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

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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)

The expression of the gene coding for chromosomal protein HMG-17 is down regulated during chicken erythrocyte maturation. The transcriptional down regulation is associated with major alterations in the chromatin structure of this gene. The 5' region of the gene contains both constitutive and developmental stage-specific deoxyribonuclease I (DNase I) hypersensitive sites. The constitutive sites bracket the "CpG island" present in the gene, which remains hypomethylated throughout the various developmental stages. During erythropoiesis, the gene acquires a distinct structure that, upon digestion with micrococcal nuclease (MNase) yields an unusual repeat. Two nucleosomes, with a 200 base-pair repeat, are positioned immediately downstream from the start of transcription. Immediately downstream and upstream from these nucleosomes, the boundaries between MNase sites change to a 75 base-pair repeat, which indicates an unusual chromatin structure. The differentiation related changes in the DNase I and MNase digestion pattern in the 5' region of the gene suggest that sequences present in the first intron may be involved in gene regulation. The results may be relevant to the regulation of the entire HMG-14/-17 gene family.
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PMID:Differentiation-dependent alteration in the chromatin structure of chromosomal protein HMG-17 gene during erythropoiesis. 198 81

The chromatin-bound histone deacetylase of Chinese hamster ovary cells has been studied by using as a substrate an acetylated amino-terminal peptide of histone H4. These studies demonstrate that histone deacetylase activity is associated with mononucleosomes solubilized by digestion with micrococcal nuclease. The deacetylase activity remained bound to the nucleosomes, even in the presence of 1 M NaCl. This unique class of deacetylase-associated mononucleosomes is resolved from the major classes of mononucleosomes by polyacrylamide gel electrophoresis. These mononucleosomes contain 290 and 190 base pair DNAs and demonstrate the presence of histone H1 and non-histones HMG-1 and HMG-2 and the absence of HMG-14 and HMG-17. They are further characterized by a specific acetylation pattern of histone H4 and likely represent a functionally important chromatin-DNA complex.
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PMID:A Chinese hamster ovary cell histone deacetylase that is associated with a unique class of mononucleosomes. 344 54

Nucleosomes composed of 195 base pairs of DNA associated with histones H2A, H2B, H3, and H4 purified from chicken erythrocyte nuclei were used to elicit antibodies in rabbits. Specific serological reaction between the antisera and the nucleosomes is demonstrated by immunodiffusion, immunofluorescence, microcomplement fixation, solid-phase radioimmunoassay, immunosedimentation, and polyacrylamide gel electrophoresis of 5'-32P end-labeled nucleosomes. The antisera did not react with DNA extracted from these nucleosomes, core histones, or the cross-linked histone octamer from chicken erythocytes, calf thymus total histones, or chromosomal proteins HMG-1 or HMG-17. Nucleosome antigenicity was not affected by redigestion with micrococcal nuclease. Digestion with DNase I brought about 50% loss of reactivity while digestion with trypsin or proteinase K resulted in total loss of activity. The antisera reacted strongly with trimer, dimer, and monomer nucleosomes as well as with the core particle (145 base pairs of DNA) and subnucleosome (greater than 145 base pairs) obtained from chicken. It reacted less well with nucleosomes obtained from HeLa cells and was almost totally devoid of activity against chromatin particles obtained from rat liver or wheat germ. Experiments employing the technique of transferring proteins from a polyacrylamide gel to diazobenzyloxymethyl paper and visualization of antigens by autoradiography excluded the possibility that the serum contains antibodies against tissue-specific antigens which are found in small amounts but are very immunogenic. It is concluded that most of the anitbodies in the sera are directed against nucleoprotein antigenic determinants composed of the N-terminal portion of the histones and segments of DNA. Antibody binding is dependent on contact between the histone and DNA segments and is independent of the integrity of the entire nucleosome. Thus, certain histone DNA contacts remain intact even though the structure of the nucleosome has been disrupted.
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PMID:Chromatin subunits elicit species-specific antibodies against nucleoprotein antigenic determinants. 615 7

When 125I-labeled H6 was incubated with trout testis nuclei under conditions of pH and ionic strength approximating those in vivo, the radioactivity bound nearly quantitatively to the chromatin. Under comparable conditions, most non-nuclear proteins do not bind. Binding was neither tissue- nor species-specific, and HMG-17, a mammalian homolog of H6, behaved similarly to H6. The labeled and the endogenous H6 molecules were equivalent by several criteria: 1) Both were released nearly quantitatively upon treatment of the chromatin with DNase I, whereas neither was released by digestion with micrococcal nuclease, suggesting that the labeled molecules, like those of endogenous H6, were bound primarily to the core particles in transcriptionally competent portions of the genome. 2) Salt extraction curves were similar for both the labeled and unlabeled proteins, although about 15% of the labeled molecules were bound to the chromatin more loosely than those of the endogenous H6. Taken together, these results suggest that chromatin contains specific, well defined sites to which H6 binds. Upon increasing the concentration of H6 in the incubation mixture, progressively greater numbers of low affinity, presumably nonspecific binding sites become occupied. This observation has important implications for studies in which nucleases are employed to probe chromatin structure, since they suggest that H6 molecules released from specific, high affinity sites by the action of the nuclease might rebind more loosely to other regions of the chromatin.
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PMID:Binding of the high mobility group protein, H6, to trout testis chromatin. 644 56

Chromosomal protein HMG-17, purified from calf thymus, has been used to elicit specific antibodies in rabbits. Specific serological reaction between the antigen and the antisera is demonstrated by solid-phase radioimmunoassay and by competitive inhibition assays. The antisera did not cross-react with histones or other chromosomal HMG proteins. The antisera bound specifically to chromatin subunits isolated from HeLa cells, demonstrating that it may be used to study the in situ organization of this chromosomal protein. Chromatin purified from HeLa nuclei was digested with micrococcal nuclease, and the resulting mono- and oligonucleosomes were fractionated on a sucrose gradient. Analyses of the content of chromosomal proteins HMG-1, HMG-17, and H4 in different size nucleosomal particles, by the solid-phase radioimmunoassay, reveal that the distribution of HMG-17 was the same as that of H4, but different from that of HMG-1.
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PMID:Immunochemical detection of chromosomal protein HMG-17 in chromatin subunits. 645 61

The protein composition of nucleosome fractions differing in their sensitivity to micrococcal nuclease and derived from butyrate-treated or untreated HeLa cells has been compared. Most of the high-mobility-group-14 (HMG-14) and HMG-17 content of HeLa cell chromatin is associated with those nucleosomes that are preferentially sensitive to micrococcal nuclease. Furthermore, electrophoresis of these two HMG proteins from the transcriptionally active chromatin fraction MN1 of butyrate-treated cells resolves them into a series of bands. The multiple band pattern of HMG-14 and -17 from butyrate-treated cells results from hyperphosphorylation rather than hyperacetylation. Phosphorylation of these two small nonhistone proteins may play some role in the modulation of the structure of transcriptionally active chromatin.
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PMID:Enhanced phosphorylation of high-mobility-group proteins in nuclease-sensitive mononucleosomes from butyrate-treated HeLa cells. 645 41

Calf thymus chromatin was fractionated by the Sanders' procedure ((1978) J. Cell Biol. 79, 97-109). this procedure involves sequential elutions of micrococcal nuclease-digested nuclei with buffers of increasing ionic strength. Through the use of the nuclei nick translation technique of Levitt et al. (Levitt, A., Axel, R., and Cedar, H. (1979) Dev. Biol. 69, 496-505) which specifically labels the transcriptionally competent regions of the chromosome, the lowest salt eluted, micrococcal nuclease-sensitive chromatin fraction, was found to be enriched in transcriptionally competent chromatin. This chromatin fraction contained approximately equimolar amounts of the core histones and low amounts of histone H1. In addition, this fraction was enriched both in the acetylated species of histone H4 and in the high mobility group (HMG) proteins 14 and 17, but it was depleted in 5-methylcytosine. As the ionic strength of the elution buffers increased, chromatin fractions from less micrococcal nuclease-sensitive chromatin domains were eluted. The nuclease-insensitive fractions were enriched in the unacetylated species of histone H4, 5-methylcytosine, and histone H1. Although these fractions had a smaller proportion of nucleosomes containing HMG-14 and HMG-17, they contained about 50% of the total HMG-14 and HMG-17 population.
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PMID:Chemical composition of nucleosomes among domains of calf thymus chromatin differing in micrococcal nuclease accessibility and solubility properties. 645 37

Monomer nucleosomes released from nuclei during brief micrococcal nuclease digestions are enriched in transcribed sequences (Bloom and Anderson, 1978). These nucleosomes are depleted in H1 and enriched in three high mobility group proteins HMG14, HMG17 and another HMG-like protein. Analysis of such nucleosomes by polyacrylamide gel electrophoresis reveal that they are heterogenous. Similarly, monomer nucleosomes soluble in 0.1 M NaCl separate on polyacrylamide gels into mainly two types of particle, one of which has HMG14 and HMG17 bound. However, the DNA of the HMG-nucleosomes from chick erythrocytes is not enriched in globin sequences, suggesting that protein rearrangement may have occurred.
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PMID:The high mobility group proteins and transcribed nucleosomes. 722 39

We have reported previously that five different electrophoretic forms of mononucleosomes (MI to MV) are produced upon treatment of mammalian chromatin with micrococcal nuclease. We show here that each of these mononucleosome classes possesses internal heterogeneity due to the presence of a variety of minor protein species. Defined subsets of mononucleosome classes MII to MV have been reconstituted by reassociating stripped nucleosomes with histone H1 and non-histone protein HMG-17. This procedure leads to the generation of the same five major electrophoretic forms of mononucleosomes found in native chromatin. From the results of one- and two-dimensional electrophoretic analyses on reconstituted samples, it is concluded that different mononucleosome classes possess the following subunit structures: MI, core histone octamer (8-mer); MII, 8-mer plus one copy of HMG-17; MIIIA, 8-mer plus one copy of histone H1; MIIIB, 8-mer plus two copies of HMG-17; MIV, 8-mer plus one copy each of histone H1 and HMG-17; and MV, 8-mer plus one copy of histone H1 and two copies of HMG-17. Equal numbers of HMG-14 molecules can substitute for HMG-17 and generate the same nucleosome components. Thus, mononucleosomes possess independent binding sites for at least 1 histone H1 molecule and 2 nonhistone chromosomal protein molecules. We show further that reassociated HMG-17 molecules can exhibit a rapid interchange between binding sites, even under conditions of low ionic strength.
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PMID:Subunit structures of different electrophoretic forms of nucleosomes. 736 65

The rapid, transient induction of 80-100 immediate-early (IE) genes upon mitogenic stimulation occurs irrespective of protein synthesis and is mediated by modification of existing proteins. Two mechanisms, not mutually exclusive, involving modification either of sequence-specific transcription factors or of structural chromatin proteins primed by pre-association with responsive effectors are conceivable. Here, we show that upon IE gene induction, the non-histone high-mobility-group protein HMG-14, but not the related protein HMG-17, becomes serine phosphorylated in its basic, amino-terminal region close to where it binds nucleosomal DNA. Phosphorylation, normally transient, occurs independent of transcription and is quantitative and prolonged during superinduction. Brief micrococcal nuclease digestion substantially releases HMG-14 from nuclei in the mononucleosome-bound state. Finally, mononucleosomes prepared from mitogen-stimulated, but not control, cells contain a mitogen-activated kinase that phosphorylates HMG-14 in vitro on the same site(s) as in intact cells. The association of HMG-14 and its mitogen-activated kinase with nuclease-sensitive mononucleosomes has implications for models of mitogen-stimulated IE gene induction.
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PMID:A mitogen- and anisomycin-stimulated kinase phosphorylates HMG-14 in its basic amino-terminal domain in vivo and on isolated mononucleosomes. 792 94


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