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 solubility of adult beta-globin chromatin (beta A chromatin) from immature chicken red blood cells can be controlled by the presence or absence of n-butyrate in a cell incubation medium. In the absence of n-butyrate, only a small percentage (approximately 4%) of the total beta A chromatin is in a soluble chromatin fraction following micrococcal nuclease digestion and centrifugation. This percentage increases to approximately 40-45% of the beta A chromatin if cells are incubated 1 hour in the presence of 10 mM sodium n-butyrate. The highest yield and enrichment of solubilized beta A chromatin is attained when 1-4% of the DNA is rendered acid soluble, and in buffers containing 1.5 - 5 mM MgCl2. The soluble beta A nucleohistone is nucleosome oligomer size (contains DNA 250-600 bases in length) and can be separated from soluble, transcriptionally inert mononucleosomes by agarose A-5m exclusion chromatography. The enhanced solubility appears to be specific for transcriptionally active chromatin. Whereas 40-45% of the beta A chromatin is recovered in the supernatant fraction from n-butyrate incubated immature erythrocytes, nucleohistone containing ovalbumin DNA sequences remains insoluble.
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PMID:N-Butyrate incubation of immature chicken erythrocytes preferentially enhances the solubility of beta A chromatin. 400 Sep 50

The interaction between beta-globin RNA and proteins in chicken reticulocyte nuclei was studied by determining the sequence of nuclease-resistant beta-globin RNA. Two types of nuclease-resistant RNAs were isolated for this study: endogenous nuclease-resistant RNA from 50S heterogeneous nuclear RNA-protein complexes and micrococcal nuclease-resistant nuclear RNA from whole nuclei. The nuclease-resistant regions were identified with the use of a RNA mapping method we recently developed (J.R. Patton and C.-B. Chae, J. Biol. Chem. 258:3991-3995, 1983). We found that beta-globin RNA is assembled into heterogeneous nuclear RNA-protein complexes in a specific manner. There are several regions of nuclease resistance in the first and third exons interrupted at regular intervals by sensitive regions. The second exon has only one nuclease-resistant region. The resistant regions range in size from 20 to 50 nucleotides. This organization may reflect a specific mode of assembly for heterogeneous nuclear RNA-protein complexes.
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PMID:Specific regions of beta-globin RNA are resistant to nuclease digestion in RNA-protein complexes in chicken reticulocyte nuclei. 403 49

Chromatin generated by micrococcal nuclease digestion of erythrocyte nuclei can be fractionated into two pools of differing solubility in solvents containing 0.15-0.25 M NaCl. A fixed percentage of the chromatin is soluble under these conditions, independent of the average size of the DNA in the unfractionated chromatin. Chromatin containing particular gene sequences is also distributed between soluble and insoluble fractions in a way that is independent of the average size of the starting material. However, the actual percentage of gene copies present in each fraction is not necessarily the same as for bulk chromatin. The transcriptionally active chicken erythrocyte adult beta-globin gene is more soluble than the bulk, while the ovalbumin gene in the same tissue is less soluble. These differences do not appear to be related to variations in content of RNA, core histones, or two classes of non-histone proteins. Instead, we find that the soluble chromatin pool is somewhat depleted in histones H1 and H5 and contains lower molecular weight DNA than precipitable chromatin. The soluble fraction can be made insoluble by addition of H1. If the precipitable chromatin fraction is redigested to reduce its size and then recombined with the soluble fraction and reprecipitated, the distribution of globin gene is randomized. The results suggest that the partitioning of chromatin into soluble and insoluble pools in 0.15-0.25 M NaCl arises from redistribution of a limiting amount of histones H1 and H5 to the chromatin fractions containing the longest DNA.
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PMID:Solubility and structure of domains of chicken erythrocyte chromatin containing transcriptionally competent and inactive genes. 409 99

Active genes are known to have an altered chromatin structure that is preferentially sensitive to digestion with DNAase I. We find that when chicken red blood cells are incubated in media containing the topoisomerase II inhibitor novobiocin, the preferential DNAase I sensitivity of the active beta-globin genes is reversed in vivo with as little as 20 min of drug treatment. Control experiments suggest that inhibition of a topoisomerase II is responsible for this alteration in active gene conformation. Reversal of DNAase I sensitivity can also be induced in vitro by partial cleavage of the nuclear DNA with staphylococcal nuclease. We propose that the altered structure around active genes is maintained by continuous DNA supercoiling and that in the absence of this superhelical tension active chromatin reverts to a less DNAase I-sensitive ground state.
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PMID:Torsional stress promotes the DNAase I sensitivity of active genes. 609 6

Adult beta-globin gene chromatin in murine erythroleukemia (MEL) cells acquired increased sensitivity to both micrococcal nuclease and DNase I during hexamethylenebisacetamide-induced erythoid differentiation. The DNase I hypersensitivity of the globin genes accompanied their actual transcription and was strongly correlated with commitment events. On the other hand, the rate of micrococcal nuclease digestion was closely related to the rate of globin gene transcription. Two distinct DNase I hypersensitive sites were found on the 5' side of the beta-major globin gene in HMBA-induced cells. One site was located near the 5' side of the beta-major globin gene and the second site was located approximately 3 kilobases upstream of the beta-major cap site. Following the commitment of MEL cells to differentiate, DNase I sensitivity was stably inherited in the absence of inducer. In contrast to HMBA, another inducer, hemin, known to cause the accumulation of globin-specific mRNA in MEL cells by a post-transcriptional mechanism, did not elicit alterations of beta-globin gene chromatin. The addition of dexamethasone, a hormone known to inhibit MEL cell commitment, blocked the formation of general and site-specific nuclease sensitivity of beta-globin gene chromatin prior to but not after cell commitment.
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PMID:Alterations in globin gene chromatin conformation during murine erythroleukemia cell differentiation. 623 Dec 95

We have analyzed the chromatin structure of the beta-major globin gene and other related beta-globin genes in induced and uninduced murine erythroleukemia (MEL) cell nuclei. Nuclei were digested with either DNase I or micrococcal nuclease, and the purified DNA was hybridized to a set of cloned genomic DNA fragments covering the beta-globin gene region. This region consisted of two distinct domains as characterized by sensitivity to DNase I digestion. One domain was relatively sensitive and contained the potentially active or actively transcribed beta-major and beta-minor globin genes. The other, relatively insensitive domain contained the nontranscribed embryonic and beta-globin homologous genes. The sensitivity of these domains was not altered during erythroid differentiation. In nonerythroid cells, the entire globin gene family, including the adult and embryonic globin genes, was contained in a single relatively resistant domain. Micrococcal nuclease (MNase) also defined two general domains of nuclease sensitivity that coincided with those of DNase I. However, the relatively sensitive MNase domain containing the beta-major and beta-minor genes became more sensitive upon chemically stimulated erythroid differentiation. A detailed examination of the beta-major globin gene revealed that the actual coding region became increasingly sensitive to micrococcal nuclease after differentiation while the 5'-flanking DNA did not. Thus, micrococcal nuclease was able to accurately define the primary transcription unit of the beta-major gene.
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PMID:Chromatin structure of the beta-globin gene family in murine erythroleukemia cells. 623 52

We have monitored the differential nuclease sensitivity of defined regions of the chicken genome in different cells using a method which combines restriction enzyme digestion and blotting to diazobenzyloxymethyl (DBM)-paper (see Ref. 11). By using different specific probes and by scanning the bands on the autoradiograms, it is possible to compare on the same blot the digestion patterns of similar-sized fragments from different regions of the genome corresponding to "active" and reference "inactive" genes. We have demonstrated the preferential sensitivity to DNaseI and micrococcal nuclease digestion of the ovalbumin gene region in hen oviduct chromatin. The beta-globin gene region (containing both an adult and an embryonic gene) is also preferentially digested by DNaseI in hen mature erythrocyte nuclei, but at a lower rate than the ovalbumin gene region in oviduct. These observations raise the possibility that there may be several types of preferential nuclease sensitivities, all characterized by increased rates of digestion but to different levels, the highest corresponding to the very actively transcribing genes.
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PMID:Differential nuclease sensitivity of the ovalbumin and beta-globin chromatin regions in erythrocytes and oviduct cells of laying hen. 625 91

We have examined in some detail the chromatin structure of a 6.2 kilobase pair (kbp) chromosomal region containing the chicken beta-globin gene. The chromatin structure was probed with three nucleases, DNase I, micrococcal nuclease, and DNase II, and the rate of digestion of specific subfragments of the region was compared with the rate of bulk DNA digestion. We have characterized the rate of digestion of each fragment in terms of a sensitivity factor which measures the sensitivity of a fragment to a particular nuclease relative to bulk DNA. The sensitivity factors were determined by a least squares curve fitting method based on target analysis. In nuclei isolated from 14-day-old chicken embryo red blood cells, the entire 6.2-kbp region shows approximately a 10- to 20-fold increase in sensitivity to DNase I, a 3-fold increased sensitivity to micrococcal nuclease, and a 6-fold increased sensitivity to DNase II. In addition to the adult beta-globin gene, this region contains 5' and 3' flanking sequences, the 5' half of the inactive, embryonic globin gene, epsilon, and some repeated sequences. There is no obvious correlation between these genetic elements and the overall chromatin structure as measured by the nuclease sensitivity. This same region shows little or no special sensitivity in nuclei isolated from 14-day-old chicken embryo brain. Furthermore, fragments of the inactive ovalbumin gene show little or no sensitivity in either red blood cells or brain. These results support the conclusion that the entire 6.2-kbp region is largely packaged as active chromatin in 14-day-old chicken embryo red blood cells.
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PMID:Chromatin structure of the chicken beta-globin gene region. Sensitivity to DNase I, micrococcal nuclease, and DNase II. 628 52

Brief micrococcal nuclease digestion of chick embryonic red blood cells results in preferential excision and solubilization of monomer nucleosomes associated with beta-globin sequences and also 5'-sequences flanking the beta-globin gene. Both regions are DNAse-I sensitive in nuclei. Such salt-soluble nucleosomes are enriched in all four major HMG proteins but HMG1 and 2 are only weakly associated. These nucleosomes appear to have lost much of the DNAse-I sensitivity of active genes. The HMG14 and 17-containing salt-soluble nucleosomes separated by electrophoresis are not DNAse-I sensitive and contain inactive gene sequences as well as active sequences. Reconstitution of HMG proteins onto bulk nucleosomes or chromatin failed to reveal an HMG-dependent sensitivity of active genes as assayed by dot-blot hybridization and it was found that the DNAse-I sensitivity of ASV proviral sequences as assayed by dot-blot hybridization was not HMG-dependent. These results indicate that higher order chromatin structures might be responsible for nuclease sensitivity of active genes.
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PMID:The nuclease sensitivity of active genes. 630 Jul 66

The pattern of sites within purified DNA that are highly susceptible to double-stranded cleavage by micrococcal nuclease has been analyzed in the vicinity of over 20 genes from widely separated loci in Drosophila. These genes have uniformly exhibited a distinctive organization of cleavage sites such that at early times of digestion major sites are observed in the spacer regions surrounding the genes, but not within the protein coding regions themselves. Examples examined include Drosophila genes for heat-shock proteins, cytoplasmic actin, ribosomal protein 49, alcohol dehydrogenase, Sgs 4 glue protein, and other developmentally regulated transcripts, a human beta-globin gene, and mouse alpha 3-globin pseudogene. It seems probable that this gene/spacer pattern will be a general one in the genomes of eucaryotes, but not in the genomes of procaryotes, since neither pBR322 nor phage lambda DNA display such a pattern. One observes a nonrandom spacing of strong cleavage sites in Drosophila DNA, with the most frequent intervals being 195 bp and 411 bp. Such a pattern of variation in DNA structure may have evolved to facilitate the packaging of eucaryotic DNA into chromatin.
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PMID:Patterns of DNA structural polymorphism and their evolutionary implications. 631 4


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