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)

Purified nuclei from turnip leaves infected by cauliflower mosaic virus (CaMV) have been shown to contain a fraction of CaMV DNA that consists of covalently closed circular molecules; possesses a nucleosome structure, based on sensitivity to micrococcal nuclease; and contains nuclear RNA polymerase II that selectively transcribes the coding strand of CaMV DNA in vitro. Our results suggest that the transcriptionally active CaMV DNA is in the form of a minichromosome and that this DNA does not contain the site-specific discontinuities characteristic of the virion.
...
PMID:A transcriptionally active, covalently closed minichromosome of cauliflower mosaic virus DNA isolated from infected turnip leaves. 711 45

Chick embryos, chick embryo fibroblasts, and Rous sarcoma virus-transformed chick embryo fibroblasts contain a factor that preferentially blocks the accumulation of DNA-directed RNA polymerase II transcripts. The factor was detected by inhibition of transcription in a cell-free assay system utilizing partially purified RNA polymerase II from calf thymus, soluble factors from HeLa cells, and a purified DNA template. At low concentrations, it specifically prevents the accumulation of RNA polymerase II transcripts; at higher concentrations, it blocks the accumulation of other transcripts. The factor has been partially purified by sequential chromatography on BioRex 70, DNA-cellulose, Bio-Gel P-6, and HPX-87 from extracts of chicken embryos. The activity was resistant to treatment with trypsin, pronase, or micrococcal nuclease. A partial characterization of the molecule indicates that (i) it has an apparent molecular mass of about 200-300 daltons, (ii) it is stable at pH 2 and pH 12 and to heating at 100 degrees C, (iii) it is not extractable by ether or chloroform:methanol, (2:1, v/v), and (iv) it is labile to heating at 800 degrees C. These data suggest that it is a small, hydrolphilic compound probably organic in nature. The factor is active in a transcription assay utilizing either the Rous sarcoma virus Long Terminal Repeat promoter or the chick alpha 2 (Type I) collagen-promoter as DNA templates. The accumulation of promoter-specific transcripts is blocked in a cell-free assay utilizing either Rous sarcoma virus-chick embryo fibroblast extracts or HeLa S-100 factors and calf thymus RNA polymerase II. In the absence of S-100, the factor does not appreciably affect the accumulation of randomly initiated transcripts produced by calf thymus RNA polymerase II on a DNA template; this result indicates the factor interacts directly or indirectly with some component(s) of HeLa S-100 to prevent the accumulation of RNA.
...
PMID:Chicken embryo extracts contain a factor that preferentially blocks the accumulation of RNA polymerase II transcripts in a cell-free system. 713 Jan 91

We have shown that, in rat liver nuclei, the chromatin-bound RNA polymerase II is released as two different forms on digestion with micrococcal nuclease or DNase I (peak 1 and peak 2). To elucidate the origin of the two forms of the enzyme, we examined their distribution in fractionated chromatins obtained by mild micrococcal nuclease digestion of the nuclei. About half of the total peak 2 activity was recovered in a nuclease-sensitive chromatin fraction which contained DNA enriched in the sequences appearing in the polysomal polyadenylated mRNA. On the other hand, four-fifths of the total peak 1 activity was recovered in a nuclease-resistant chromatin fraction which contained DNA comprising only two thirds of the transcribed sequences. Furthermore, during the nuclease digestion, peak 2 activity was rapidly released from the chromatin, whereas peak 1 activity was gradually released. These results indicate that the two forms of RNA polymerase II are distributed differently in the cell nuclei.
...
PMID:Characteristic distribution of two forms of chromatin-bound RNA polymerase II in rat liver nuclei. 714 14

Two forms of RNA polymerase II were released from rat liver chromatin by micrococcal nuclease digestion of the nuclei. One from behaved like a free RNA polymerase II and the other like a complex with other nuclear components. Both forms of RNA polymerase II activity were recovered in the 0.16 M NaCl-soluble fraction of the nuclear digest, and the complexed from the RNA polymerase II could transcribe its endogenous template under conditions permitting only of elongation of the RNA synthesis. The RNA polymerase II complex was further purified by gel filtration chromatography and column electrophoresis. Analysis of protein and DNA of the partially purified complex suggested that the RNA polymerase II was bound to mono- or dinucleosomes carrying some characteristic nonhistone proteins. Furthermore, in experiments on tissues from starved rats, the two forms of RNA polymerase II were found to originate from different functional states of the chromatin-bound enzyme in vivo.
...
PMID:Partial characterization of RNA polymerase II complex released by micrococcal nuclease digestion of rat liver nuclei. 721 38

Nuclei purified from C57BL mouse submandibular salivary gland were treated with a range of micrococcal nuclease concentrations and times of treatment (from 0.5 unit for 2.5 min to 50 units for 30 min) in the presence of polyamines. About 50% of the chromatin was solubilized initially but with prolonged digestion this chromatin became insoluble again. Electron microscopy showed destruction of the finely dispersed chromatin with mild digestion, followed by aggregation of chromatin with more vigorous digestion. The early disappearance of finely dispersed chromatin filaments was not accompanied by preferential solubilization of chromatin associated with RNA polymerase II (euchromatin). These data suggest that the polyamines markedly reduce the susceptibility of euchromatin to micrococcal nuclease digestion.
...
PMID:Ultrastructural studies on chromatin digestion by micrococcal nuclease in the presence of polyamines. 727 86

The presence of actin in eukaryotic nuclei, and, especially, its functional significance has not been well established. We have found that under routine immunocytochemical conditions, no actin can be detected in insect follicle cell nuclei by means of antibody (both mono- and polyclonal) or phalloidin staining. However, a pretreatment of nuclear preparations with two different endonucleases (deoxyribonuclease I or micrococcal nuclease) to remove a substantial amount of chromosomal DNA uncovers the presence of nuclear actin for both antibody and phalloidin detection. Employing the same nuclease digestion followed by antibody or phalloidin staining with squash preparations of Drosophila polytene chromosomes revealed that the nuclear actin is directly associated with the chromosomes. A strong positive signal in the polytene chromosomes obtained with phalloidin labeling not only confirmed the presence of actin in the chromosomes, but indicates that a considerable amount of nuclear actin is present in filamentous form (F-actin) rather than monomeric (G-actin). The detection of actin associated with Xenopus embryo chromosomes suggests the significance of chromosomal actin for diploid vertebrate cells. Using the specific actin disrupting agent cytochalasin D, we have demonstrated the structural significance of nuclear actin in maintaining the linear integrity of polytene chromosomes. Further, we present evidence that RNA polymerase II closely interacts with the chromosomal actin scaffold, and that its association with chromosomes does not require the presence of DNA.
...
PMID:An actin infrastructure is associated with eukaryotic chromosomes: structural and functional significance. 752 80

Replication of hepadnaviruses requires a persistent population of covalently closed circular (CCC) DNA molecules in the nucleus of the infected cell. It is widely accepted that the vital role of this molecule is to be the sole DNA template for the synthesis by RNA polymerase II of all viral transcripts throughout the infection process. Since the transcriptional activity of eukaryotic nuclear DNA is considered to be determined in part by its specific organization as chromatin, the nucleoprotein disposition of the hepadnavirus CCC DNA was investigated. These studies were undertaken on the duck hepatitis B virus (DHBV) CCC DNA present in the liver cell nuclei of DHBV-infected ducks. The organization and protein associations of the DHBV CCC DNA in situ were inferred from sedimentation, micrococcal nuclease digestion, and DNA superhelicity analyses. These three lines of investigation demonstrate that the DHBV CCC DNA is stably associated with proteins in the nuclei of infected liver cells. Moreover, they provide compelling evidence that the viral nucleoprotein complex is indeed a minichromosome composed of classical nucleosomes but in arrays that are atypical for chromatin. When the DHBV chromatin is digested with micrococcal nuclease, a ladder of viral DNA fragments that exhibits a 150-bp repeat is produced. This profile for the viral chromatin is obtained from the same nuclei in which the duck chromatin shows the standard 200-bp ladder. The superhelicity of the DHBV CCC DNA ranges from 0 to 20 negative supertwists per molecule, with all possible 21 topoisomers present in each DNA preparation. The 21 topoisomers of DHBV CCC DNA are inferred to derive from an identically diverse array of viral minichromosomes. In the DHBV minichromosomes composed of 20 nucleosomes, 96.7% of the viral DNA is calculated to be compacted into these chromatin subunits spaced on average by 5 bp of linker DNA; other minichromosomes contain fewer nucleosomes and proportionately more linker DNA. Two major subpopulations of DHBV minichromosomes are detected with comparable prevalence. The two groups correspond to minichromosomes which contain essentially a full or half complement of nucleosomes. The functional significance of this minichromosome diversity is unknown but is suggestive of transcriptional regulation of the viral DNA template.
...
PMID:The covalently closed duplex form of the hepadnavirus genome exists in situ as a heterogeneous population of viral minichromosomes. 774 82

Most DNA topoisomerase II (topo II) in cell-free extracts of 0-2-h old Drosophila embryos appears to be nonnuclear and remains in the supernatant after low-speed centrifugation (10,000 g). Virtually all of this apparently soluble topo II is particulate with a sedimentation coefficient of 67 S. Similar topo II-containing particles were detected in Drosophila Kc tissue culture cells, 16-19-h old embryos and extracts of progesterone-matured oocytes from Xenopus. Drosophila topo II-containing particles were insensitive to EDTA, Triton X-100 and DNase I, but could be disrupted by incubation with 0.3 M NaCl or RNase A. After either disruptive treatment, topo II sedimented at 9 S. topo II-containing particles were also sensitive to micrococcal nuclease. Results of chemical cross-linking corroborated those obtained by centrifugation. Immunoblot analyses demonstrated that topo II-containing particles lacked significant amounts of lamin, nuclear pore complex protein gp210, proliferating cell nuclear antigen, RNA polymerase II subunits, histones, coilin, and nucleolin. Northern blot analyses demonstrated that topo II-containing particles lacked U RNA. Thus, current data support the notion that nonnuclear Drosophila topo II-containing particles are composed largely of topo II and an unknown RNA molecule(s).
...
PMID:An RNase-sensitive particle containing Drosophila melanogaster DNA topoisomerase II. 808 68

We have studied the chromatin structure of the Saccharomyces cerevisiae FBP1 gene, which codes for fructose-1,6-bisphosphatase. A strong, constitutive, DNase I, micrococcal nuclease and S1 nuclease hypersensitive site is present close to the 3' end of the coding region. In the repressed state, positioned nucleosomes exist around this site, and subtle changes occur in this nucleosomal organization upon derepression. A DNase I hypersensitive region is located within the promoter between positions -540 and -400 and its extends towards the gene in the derepressed state, leading to an alteration of nucleosomal positioning. Psoralen crosslinking of chromatin, which is used for the first time to study the mobility of restriction fragments from an RNA polymerase II gene, revealed that part of the promoter is nucleosome-free, in accordance with the results of DNase I digestion. A model is presented that, based on the chromatin structure, puts forward the hypothesis that the promoter UAS is located between -540 and -340. Finally, psoralen crosslinking, as well as digestions with micrococcal nuclease or restriction endonucleases suggests that most if not all of the copies of the active FBP1 gene are covered by nucleosomes.
...
PMID:Chromatin structure of the yeast FBP1 gene: transcription-dependent changes in the regulatory and coding regions. 810 72

Sin4p is a component of a mediator complex associated with the C-terminal domain of RNA polymerase II and SIN4 is required for proper regulation of several genes in yeast, including the HO endonuclease gene, glucose repressible genes and MATa cell-specific genes. Previous studies indicated that SIN4 may influence transcription through changes in the organization of chromatin. We have examined a specific chromatin structure associated with MATa cell-specific repression in sin4 MATalpha cells to determine if SIN4 is required for nucleosome positioning. Although the loss of SIN4 has no effect on nucleosome location, we find that the sensitivity of bulk chromatin from sin4 cells to micrococcal nuclease digestion is strikingly increased relative to chromatin from isogenic wild-type cells. The nuclease hypersensitivity of chromatin from sin4 cells is not related to gross alterations in histone gene expression or to bulk increases in histone modification. Our experiments suggest that SIN4 directly or indirectly regulates a global aspect of chromatin accessibility, providing a molecular basis for phenotypic similarities between sin4 mutations and mutations in histones.
...
PMID:Global alterations in chromatin accessibility associated with loss of SIN4 function. 909 35


<< Previous 1 2 3 4 Next >>

---