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:3.1.21.1 (DNase)
7,655 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

When chromatin matrix, "stripped" from its loosely-bound components by extraction with 3 M NaCl, is extensively digested with DNAase I, a fraction is obtained, which carries no endogenous DNA methyltransferase activity but which is a good substrate for externally added enzyme. Under the same conditions, protein-free DNA isolated from this fraction can instead hardly be methylated, this different behaviour pointing to a role of DNA-tightly-bound proteins in favoring or promoting the catalytic action of the enzyme. A similar stimulation of enzymatic methylation could also be shown when, in the presence of this same fraction, single stranded Micrococcus luteus DNA was incubated with placental methyltransferase, using S-adenosylmethionine as a methyl donor. This finding can be correlated to the existence, in chromatin loops, of small regions which resist digestion by DNAase I also after high-salt removal of their loosely-bound components (presumably because of the presence of tightly-bound proteins) and whose DNA is characterized by high methylation levels and, at the same time, by high relative content of thymine.
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PMID:Do tightly-bound chromatin proteins play a role in DNA methylation? 325 63

The nuclear matrix (NM) is a salt and nuclease-resistant nuclear substructure. It is associated with active DNA transcription and has been shown to contain acceptor sites for steroid receptors in a number of specific target tissues. We have investigated the presence of acceptor sites for the androgen receptor (AR) in the NM of human newborn foreskin. The NM was prepared from the 800 g pellet by successive treatments with detergent, DNase and high salt extraction. It contained 13 +/- 7% of total proteins and 10 +/- 6% of total DNA. After extensive washing, the NM spheres were incubated in the presence of cytosol and [3H]methyltrienolone +/- 200-fold excess of unlabeled steroid. Maximal binding of the AR to NM was reached in 30 min and decreased slightly thereafter to reach an equilibrium which was maintained for 18 h. Binding was saturable. In the absence of AR, the steroid did not bind to NM. When Scatchard analysis was performed on cytosol previously incubated with NM, cytosolic binding capacity significantly decreased relative to preincubation values (3.6 +/- 1.9 to 1.3 +/- 1.2 fmol/mg protein, P less than 0.05, n = 6). In contrast, apparent binding affinity was not changed. 0.8 mg of NM protein could bind AR from 2.4 mg of cytosol protein. In conclusion, NM from human foreskin binds the AR with high affinity. This binding is rapid and is maintained for at least 18 h. This is consistent with a potential role of NM in the mechanism of action of androgens in their target tissues.
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PMID:Binding of the androgen receptor to the nuclear matrix of human foreskin. 326 Mar 8

We have produced monoclonal antibodies against purified nuclei from the yeast Saccharomyces cerevisiae and have characterized three different antibodies that recognize a protein with an apparent molecular weight of 38,000, termed p38. Subcellular fractionation shows that virtually all of p38 occurs in the nuclear fraction. High concentrations of salt (1 M) or urea (6 M) effectively solubilize p38 from a nuclear envelope fraction prepared by digestion of nuclei with DNase. Indirect immunofluorescence demonstrates a crescent shaped distribution of p38 at the inner periphery of the nucleus, with p38 extending between dividing pairs of cells during (closed) mitosis. Postembedding immunogold electron microscopy shows decoration of the densely stained "crescent" region of the yeast nucleus, confirming the localization of p38 to the nucleolus. One of the monoclonals, D77, cross reacts on immunoblots with a single protein of molecular weight 37,000 from purified rat liver nuclei. Indirect immunofluorescence localizes this protein to the nucleolus, and shows that it is dispersed throughout the cell during mitosis. The yeast and rat liver nucleolar proteins behave similarly when electrophoresed in two dimensions, and appear to have basic pI values. Analysis of immunological cross-reactivity using D77, and antibodies specific for nucleolar proteins from other sources, suggests that the rat liver protein is fibrillarin, and demonstrates that p38 shares epitopes with fibrillarin, as well as with other vertebrate nucleolar proteins.
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PMID:Identification and characterization of a yeast nucleolar protein that is similar to a rat liver nucleolar protein. 329 39

A cell-free system was used to characterize the binding reaction between the progesterone receptor and nuclear acceptor sites prepared from rat placenta. Two forms of receptor-acceptor complex were examined. One was extracted from nuclei by exposure to 0.6 M KCl; the other type was resistant to salt extraction. Kinetic analysis indicated that the binding reactions were saturable (3-4 pmol binding sites/mg DNA) and of high affinity (Kd = 3-6 nM). Acceptor binding was specific for placental nuclei and did not occur with nuclei prepared from spleen or with denatured nuclei from placenta. Acceptor sites were further characterized by their sensitivity to RNase, DNase I, and protease. RNase treatment had no influence on receptor-acceptor binding. However, DNase I reduced the number of KCl-resistant acceptor sites by 41%, but only a 19% reduction occurred in KCl-extractable acceptor sites (P less than 0.05). Protease removed 34% and 48% of the KCl-resistant and -extractable acceptor sites, respectively, and combined treatment with DNase and protease eliminated 76% of acceptor-binding activity. The endogenous inhibitor previously described from rat placental cytosol blocked acceptor-binding sites in a concentration-dependent manner, a decrease of 1.15 pmol sites/mg inhibitor protein for resistant sites and 0.76 pmol/mg inhibitor protein for extractable sites. However, receptor-acceptor binding was not altered by treating nuclei with actinomycin D or chloroquine. Mercurial reagents reduced receptor-acceptor interaction by 80% and 94% in KCl-resistant and -extractable sites, respectively, whereas sulfhydryl alkylating agents reduced binding 35% and 76%. Pyridoxal phosphate destroyed 88-93% of acceptor binding. The results of these studies suggest that the progesterone receptor acceptor sites are composed of a complex of chromatin protein and DNA in rat placenta. Furthermore, the binding reaction requires the participation of sulfhydryl and terminal amino groups.
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PMID:Nuclear acceptor sites for progesterone-receptor complexes in rat placenta. 329 40

A comparative study of the interaction of the LexA repressor of Escherichia coli and of its amino-terminal DNA binding domain to the uvrA operator has been undertaken. Most of the binding constants are determined from competition experiments with RNA polymerase by measuring the time-course of the abortive initiation transcriptional activity. The presence of repressor increases the lag time, tau, without affecting the final maximum activity. The inhibition of transcription by LexA, at least in the case of the uvrA gene, is thus a transient, time-dependent phenomenon, because once the RNA polymerase is engaged in a stable "open" complex, it is quasi-irreversibly trapped in this state. A study of the binding constants as a function of ionic strength suggests the formation of 5.5(+/- 1) salt bridges between the uvrA operator and a LexA dimer. Surprisingly, the binding affinity of the amino-terminal domain was only about one order of magnitude smaller than that of the entire LexA repressor. The determination of the binding constant of the RNA polymerase to the "closed" uvrA promoter (KB approximately 1 X 10(7) to 2 X 10(7) M-1) allowed us to determine theoretical repression curves for the two repressor species. These calculations show that the binding constant found for LexA is sufficiently high to account for substantial or complete repression, and that of the amino-terminal domain is sufficiently low to account for partial or nearly full induction. Under solvent conditions used by others for the determination of binding constants to other SOS operators by DNAase I footprinting, the uvrA operator turns out to be a rather weak one (K approximately 3 X 10(7) M-1), being comparable with that of the uvrB gene. The uvrA promoter is "association-limited" with a KB X k2 product fitting very nicely the homology score for the promoter of 55.
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PMID:Promoter properties and negative regulation of the uvrA gene by the LexA repressor and its amino-terminal DNA binding domain. 329 58

The bacteriophage T3 DNA packaging system in vitro defined here is composed of purified proheads and two non-capsid proteins, the products of genes 18 and 19 (gp18 and gp19). In this system, a precursor complex (50 S complex) accumulates in the presence of adenosine 5'-O-(3'-thiotriphosphate) (ATP-gamma-S), a non-hydrolyzable analog of ATP. The 50 S complex is converted to a filled head in the presence of ATP. The conversion of the 50 S complex, formed by preincubation with ATP-gamma-S, to the mature head proceeds in a synchronous manner after the addition of ATP. The lag time for formation of mature heads from the 50 S complex is 1.8, 4.5 and 6.8 minutes at 30, 25 and 20 degrees C, respectively. DNA is translocated into the capsid at a constant rate of 5.7 x 10(3) base-pairs per minute at 20 degrees C. The conversion of the 50 S complex to the mature head exhibits a sigmoidal relationship with respect to the concentration of ATP, the concentration for half-maximal activity being about 20 microM. The transition of the prohead to the expanded capsid occurs at 20 degrees C at one minute 40 seconds after the initiation of DNA translocation, when one-fourth of the genome has been packaged into a prohead. At the same time, the capsid-DNA complex becomes stable to high concentrations of salt. When DNA translocation is interrupted by the addition of ATP-gamma-S, packaged DNA exists at 0 degrees C as well as at 20 degrees C but the exit of DNA stops after one-third of the genome is inside the capsid. After exit, DNA is retranslocated into the expanded capsid by the addition of ATP at a rate of about 5.7 x 10(3) base-pairs per minute at 20 degrees C. The decrease in concentration of ATP interrupts DNA translocation into the capsid but does not induce DNA exit. Interrupted DNA translocation may be reinitiated by the addition of ATP. DNA exit is not induced by the addition of ATP-gamma-S to mature heads or partially filled heads pretreated with DNase.
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PMID:Characterization of the bacteriophage T3 DNA packaging reaction in vitro in a defined system. 331 64

Rabbits were injected intracerebrally with aluminum salt leading to experimental neurofibrillary change formation as a model of Alzheimer neurofibrillary change. Eleven days after the injection, the brain tissues were excised from the cortex, hippocampus, and cervical region of spinal cord. Five lysosomal enzymes (cathepsin D, beta-glucuronidase, acid phosphatase, acid DNase, alkaline DNase) were assayed and compared with the control. Cathepsin D, acid DNase and beta-glucuronidase activities increased significantly in all 3 areas of aluminum-injected brain. On the other hand, acid phosphatase and alkaline DNase activities remained at the same level. The results showed the lysosomal enzymes did not change in parallel after aluminum administration, suggesting a role of the increased enzymes in the brain with neurofibrillary changes.
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PMID:Activities of lysosomal enzymes in rabbit brain with experimental neurofibrillary changes. 339 97

The chromatin of several genes was assayed for sensitivity to DNAase I and for solubility as polynucleosomes in 0.15 M NaCl. The degree of solubility of chromatin fragments as polynucleosomes in 0.15 M NaCl correlates well with the sensitivity to DNAase I for several genes. Chromatin of repressed, housekeeping and erythroid-specific genes can be distinguished as distinct groups by the degree to which they display these properties. NaCl precipitation of chromatin fragments stripped and then reconstituted with varying quantities of H1 and H5 (linker) histones indicate that the polynucleosomes of erythroid-specific genes have altered interaction with these histones. Linker histones interacted with bulk chromatin and in the chromatin of the repressed ovalbumin and vitellogenin genes to form salt precipitable structures. Chromatin of erythroid-specific genes (histone H5 and beta-globin) as well as that of the histone H2A.F gene was resistant to linker histone induced precipitation.
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PMID:Erythroid-specific gene chromatin has an altered association with linker histones. 339 83

The properties of the viral and cellular fos proteins (Fos) were investigated as a first step toward understanding the function of the fos gene. Treatment of nuclei with salt and nonionic detergents solubilized a complex that contained Fos together with several other cellular proteins. The majority of the Fos protein complex was released from isolated nuclei incubated in the presence of deoxyribonuclease I or micrococcal nuclease but not with ribonuclease A, suggesting that Fos is associated with chromatin. This hypothesis is supported by the finding that Fos protein from native or denatured nuclear extracts exhibited DNA-binding activity in vitro. These results suggest that Fos is involved in the regulation of gene expression.
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PMID:The Fos protein complex is associated with DNA in isolated nuclei and binds to DNA cellulose. 349 27

Nuclear matrix prepared from mouse leukemia L5178Y cells contained not only the two common actin isomers, beta and gamma actins, but also two additional acidic species of actin (pI 5.1 and 5.3). An anti-actin antibody recognized these acidic species as well as beta and gamma actins on a nitrocellulose filter following western blotting of two-dimensional electrophoresis. These acidic species were co-purified with beta and gamma actins using DNase I-Sepharose affinity chromatography on the nuclear matrix. Limited digestion of the acidic actin with protease V8 or trypsin gave very similar peptide fragments as did digestion of beta and gamma actins. These acidic actins were found to be distributed in the nuclear fraction, but were scarcely detectable in the cytoplasmic fraction. One of the acidic actins (pI 5.3) was found in all subnuclear fractions (DNase extract, high-salt extract and nuclear matrix), while the other species, the most acidic actin (pI 5.1), was localized predominantly in the nuclear matrix.
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PMID:Preferential association of acidic actin with nuclei and nuclear matrix from mouse leukemia L5178Y cells. 351 45


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