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:1.11.1.7 (peroxidase)
65,474 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Methylation and DNase I-hypersensitive sites of the myeloperoxidase gene in human myeloid leukemia HL-60 cells were studied by Southern blot hybridization using the myeloperoxidase gene probes. Digestion of DNA with a methylation-sensitive restriction endonuclease indicated that a CpG in the CCGG sequence located 3.53 kbp upstream of the myeloperoxidase gene was unmethylated in HL-60 cells expressing the gene, whereas it was methylated in K562 cells and human placenta not expressing the gene. The site in HL-60 cells remained unmethylated after retinoic acid- or 12-O-tetradecanoyl-phorbol-13-acetate-induced differentiation that arrests myeloperoxidase synthesis. Digestion of isolated nuclei with various amounts of DNase I indicated that four DNase I-hypersensitive sites were in an upstream region of the myeloperoxidase gene in HL-60 cells and three sites were within the gene. In retinoic acid-induced cells, the bands of the hypersensitive site near the 5' side of the gene and that in the first intron became weak, while that of the site in the fifth intron became strong. The bands of these hypersensitive sites were weak in K562 cells. The implications of these changes in tissue-specific expression and developmental down-regulation of the myeloperoxidase gene are discussed.
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PMID:Undermethylation and DNase I hypersensitivity of myeloperoxidase gene in HL-60 cells before and after differentiation. 130 85

Expression of the myeloperoxidase (MPO) gene is tightly regulated in a tissue- and development-specific manner. Accumulation of MPO messenger RNA (mRNA) occurs only at the late myeloblastic and promyelocytic stages of myeloid differentiation and is negligible at other stages of myeloid development and in other tissues. The goal of our studies was to begin to understand the events that occur to control MPO gene expression during normal granulocytopoiesis. Chromatin structure of the MPO gene was evaluated by DNase I treatment of isolated nuclei and Southern blot analysis. No detectable DNase I hypersensitive sites were found in the region of the MPO gene in non-myeloid cells. One site was present in the 5' upstream region in myeloid cells that are developmentally too immature to transcribe MPO. Three sites of hypersensitivity in the regions of the putative MPO promoter and upstream region occurred in MPO-expressing promyelocytes. These sites were markedly reduced in terminally differentiated, non-expressing myeloid cells. Analysis of DNA methylation of the MPO gene using methylation-sensitive restriction enzymes showed that the gene was highly methylated in non-myeloid cells. Stepwise demethylation occurred in myeloid cells developmentally too immature to transcribe MPO. Maximal demethylation in the 5' gene region occurred in MPO-expressing promyelocytes. This methylation pattern did not change in terminally differentiated, MPO non-expressing myeloid cells. A somatic hybrid cell formed by fusion of HL-60 (MPO-expressing cells) and PUT (MPO non-expressing lymphoid cells) extinguished expression of MPO and showed a chimeric pattern of MPO gene methylation, suggesting that demethylation is necessary but not sufficient for expression of the MPO gene. Our studies show that demethylation and DNase I hypersensitivity of the MPO gene were associated with a tissue-dependent potential for MPO gene expression that preceded the developmental ability to express MPO mRNA.
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PMID:Changes of DNA methylation and chromatin structure in the human myeloperoxidase gene during myeloid differentiation. 164 80

The DNase I sensitivity of three different chromatin regions in mouse testicular cells was analysed by in situ nick translation with biotin-dUTP combined with various counterstaining techniques. The regions were: (i) the constitutive centromeric heterochromatin, (ii) an interstitial C-band positive insertion on chromosome 1, Is(HSR1;C5)1Lub, and (iii) the chromatin containing rDNA (designated nucleolar chromatin herein). Incorporated biotin was detected either by the horseradish peroxidase reaction with diaminobenzidine (DAB) or the alkaline phosphatase reaction with fast red. The latter resulted in a water insoluble red precipitate, which was easily removable by any organic solution thus allowing the application of various counterstaining protocols. DNase I sensitivity of the three chromatin regions was screened in different cell types of the mouse testis. The interstitial Is(HSR) region was highly DNase I sensitive when it was recognizable by strong mithramycin fluorescence. The centromeric heterochromatin was DNase I resistant when it was compacted into microscopically visible chromosomal structures (mitosis, pachytene, metaphase I and II). In interphase nuclei from Sertoli cells and spermatogonia it became highly DNase I sensitive. In round spermatids it displayed medium DNase I sensitivity. Nucleolar chromatin was not labelled by in situ nick translation when silver staining demonstrated strong protein production. Sperm cells were highly DNase I sensitive from stages 11 to 15, but resistant as mature spermatozoa.
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PMID:Nonradioactive in situ nick translation combined with counterstaining: characterization of C-band and silver positive regions in mouse testicular cells. 169 89

The level of myeloperoxidase (MPO) mRNA is reduced significantly after HL-60 induced differentiation with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). We examined the chromatin structural changes of the MPO gene during TPA induction. Before TPA induction about nine DNase I hypersensitive sites (HS) were found on the 5' upstream and at various intron regions of the MPO gene. A new HS was found on intron 8 within 4 h of induction; its appearance preceded down regulation of the MPO gene. At the same time DNase I HS found in 0.3 and 1-1.5 kb upstream of the MPO CAP site, were significantly reduced or disappeared after TPA induction. These chromatin structural changes could be closely linked to the mechanism which regulates the MPO gene expression.
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PMID:Down regulation of myeloperoxidase gene associated with specific nuclease hypersensitive sites during TPA induced differentiation of HL-60. 184 1

In order to establish the presence of Z-DNA sequences in the normal crystalline lens and to define their structure-function relationship, fixed and unfixed calf lens tissue sections were examined immunohistochemically. Polyclonal and monoclonal anti-Z-DNA antibodies were developed as immunoprobes, using brominated (Br-) poly(dG-dC).poly(dG-dC) as an antigen. The structure of the Z-helix antigen was confirmed by circular dichroism (CD) and U.V. spectroscopy. Whole rabbit and goat anti-Z-DNA sera; rabbit and goat IgG polyclonal anti-Z-DNA antibodies; and anti-Z-DNA monoclonal IgG antibodies were utilized as Z-DNA immunoprobes to localize the Z-DNA in calf lens tissue sections. Immunohistochemical examination using the peroxidase-antiperoxidase (PAP) method indicated that the cortex region of the lens reacted strongly with the anti-Z-DNA antibodies, while no immunoreaction could be observed in the nucleus region. Similar immunoreactive patterns were obtained whether whole sera, affinity purified IgG polyclonal antibodies or monoclonal antibodies were utilized. Immunobinding of anti-Z-DNA antibodies was low, effectively background type binding, in unfixed lens tissue sections. Various fixatives were tested to explore the potential antibody-Z-DNA interaction in calf lens tissue. Nuclear fixatives enhanced Z-DNA antibody immunoreactivity, while formalin, microanatomic and cytoplasmic fixatives produced lesser results. Digestion of the lens tissue with DNase I eliminated Z-DNA immunoreactivity, while RNase A and RNase T1 treatment had no effect. Actinomycin D also prevented Z-DNA immunoreactivity.
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PMID:Fixation and immunolocalization of left-handed Z-DNA sequences in the calf lens. 195 42

To investigate the association of lipid with the cytoskeleton of platelets during aggregation, rabbit and human platelets were isolated and labeled with [3H]palmitic acid; lipid extraction showed approximately 80% in phospholipid. Limited aggregation was induced with ADP or thrombin, and the cytoskeleton was isolated after lysis with 1% Triton X-100, 5 mM EGTA. Cytoskeleton from unactivated platelets had approximately 0.03% of the total label in the platelets, but after aggregation with ADP (2 microM) or thrombin (0.1 U/ml) for 20-30 s, 1.5-8% of the label was with the cytoskeleton. Fibrinogen enhanced aggregation and the association of label with the cytoskeleton; incorporation of label increased exponentially as aggregation proceeded, decreased exponentially during deaggregation, and appeared to be related to the number of sites of contact. Inhibitors that increase cyclic AMP inhibited aggregation and cytoskeletal labeling, but aspirin had no effect. Some experiments were done with DNase I and Ca2+ in the Triton X-100 lysis medium to cause actin depolymerization, under conditions in which the Ca2+-dependent protease activity was inhibited. This greatly reduced the association of label with the cytoskeleton at early time points, but when aggregation had proceeded further, a large proportion of the label was not dissociated by this treatment. These findings, electron microscopy, and the enrichment of the cytoskeleton of aggregated platelets with only some of the membrane proteins that were labeled by the 125I-lactoperoxidase method, indicated that with limited aggregation, the 3H-labeled lipid was mainly associated with the cytoskeleton and not with trapped membrane fragments resulting from incomplete lysis. Since the pattern of cytoskeleton labeling ([3H]palmitate) and the selective association of some membrane proteins with the cytoskeleton/lipid complex was the same with ADP and thrombin, the reactions must be dependent on aggregation and not on events associated with the release of granule contents.
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PMID:Aggregation-related association of lipid with the cytoskeleton of rabbit and human platelets prelabeled with [3H]palmitic acid. Similar effects of adenosine diphosphate- and thrombin-induced aggregation. 282 26

Oval cells and biliary epithelial cells were isolated from livers of rats fed a choline-deficient diet containing 0.1% ethionine and from normal rat livers, respectively. Nonparenchymal cell suspensions prepared from these livers by collagenase perfusion followed by digestion of undissociated tissue with 0.1% collagenase, 0.1% Pronase, and 0.004% DNase I were separated into six fractions by centrifugal elutriation. Cells in each fraction were characterized histochemically for gamma-glutamyl transpeptidase, peroxidase, alkaline phosphatase, and glucose-6-phosphatase activities, and for albumin and alpha-fetoprotein by immunocytochemical methods. Cells from Fraction 5 of the elutriation procedure had various features predicted for oval cells and were selected for further studies. The cell yield in this fraction, from each preneoplastic liver, was 5.7 X 10(7) cells, 93 +/- 2% of which were gamma-glutamyl transpeptidase positive, 6 +/- 1% peroxidase positive, 61% albumin positive, and 29% alpha-fetoprotein positive. Cells in this fraction have a median diameter of 13.1 micron and are diploid and cycling. The majority of these cells has morphological features characteristic of biliary epithelial cells, although some cells display features intermediate between duct cells and hepatocytes. Nucleic acid hybridization using specific probes revealed that these cells contain albumin and alpha-fetoprotein messenger RNAs, while hepatocytes from normal and preneoplastic liver contain only albumin messenger RNA. Biliary cells obtained from normal livers do not contain albumin messenger RNA. The large-scale purification and characterization of cell populations from preneoplastic livers is an important step in elucidating the cellular derivation of liver tumors.
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PMID:Isolation of oval cells by centrifugal elutriation and comparison with other cell types purified from normal and preneoplastic livers. 669 43

Apoptosis is a type of physiologic cell death that occurs in many tissues and be regulated by peptide growth factors. Recent studies indicate that apoptosis occurs in the ovary during follicular atresia in several animal species, including the rat, pig, chicken, baboon, and rabbit. The purpose of this study was to demonstrate, through in situ identification of apoptotic cells in intact ovarian sections, the sites in which apoptosis occurs in the rat ovary in different functional states. We evaluated the presence of apoptosis in three models: immature rats, eCG-treated rats and adult cycling rats. Paraffin ovarian sections were pretreated with proteinase K and then end-labeled with biotinylated deoxyuridine triphosphate (dUTP) by incubation with the enzyme terminal deoxynucleotidyl transferase (TDT). They were then stained through use of avidin-conjugated peroxidase with 3,3'-diaminobenzidine as the substrate. Healthy antral and preantral follicles had no staining. The nuclei of granulosa cells of preantral and antral atretic follicles were positively stained in all the animal groups. Scattered theca cells were also stained. Stromal cells were consistently negative. Positive controls were sections pretreated with DNase I; these displayed intense staining of all nuclei. Negative controls, in which either terminal TDT or its biotinylated substrate was omitted, were appropriately negative. This study represents a systematic analysis of apoptosis in the rat ovary at different functional stages and supports the hypothesis that apoptosis is involved in the process of follicular atresia.
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PMID:In situ localization of apoptosis in the rat ovary during follicular atresia. 753 7

The molecular basis for commitment of progenitors to the eosinophil lineage and mechanisms by which eosinophil-specific genes are expressed and regulated during differentiation is unknown. Expression of eosinophil peroxidase (EPO) is restricted to the eosinophil lineage. To understand the mechanisms involved in transcriptional regulation of EPO gene expression, we clone the region of the EPO gene upstream of the transcriptional start site and analyzed the cis-acting elements required for EPO promoter activity in an eosinophil-inducible leukemic cell line, HL-60-C15. The 5'-flanking region of the EPO gene containing 1.5 kilobases of sequence upstream of the transcriptional start site was subcloned into the promoterless pXP2-luciferase vector. The EPO-pXP2 construct and 5' deletion mutants were electroporated into HL-60-C15 cells and luciferase reporter activity assessed. The -1.5-kilobase EPO-pXP2 promoter construct reproducibly expressed > 120-fold more luciferase activity than did promoterless pXP2, and a 12-fold (90%) decrease in promoter activity was obtained when sequences between -122 and -45 base pairs (bp) were deleted. The specificity of the EPO promoter for the eosinophil lineage was analyzed by transfecting the EPO-pXP2 constructs and deletion mutants into HL-60-C15 cells and the parental HL-60 line; EPO promoter activity was 8-10-fold less in the HL-60 parental line, suggesting lineage specific elements in the -122 to -45 bp region. To further characterize regulatory sequences important for promoter activity, we performed linker-scanning analysis on the -122 to -45 bp region and identified a number of positively and negatively acting elements in the promoter. DNase I footprinting was performed with HL-60-C15, HL-60, and HeLa nuclear extracts to identify nuclear proteins that may bind to the functional elements; these experiments identified three protected regions of the EPO promoter which correspond to the functional segments defined by linker-scanning analysis and which contain consensus, potential binding sites for Egr-1, H4TF-1, PuF, CTCF, UBP-1, and GaEII transcription factors. Further study of EPO promoter regulation should elucidate unique transcriptional features of eosinophil gene regulation in granulocyte development.
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PMID:Functional characterization of the promoter for the gene encoding human eosinophil peroxidase. 803 8

The myeloid-lineage specific enhancer at 3.4-3.1 kb upstream of the mouse myeloperoxidase gene [1] has been further characterised. In vitro DNase I footprinting experiments revealed three protected sequences (FT-I, -II and -III) in the enhancer, associated with the proteins that are enriched in WEHI 3BD+ cells, at which the MPO gene is highly expressed; but not in two non-MPO expressing lymphocytic cell lines. Site-specific mutations at each element severely reduced the level of the reporter gene activity in a non-additive manner. This is parallel with either abolishment or alteration of the corresponding wild-type protein-DNA interaction in vitro. Consideration of the sequence motifs present in the enhancer suggests that the cis-elements defined as the in vitro DNase I footprints are likely to be novel.
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PMID:The myeloid-lineage specific enhancer of the mouse myeloperoxidase gene consists of three cis-elements defined as in vitro DNase I footprints. 811 62


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