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)

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

We have recently shown that, after the histones and most of the nonhistone proteins are gently removed from HeLa metaphase chromosomes, the chromosomal DNA is still highly organized and relatively compact. The structure of these histone-depleted chromosomes is due to the presence of a number of nonhistone proteins that form a central scaffold that retains the approximate size and shape of intact chromosomes and to which the DNA is attached, predominantly forming loops. We now demonstrate that the protein scaffold may be isolated independently of the DNA by treating HeLa chromosomes with micrococcal nuclease before removing the histones.The chromosomal scaffolds may be isolated by sucrose density gradient centrifugation as a well-defined peak that is stable in 2 M sodium chloride, but is dissociated by treatment with proteases, 4 M urea, or 0.1% sodium dodecyl sulfate. Polyacrylamide gel electrophoresis reveals that the protein content of scaffold preparations is identical to that of histone-depleted chromosomes. Fluorescence microscopy of purified scaffolds in isolation buffer shows that the particles still possess the familiar chromosome morphology. When the scaffolds are examined in the electron microscope, a fibrous structure with the approximate size and shape of intact, paired chromatids is seen. Less than 0.1% of the chromosomal DNA and virtually no histones are associated with the purified scaffold structures.
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PMID:Isolation of a protein scaffold from mitotic HeLa cell chromosomes. 27 Jul 27

The gene for staphylococcal nuclease (SNase), an extracellular enzyme of Staphylococcus aureus, was introduced into Corynebacterium glutamicum. The heterologous gene was expressed in this host organism, and SNase was efficiently exported to the culture medium. Amino-terminal sequencing of SNase secreted by C. glutamicum revealed that the signal peptide was apparently cleaved off at precisely the same position as in the original host, S. aureus. As with S. aureus, a second smaller form of SNase (A form), whose appearance is presumably the result of a secondary processing step, was found in the culture medium of the recombinant C. glutamicum strain. The A form was one residue shorter than the mature nuclease A produced by S. aureus. Variation of the sodium chloride concentration in the growth medium had a marked influence on the location and the processing of SNase by C. glutamicum. In a complex growth medium containing 4% sodium chloride, SNase was exclusively located in the supernatant, but a significant amount of the enzyme remained cell associated if the strain was grown in a low-salt medium. Also, high salt concentrations seemed to inhibit processing of the high-molecular-weight form of SNase (B form) to the smaller A form. Similarities and differences in the export and modes of processing of SNase by three different, nonrelated gram-positive host organisms are discussed. Finally, a versatile Escherichia coli-C. glutamicum tac-lacIq expression shuttle vector was constructed. With this vector, it was possible to achieve isopropyl-beta-D-galactopyranoside (IPTG)-inducible overexpression and secretion of SNase in C. glutamicum, whereby the expression level was dependent on the concentration of the inducer.
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PMID:Expression, secretion, and processing of staphylococcal nuclease by Corynebacterium glutamicum. 154 34

The tetrameric (H3/H4)2 146 base pair (bp) DNA and hexameric (H3/H4)2(H2A/H2B)1 146 bp DNA subnucleosomal particles have been prepared by depletion of chicken erythrocyte core particles using 3 or 4 M urea, 250 mM sodium chloride, and a cation-exchange resin. The particles have been characterized by cross-linking and sedimentation equilibrium. The structures of the particles, particularly the tetrameric, have been studied by sedimentation velocity, low-angle neutron scattering, circular dichroism, optical melting, and nuclease digestion with DNase I, micrococcal nuclease, and exonuclease III. It is concluded that since the radius of gyration of the DNA in the tetramer particle and its maximum dimension are very close to those of the core particle, no expansion occurs on removal of all the H2A and H2B. Nuclease digestion results indicate that histones H3/H4 in the tetramer particle protect a total of 70 bp of DNA that are centrally located within the 146 bp. Within the 70 bp DNA length, the two terminal regions of 10 bp are, however, not strongly protected from digestion. The optical melting profile of both particles can be resolved into three components and is consistent with the model of histone protection of DNA proposed from nuclease digestion. The structure proposed for the tetrameric histone complex bound to DNA is that of a compact particle containing 1.75 superhelical turns of DNA, in which the H3 and H4 histone location is the same as found for the core particle in chromatin by histone/DNA cross-linking [Shick, V. V., Belyavsky, A. V., Bavykin, S. G., & Mirzabekov, A. D. (1980) J. Mol. Biol. 139, 491-517]. Optical melting of the hexamer particle shows that each (H2A/H2B)1 dimer of the core particle protects about 22 base pairs of DNA.
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PMID:Structure of subnucleosomal particles. Tetrameric (H3/H4)2 146 base pair DNA and hexameric (H3/H4)2(H2A/H2B)1 146 base pair DNA complexes. 405 8

Nuclease digestion of isolated nuclei was used to test whether differential chromatin structure exists for a dosage-compensated heat shock gene in Drosophila pseudoobscura. No differences were observed in nuclease sensitivity at this locus in males and females, either under heat shock or non-heat shock conditions, using micrococcal nuclease or DNase I. Although the higher level of nuclease sensitivity characterized by the induced state was removed when nuclei were prepared in high salt (0.45 M sodium chloride), this procedure did not reveal covert differences in X-linked chromatin structure between males and females. However, a clear difference was observed in the nuclease sensitivity at low level (uninduced) and high level (heat-induced) expression of the X-linked heat shock gene, suggesting that the same gene transcribed at two steady state rates can have different chromatin structures.
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PMID:Chromatin structure and transcriptional activity of an X-linked heat shock gene in drosophila pseudoobscura. 631 15