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)

Chicken erythrocyte nuclei previously incubated separately with two novel mercury compounds (N-chloromercuribenzoyl)-biocytin and bis(p-(chloromercuribenzoyl))-[3H]lysine diamide) were digested with micrococcal nuclease and the digest products fractionated according to their solubility in 0.15 M NaCl and molecular size. The identity and quantitation of the chromatin fractions and proteins containing covalently bound mercury were determined by Western blotting, autoradiography, and scintillation counting. The most highly acetylated species of histone H3 in the 0.15 M NaCl-soluble polynucleosome fraction also contained the highest proportion of bound mercury. This fraction contains hyperacetylated core histones, is depleted in linker histones, and enriched in nonhistone proteins. Histone H3 in the 0.15 M NaCl-soluble mononucleosomes, which are unacetylated and lack linker histones, was 45% less labeled than histone H3 in the 0.15 M NaCl-soluble polynucleosome fraction. In the 0.15 M NaCl-insoluble polynucleosomes, which contain unacetylated histones and molar proportions of linker histones, histone H3 was 63% less labeled. Allowing for the differential abundance of these subfractions in the nucleus, the relative H3 reactivities are 50, 7, and 1 for 0.15 M NaCl-soluble polynucleosomes, mononucleosomes, and 0.15 M NaCl-insoluble polynucleosomes, respectively. Thus a gradation of reactivities exists which correlates with increasing hyperacetylation and linker histone depletion. High mobility group proteins 1 and 2, found in subnucleosome particles in the 0.15 M NaCl-soluble fraction, are extensively mercury-labeled. Distribution of histone acetyltransferase activity among salt- and size-resolved micrococcal nuclease produced fractions was almost 5-fold greater in the 0.15 M NaCl-soluble supernatant than in the 0.15 M NaCl-insoluble pellet. Furthermore, the acetyltransferase activity, which is tightly bound to undigested chromatin, is rapidly released by both micrococcal nuclease and DNase I. For short digestion times the enzyme is associated with the salt-soluble polynucleosomes, but at longer times of digestion the enzyme appears to be free from intact nucleosomes. The enzyme may be localized in the globin domain in erythrocytes and maintains that region in a hyperacetylated state which results in an altered linker histone binding reflected in a change in the reactivity of the usually inaccessible H3 cysteine 110.
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PMID:Histone H3 thiol reactivity and acetyltransferases in chicken erythrocyte nuclei. 317 Jun 3

Brain cell-free protein synthesis is inhibited by methyl mercury chloride (MeHg) following in vivo or in vitro administration. In this report, we have identified the locus of mercurial inhibition of translation. Intraperitoneal injection of MeHg (40 nmol/g body wt) induced variable inhibition of amino acid incorporation into the post-mitochondrial supernatant (PMS) harvested from the brain of young (10-20-day-old) rats. No mercurial-induced disaggregation of brain polyribosomes nor change in the proportion of 80S monoribosomes was detected on sucrose density gradients. No difference in total RNA was found in the PMS. Initiation complex formation was stimulated by MeHg, as detected by radiolabelled methionine binding to 80S monoribosomes following continuous sucrose density gradient centrifugation. After micrococcal nuclease digestion of endogenous mRNA, both in vivo and in vitro MeHg inhibited polyuridylic acid-directed incorporation of [3H]phenylalanine. However, the in vivo inhibition was no longer observed when [3H]phenylalanyl-tRNAPhe replaced free [3H]phenylalanine in the incorporation assay. The formation of peptidyl[3H]puromycin revealed no difference from controls. There was significant mercurial inhibition of phenylalanyl-tRNA Phe synthetase activity in pH 5 enzyme fractions derived from brain PMS of MeHg-poisoned rats. These experiments revealed that the apparent MeHg inhibition of brain translation in vivo and in vitro is due primarily to perturbation in the aminoacylation of tRNA and is not associated with defective initiation, elongation, or ribosomal function.
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PMID:Experimental methyl mercury neurotoxicity: locus of mercurial inhibition of brain protein synthesis in vivo and in vitro. 384 56

The long-wavelength positive CD bands of poly[d(A).d(T)] and poly[d(A-T).d(A-T)] become inverted upon the addition of Hg(ClO4)2. Poly[d(A).d(T)] requires higher levels of mercury to undergo inversion than poly[d(A-T).d(A-T)]. Mercurated poly[d(A).d(T)] is digested more rapidly than the control by DNase I or staphylococcal nuclease at low levels of Hg(ClO4)2. Let r identical to [Hg(ClO4)2]added/[DNA-P]. A 4- to 5-fold rate increase occurs with DNase I at r = 0.25; a 2-fold increase with staphylococcal nuclease at r = 0.2. By contrast, digestion of poly[d(A-T).d(A-T)] decreases immediately with increasing r. The noted rate increases appear to be due to a modification of poly[d(A).d(T)] helix structure prior to the chiroptical conversion. The modification is interpreted as a widening of the minor groove, permitting, thus, a better binding of DNase I to its substrate. The overall changes in CD as well as enzymatic digestion rates are taken to signal mercury-induced alterations in helix screwness from right-to-left. They are totally reversible subsequent to the removal of mercury.
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PMID:Differential effect of Hg(II) on [d(A)n.d(T)n] and [d(A-T)n.d(A-T)n] sequences: circular dichroism (CD) measurements and endonuclease digestion studies using poly[d(A).d(T)] and poly[d(A-T).d(A-T)] as substrates. 839 52