining the increase in 10,000 X g pellets of the 1.691 g/cc satellite DNA relative to main band DNA. This satellite species has been localized at the centromeres of mouse chromosomes by in situ hybridization. From our analysis it was determined that DNase I digestion results in a five to six-fold increase in centromeric material. In contrast to the effect of DNase I, micrococcal nuclease was found to be less selective in its action. Digestion with this enzyme solubilized both chromosome arms and centromeres leaving only a small amount of chromatin and intact kinetochores.
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PMID:Selective digestion of mouse metaphase chromosomes. 64 80

High mobility group (HMG) proteins from fetal calf thymus and mouse brain chromatin were purified and compared electrophoretically. The four major HMG proteins characteristic of fetal calf thymus chromatin (HMG's 1, 2, 14, and 17) were also found to be present in mouse brain chromatin. Nuclei from these two eucaryotic tissues were digested with DNase I and micrococcal nuclease and the acid-soluble proteins solubilized by the two nucleases in both tissues were analyzed on starch gels. Limited digestion of fetal calf thymus nuclei with DNase I led to the solubilization of a substantial fraction of proteins HMG-1 and HMG-2 together with smaller amounts of H1. In addition, limited digestion with micrococcal nuclease released approximately 70% of HMG's 1 and 2 and variable amount of H1 into the soluble fraction. The observation that HMG proteins 1 and 2 are selectively solubilized under conditions in which active genes have been shown to be preferentially digested in various other cell types suggests their selective association with chromatin regions which are transcriptionally competent.
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PMID:A study of the localization of high mobility group proteins in chromatin. 66 94

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

Digestion of fixed metaphase chromosomes by endonucleases (micrococcal nuclease and DNase II) under optimal digestion conditions followed by Giemsa staining produces sharp banding patterns identical to G-bands. In 3H-thymidine labeled, synchronized metaphase cells of the chinese hamster (CHO line), the band induction is accompanied by the removal of DNA. The single strand specific nuclease S1 and DNase I do not produce such banding patterns.
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PMID:Responses of mammalian metaphase chromosomes to endonuclease digestion. 74 3

Native chromatin and chromatin subunits (nucleosomes) were titrated with polylysine and digested with micrococcal nuclease and deoxyribonuclease I at individual lysine/nucleotide ratios. In contrast to earlier reports, which had been obtained using mechanically sheared chromatin, a comparison of the sites accessible for micrococcal nuclease and polylysine reveals that polylysine does not preferentially protect the micrococcal-nuclease-susceptible sites in chromatin. Similar results were obtained in digestion experiments with DNase I. From the experimental data presented we conclude that polylysine does not preferentially bind to the internucleosomal DNA, which is the prime target site for micrococcal nuclease, but rather to the total nucleosomal DNA moiety.
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PMID:Binding of polylysine to chromatin subunits and cleavage by micrococcal nuclease. A comparison of accessible sites. 89 21

Chromatin 'core particles' have been digested with trypsin to varying extents. The resulting particles are homogeneous by the criterion of ultracentrifuge boundary analysis. Sedimentation coefficients are lowered as cleavages are introduced into the histones, showing that an unfolding of the core particle occurs. This unfolding is further characterised by a lower melting temperature together with a premelting phase, higher molar ellipticity in the circular dichroism spectra at 280 nm and increased kinetics of digestion by both micrococcal nuclease and DNase I. Differences are also observed in the products of nuclease digestion. The most consistent interpretation of the data involves an unfolding process whereby free rods of DNA are released to extend from a nucleoprotein core.
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PMID:Chromatin core particle unfolding induced by tryptic cleavage of histones. 89 84

The chromatin of the lepidopteran Ephestia kuehniella was digested by micrococcal nuclease, DNase I and S1-nuclease combined with DNase I pretreatment. The resulting DNA fragments were analyzed by gel electrophoresis and compared with the DNA fragments of rat liver nuclei obtained by the same process. Extensive homology was revealed between insect and mammalian chromatin structure. The combined DNase I- S1-nuclease digestion yields double-stranded DNA fragments of lengths from 30 to 110 base-pairs. These DNA fragments are not obtained from nuclei predigested extensively with micrococcal nuclease. The results are discussed with respect to the internal structure of the chromatin subunit.
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PMID:Digestion of insect chromatin with micrococcal nuclease, DNase I and DNase I combined with single-strand specific nuclease S1. 90 68

The proportion of cytosines methylated in the DNA of nucleosome oligomers and of core particles appears indistinguishable from that of total nuclear DNA from CHO cells. However the DNA in nucleoprotein which is initially released from nuclei by treatment with very low levels of micrococcal nuclease and the first 10% of material rendered acid soluble by treatment of nuclei with DNase I are enriched 2 fold in their content of 5 methylcytosine. (Cessation of hydrolysis by nuclease occurs concomitantly with precipitation of nucleosomal core particles).
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PMID:Methylation of nucleosomal and nuclease sensitive DNA. 90

Staphylococcal nuclease (micrococcal nuclease) and pancreatic DNase (DNase I) were used to digest HeLa chromatin core particles which had been labeled with 32P at their 5'-DNA termini. In contrast to DNase I, which cleaves core particle DNA at 10-nucleotide intervals from the 5' termini, staphylococcal nuclease cleaves core particle DNA at different sites, both fewer in number and less regularly spaced. Thus, it is unlikely that simple physical protection of DNA is the sole mechanism whereby chromosomal proteins restrict the nucleolytic cleavage of chromatin; furthermore, it seems likely that these nucleases may recognize different geometric configurations along the chromatin core particle.
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PMID:Staphylococcal nuclease and pancreatic DNase cleave the DNA within the chromatin core particle at different sites. 91 30

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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