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)

The assembly of hybrid core particles onto long chicken DNA with histone H2B in the chicken histone octamer replaced with either wheat histone H2B(2) or sea urchin sperm histone H2B(1) or H2B(2) is described. All these histone H2B variants have N-terminal extensions of between 18 and 20 amino acids, although only those from sea urchin sperm have S(T)PXX motifs present. Whereas chicken histone octamers protected 167 base pairs (bp) (representing two full turns) of DNA against micrococcal nuclease digestion (Lindsey, G. G., Orgeig, S., Thompson, P., Davies, N., and Maeder, D. L. (1991) J. Mol. Biol. 218, 805-813), all the hybrid histone octamers protected an additional 17-bp DNA against nuclease digestion. This protection was more marked in the case of hybrid octamers containing sea urchin sperm histone H2B variants and similar to that described previously (Lindsey, G. G., Orgeig, S., Thompson, P., Davies, N., and Maeder, D. L. (1991) J. Mol. Biol. 218, 805-813) for hybrid histone octamers containing wheat histone H2A variants all of which also have S(T)PXX motifs present. Continued micrococcal nuclease digestion reduced the length of DNA associated with the core particle via 172-, 162-, and 152-bp intermediates until the 146-bp core particle was obtained. These DNA lengths were approximately 5 bp or half a helical turn longer than those reported previously for stripped chicken chromatin and for core particles containing histone octamers reconstituted using "normal" length histone H2B variants. This protection pattern was also found in stripped sea urchin sperm chromatin, demonstrating that the assembly/digestion methodology reflects the in vivo situation. The interaction between the N-terminal histone H2B extension and DNA of the "linker" region was confirmed by demonstrating that stripped sea urchin sperm chromatin precipitated between 120 and 500 mM NaCl in a manner analogous to unstripped chromatin whereas stripped chicken chromatin did not. Tryptic digestion to remove all the histone tails abolished this precipitation as well as the protection of DNA outside of the 167-bp core particle against nuclease digestion.
...
PMID:S(T)PXX motifs promote the interaction between the extended N-terminal tails of histone H2B with "linker" DNA. 163 9

The preparation of hybrid histone octamers with wheat histone H2A variants replacing chicken H2A in the chicken octamer is described. The fidelity of the reconstituted hybrid octamers was confirmed by dimethyl suberimidate cross-linking. Polyglutamic-acid-mediated assembly of these octamers on long DNA and subsequent micrococcal nuclease (MNase) digestion demonstrated that, whereas chicken octamers protected 167 base-pairs (representing 2 full turns of DNA), hybrid histone octamers containing wheat histone H2A(1) with its 19 amino acid residue C-terminal extension protected an additional 16 base pairs of DNA against nuclease digestion. The protection observed by hybrid histone octamers containing wheat histone H2A(3) with both a 15 residue N-terminal and a 19 residue C-terminal extension was identical with that observed with H2A(1)-containing hybrid histone octamers with only the 19 residue C-terminal extension. These results suggest that the role of the C-terminal extension is to bind to DNA of the "linker" region. The thermal denaturation of chicken and hybrid core particles was identical in 10 mM-Tris.HCl.20 mM-NaCl, 0.1 mM-EDTA, confirming that there was no interaction between the basic C-terminal extension and DNA of the core particle. Denaturation in EDTA, however, showed that hybrid core particles had enhanced stability, suggesting that the known conformational change of core particles at very low ionic strength allows the C-terminal extension to bind to core particle DNA under these conditions. A model accounting for the observed MNase protection is presented.
...
PMID:Extended C-terminal tail of wheat histone H2A interacts with DNA of the "linker" region. 202 50

We recently demonstrated that ubiquitinated histone H2A (uH2A) declines 2.5-fold during terminal skeletal muscle differentiation, coincident with reductions in transcriptional activity (Wunsch, A. M., Haas, A. L., and Lough, J. (1987) Dev. Biol. 119, 85-93). To assess whether this indicates an association of uH2A with transcriptionally active genes, we have used micrococcal nuclease digestion and salt extraction to fractionate myotube nuclei. An oligonucleosomal fraction obtained by micrococcal nuclease digestion and extraction in low salt (100 mM NaCl) comprising only 25% of the nuclear DNA contained 90% of the total uH2A, as revealed by Western blotting. Further fractionation of this 100 mM salt extract by sucrose gradient centrifugation revealed that virtually all of the uH2A was localized in monomer to heptamer-sized oligonucleosomes. A second ubiquitinated species of 57-kDa (u57) was also localized in the 100 mM salt extract. In contrast, an 18-kD band (u18) was associated with fractions that were resistant to micrococcal nuclease digestion and salt extraction. Although micrococcal nuclease recognized a unique structural feature of active myotube chromatin, as evidenced by the appearance of hybridized skeletal alpha-actin sequences as a smear rather than the nucleosomal ladder exhibited by inactive and bulk sequences, neither the skeletal alpha-actin gene nor the inactive alpha D-globin gene was exclusively localized in the 100 mM salt fraction. Moreover, further fractionation of the 100 mM salt extract on a sucrose gradient failed to separate active from inactive genes. These findings suggest that uH2A is localized in a fraction of myotube chromatin which, although nuclease-sensitive and relatively soluble, is not enriched in active or inactive genes.
...
PMID:Enrichment of ubiquitinated histone H2A in a low salt extract of micrococcal nuclease-digested myotube nuclei. 215 2

Three major satellite DNAs comprise 40-45% of the genome of Drosophila virilis. Since these satellites are not substrates for most restriction enzymes, we were able to digest D. virilis nuclei with HaeIII and micrococcal nuclease and isolate chromatin fractions containing variable levels of satellite DNA. Electrophoretic analysis of these chromatin fractions revealed that the level of the acid-soluble chromosomal protein, cp17.3, was directly related to the percentage of satellite DNA in chromatin. The correlation between cp17.3 and satellite DNA abundance suggests that cp17.3 is involved in the heterochromatic condensation of satellite DNAs. cp17.3 occurs at a frequency of one molecule per 10-20 nucleosomes. It is detected in an electrophoretically distinguishable class of mononucleosomes, provisionally identified as MN1uH2A, which contains ubiquitinated histone H2A (uH2a) but lacks histone H1. It is not detected in MN1, a second class of mononucleosomes, which lacks uH2A and H1. Since cp17.3 is correlated with satellite DNAs and present in nucleosome cores, it might be a histone variant specifically associated with satellite DNAs.
...
PMID:Satellite DNA-correlated nucleosomal proteins in Drosophila virilis. 300 8

By means of selective micrococcal nuclease digestion chromatin from early stages of the sea urchin St. droebachiensis embryogenesis was divided into fractions differing by their transcriptional activity. The electrophoretic analysis of histones at the gastrula stage showed that the transcriptionally active chromatin fraction was enriched with early variants of histone H2A and H1. On the stage of pluteus, when primary cell differentiation is completed, the amount of total histone H1 in this fraction was significantly decreased, however it was enriched in an early alpha variant. It was shown that after mild micrococcal nuclease digestion mononucleosomes, which were mostly derived from active chromatin, were significantly enriched with in vivo labeled early histone variants.
...
PMID:[Nucleosomes of active chromatin from sea urchin embryo cells are rich in early histone variants]. 337 87

Chromatin fractions differing in their transcriptional activity were isolated by selective micrococcal nuclease digestion of nuclei from sea urchin embryos (Strongylocentrotus droebachiensis) at the gastrula and pluteus stage. The electrophoretic analysis of the chromatin proteins at the gastrula stage showed that a soluble, transcriptionally active fraction of chromatin was enriched with early variants of histones H1 and H2A. The early and late variants of histone H2A at the pluteus stage were distributed randomly between chromatin fractions. However, the content of both variants of histone H1 was essentially decreased in the soluble transcriptionally active fraction of chromatin.
...
PMID:Distribution of histone variants in the sea urchin chromatin fractions obtained by selective micrococcal nuclease digestion. 406 5

We have a new approach, two-dimensional hybridization mapping of nucleosomes, to compare the structures of mononucleosomes from different regions of the Drosophila melanogaster genome. Approximately one in two nucleosomes of the transcribed copia and heat-shock 70 (hsp 70) genes in nonshocked cultured cells contains ubiquitin-H2A (uH2A) semihistone, a covalent conjugate of histone H2A and a small protein, ubiquitin. In striking contrast, less than one in 25 nucleosomes of tandemly repeated, nontranscribed 1.688 satellite DNA contains uH2A, suggesting that most of the nucleosomal uH2A is located in transcribed genes. Approximately 25% of all nucleosomes are ubiquitinated in nonsynchronized cultured Drosophila cells. The hsp 70 genes in nonshocked cells occur in nucleosomes, are greatly enriched in uH2A and are not digested preferentially by staphylococcal nuclease. In contrast, the same genes in chromatin from heat-shocked cells are highly sensitive to staphylococcal nuclease and no longer possess nucleosomal organization recognizable with this probe. Histone ubiquitination in transcribed nucleosomes may prevent formation of higher order chromosomal structures by modifying nucleosome-nucleosome interactions. The observed loss of nucleosomal organization in very actively transcribed genes, such as the hsp 70 genes in shocked cells, may be related to the recent finding that ubiquitin conjugates are substrates for the cytoplasmic ATP-dependent proteolytic system. We have also found that 1.688 satellite mononucleotomes contain a specific approximately 50,000 dalton nonhistone protein, D1, in addition to being extremely under-ubiquitinated. D1 may be involved in formation of the highly compact structure of satellite heterochromatin.
...
PMID:Selective arrangement of ubiquitinated and D1 protein-containing nucleosomes within the Drosophila genome. 627 12

Infection of BHK cells with foot-and-mouth disease virus (FMDV) causes a thorough change in the electrophoretic profile of whole nuclear histones. It consists in the disappearance of histone H3 and the appearance of a new polypeptide (Pi) which migrates between histones H2A and H4 on SDS-polyacrylamide gels. Protein Pi is detected at 2 hr postinfection (pi), the time in which viral RNA synthesis begins to increase, and reaches equimolecular amounts with the remaining core histones 1 hr later, when the disappearance of histone H3 is almost complete. Labeling of cells prior to infection demonstrates that Pi is not a novo product but the result of a viral-induced processing of a host precursor synthetized beforehand. Protein Pi comigrates with histone H2A/B in acetic acid/urea polyacrylamide gels and it shares common major peptides with histone H3 under controlled proteolysis with protease V8 or trypsin. The mononucleosomal and nucleosomal DNA pattern analysis after micrococcal nuclease treatment of nuclei from infected and mock-infected cells did not show any significant differences even though after 3 hr (p.i.), protein Pi replaces histone H3 in the nucleosomal structure. It was concluded that FMDV infection is responsible for a specific modification in the nucleus of infected cells which leads, after 3 hr (p.i.), to a complete histone H3 protein Pi transition in the nucleosomes.
...
PMID:Histone H3 modification in BHK cells infected with foot-and-mouth disease virus. 633 Sep 87

A histone-like protein (H) from Escherichia coli has been purified to more than 98% homogeneity by using its capacity to inhibit DNA functions. H protein behaves as a dimer of 28,000-dalton subunits. The histone H2A-like properties of H protein are: (i) binding to DNA at a stoichiometry of 1 H protein dimer per 75 bases; (ii) abundance of about 30,000 molecules per cell, sufficient to bind about 20% of the chromosome; (iii) limiting digestion of double-stranded DNA by micrococcal nuclease; (iv) reannealing of complementary single-stranded DNA; (v) amino acid composition resembling that of eukaryotic histone H2A; (vi) neutralization of H protein by antibody specific for H2A; (vii) heat stability; and (viii) acid solubility. The capacity of H protein to bind DNA prevents its template or substrate functions n several reactions in vitro: DNA synthesis by several polymerases; transcription by RNA polymerase; DNA topoisomerase activity; and DNA-dependent ATP hydrolysis by rep protein, dnaB protein, or protein n'. Together with other histone-like proteins of E. coli, H protein may organize the E. coli chromosome into nucleosomes, such as in eukaryotic chromatin.
...
PMID:Novel histone H2A-like protein of escherichia coli. 700 71

We have described earlier a chromatin-bound protease with unique specificity for histone H2A [Eickbush, T. H., Watson, D. K., & Moudrianakis, E. N. (1976) Cell (Cambridge, Mass.) 9, 785--792]. In the present study, we explore the nature of interactions that form and stabilize the enzyme-chromatin system by using the activity of the protease to monitor its binding to DNA and DNA-histone complexes. During salt extraction of chromatin, the protease is released at an ionic strength between that required for the extraction of the slightly lysine-rich histones (H2A and H2B) and the arginine-rich histones (H3 and H4). The reassociation of this nonhistone protein to DNA has an absolute requirement for the H3--H4 tetramer and is only enhanced by the H2A--H2B dimer in the presence of the tetramer. We believe that the binding of the enzyme onto DNA requires some histone-elicited compaction of the helix. We have also examined the distribution of this enzyme within the chromatin fiber by isolating pools of monomer nucleosomes from micrococcal nuclease digests of 0.6 M NaCl extracted chromatin and from reconstituted DNA-protein complexes. The H2A-protease is found with these monomer nucleosome pools, and no activity can be detected in the low molecular weight products released during the digestion. Thus, by virtue of its extraction characteristics from chromatin and its association with isolated nucleosomes, this nonhistone protein exhibits properties hitherto assigned only to the inner histones.
...
PMID:Histone-dependent reconstitution and nucleosomal localization of a nonhistone chromosomal protein: the H2A-specific protease. 704 60


1 2 Next >>

---