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:3.2.1.17 (lysozyme)
21,489 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

New mutants of bacteriophage T4 that overproduce the enzyme dihydrofolate reductase were investigated. Unlike previously described overproducers of this enzyme (Johnson and Hall, 1974), these mutants did not overproduce deoxycytidylate deaminase. Overproduction of dihydrofolate reductase by the new mutants occurred because enzymatic activity continued to increase for a longer period of time in cells infected by the mutants than in cells infected by wild-type phage. This continued increase occurred even in the presence of rifampin, indicating that the overproduction is probably due to a post-transcriptional event. Both these new overproducers and the previously described overproducers were studied by using polyacrylamide gel electrophoresis. The two types of overproducers appeared to be very different. The previously described overproducers showed a delay and/or reduction in the synthesis of several proteins that normally started to be made 4 to 6 min after infection. Several proteins could be seen to be overproduced on the gels. The new overproducers did not show the delay in the synthesis of some proteins and only overproduced a few proteins. The new gene defined by the new overproducers is between the gene coding for thymidine kinase and the gene coding for lysozyme.
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PMID:Characterization of new regulatory mutants of bacteriophage T4. II. New class of mutants. 109 Jul 53

Identification of transcription factors regulating tissue-specific gene expression implies functional tests in transcription systems. In spite of its practical advantages, the Xenopus oocyte has only rarely been used for trans-activation studies, because some critical parameters inherent to the system may cause artefacts. Depending on the amount of DNA injected, even tissue-specific genes may be spontaneously transcribed. To develop a reliable trans-activation assay, we used the erythroid-specific rabbit beta-globin gene and, for comparison, the constitutively transcribed viral thymidine kinase gene. The viral gene is active over a wide range of injected DNA (0.2-10 ng), and addition of nuclear proteins from various cell types does not stimulate but often inhibits this activity. When large amounts of DNA are injected (greater than 10 ng), transcription is inhibited by self competition. Addition of nuclear proteins now re-establishes activity probably through increasing the pool of general transcription factors. By contrast, spontaneous activity of the beta-globin promoter occurs only within a narrow range of injected DNA (0.2-1 ng). At higher DNA concentrations (greater than 5 ng) spontaneous transcription becomes negligible. The addition of nuclear proteins from nonerythroid cells extracts has no or only a weak stimulatory effect on the beta-globin promoter. Only nuclear proteins isolated from erythroid tissues, bone marrow and spleen, bring about a strong transcriptional activation. Co-injection with either the polyoma virus, or the oviduct-specific chicken lysozyme gene shows that the beta-globin promoter is selectively activated by factors present in erythroid cell extracts.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Tissue-specific trans-activation of the rabbit beta-globin promoter in Xenopus oocytes. 225 41

Matrix attachment regions (MARs) are DNA elements that dissect the genome into topologically separated domains by binding to a chromosomal skeleton. This study explored the putative influence of the MAR located 5' of the chicken lysozyme gene on expression of heterologous genes in heterologous cell systems. Expression of a construct with the chloramphenicol acetyltransferase (CAT) indicator gene controlled by the herpes simplex virus thymidine kinase promoter (TC) and a construct in which the same transcriptional unit is flanked by chicken lysozyme 5' MARs (MTCM) was assayed after stable transfection into rat fibroblasts. Median CAT activity per copy number in MTCM transfectants was elevated approximately 10-fold relative to that in TC transfectants. Total variation in normalized CAT activity decreased from more than 100-fold among TC transfectants to nearly 6-fold among MTCM transfectants. The steady-state level of transcripts and the relative rate of transcription were increased in MTCM transfectants, as shown by S1 nuclease and run-on transcription assays, respectively. The chicken lysozyme 5' MAR thus can confer elevated, less position-dependent expression on a heterologous promoter in cells of a different species by increasing the density of transcribing RNA polymerase molecules. MAR-mediated transcriptional enhancement suggests that MARs are important for gene expression and not just for DNA packaging.
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PMID:The chicken lysozyme 5' matrix attachment region increases transcription from a heterologous promoter in heterologous cells and dampens position effects on the expression of transfected genes. 232 53

Vimentin is one member of the intermediate filament multigene family which exhibits both tissue- and developmental stage-specific expression. In vivo, vimentin is expressed in cells of mesenchymal origin. Previously, we identified both enhancer and promoter elements in the chicken vimentin gene which regulate gene expression in a positive manner. In this report, we have identified a 40-base-pair region at -568 base pairs between the proximal and distal enhancer elements which represses transcriptional activity. This silencer region can also repress the heterologous herpes simplex virus thymidine kinase promoter, which is comparable to the vimentin promoter. In addition, the element is able to function in a position- and orientation-independent manner, and the amount of repression is increased by multiple copies. Here we show by gel retardation assays and DNase I footprinting that this region binds a protein in nuclear extracts from HeLa cells. Southwestern (DNA-protein) blot analysis indicates this protein is approximately 95 kilodaltons in size. Moreover, protein distribution and activity mimic the expression pattern of vimentin during myogenesis, i.e., protein binding increases as vimentin gene expression decreases. The silencer region shares strong sequence similarity with 5'-flanking sequences found in both the human and hamster vimentin genes and with other characterized silencer elements, including the human immunodeficiency virus long terminal repeat, rat growth hormone, chicken lysozyme, and rat insulin genes. Thus, a negative element appears to bind a 95-kilodalton protein involved in regulating the tissue-specific expression of the chicken vimentin gene.
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PMID:A negative element involved in vimentin gene expression. 232 56

The chicken lysozyme gene is constitutively active in macrophages and under the control of steroid hormones in the oviduct. To investigate which DNA elements are involved in the control of its expression in macrophages we performed transient DNA transfer experiments with two different types of plasmids: 5'-deletion mutants of the upstream region of the chicken lysozyme gene and different fragments from this area in front of the thymidine kinase promoter (herpes simplex virus), each placed in front of the CAT (chloramphenicol acetyl transferase) coding sequence. Two enhancers (E-2.7 kb and E-0.2 kb) were characterized. They are active in macrophages, but not in chicken fibroblasts. Furthermore a negative element (N-2.4 kb) was identified, which is active in fibroblasts and promyelocytes, but not in mature macrophages. The combined action of all three elements contributes to the observed lysozyme gene activities: no activity in fibroblasts, moderate activity in promyelocytes and high activity in mature macrophages.
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PMID:Lysozyme gene activity in chicken macrophages is controlled by positive and negative regulatory elements. 358 88

Cloned complementary DNAs encoding chicken ovalbumin, chicken prelysozyme and calf preprochymosin, prochymosin and chymosin were inserted downstream from various viral promoters in modified recombinant "shuttle" vectors. Microinjection of the ovalbumin, prelysozyme and preprochymosin constructs into the nuclei of Xenopus laevis oocytes resulted in the synthesis, segregation in membranes and secretion into the extracellular medium of ovalbumin, lysozyme and prochymosin, respectively. Judging from molecular weight estimations, lysozyme and prochymosin were correctly proteolytically processed while ovalbumin, which lacks a cleavable signal sequence, was glycosylated. Injection of the DNA construct encoding prochymosin without its signal sequence resulted in synthesis of prochymosin protein that was localized exclusively in the oocyte cytoplasm. No immunospecific protein was detected after injection of the DNA encoding mature chymosin. In terms of protein expression in oocytes, the Herpes simplex thymidine kinase (TK) promoter was up to sevenfold more effective than the simian virus 40 (SV40) early promoter, and equally as effective as the Moloney murine sarcoma virus long terminal repeat element. Where tested, protein expression in oocytes was much reduced if DNA sequences encoding the SV40 small t intron and its flanking sequences were present in the constructs. S1 nuclease mapping of transcripts produced after injection of DNAs containing the TK promoter indicated that the majority of transcripts initiated at, or within, two bases of the known "cap" site. However, minor transcripts initiating upstream from this site were observed and one (or more) of these transcripts was responsible for the synthesis of an ovalbumin polypeptide containing a 51 amino acid N-terminal extension. This extended protein remained in the oocyte cytosol. When ovalbumin cDNA was inserted into the vectors with opposite polarity to the viral promoter, expression in oocytes resulted in the predominant synthesis and secretion of a variant ovalbumin with a 21 amino acid N-terminal extension, although some full-length ovalbumin was also synthesized and secreted. S1 mapping revealed the presence, in these oocytes, of transcripts of predicted polarity initiating 118 bases upstream from the wild type ovalbumin initiator ATG, at a previously unreported SV40 "promoter". No protein synthesis was detected after the injection of these reverse-orientation constructs into baby hamster kidney (BHK-21) cells.
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PMID:Efficient expression of cloned complementary DNAs for secretory proteins after injection into Xenopus oocytes. 609 86

Biochemical markers of multiple myeloma (MM) including beta 2-microglobulin (beta 2MG), C-reactive protein, neopterin, fibronectin, lactate dehydrogenase (LDH), thymidine kinase, connective tissue components, osteocalcin, amylase, etc. are reviewed. To date, no reliable biochemical markers have been reported for the diagnosis of MM. beta 2MG and LDH are widely used to predict the prognosis of the patients with MM. The value of other parameters is however, controversial. The cytochemical diagnosis of MM, using acid phosphatase, beta-glucronidase and lysozyme are also mentioned. Furthermore, the significance of the assay of various hormones, ammonia, cobalamin and electrolytes in MM are discussed.
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PMID:[Biochemical markers of multiple myeloma]. 769 95

The protoplast fusion technique of Schaffner (W. Schaffner, Proc. Natl. Acad. Sci. U.S.A. 77:2163-2167, 1980) has been adapted to introduce cloned herpes simplex virus genes into cultured mammalian cells. The technique involves digesting bacterial cell walls with lysozyme to produce protoplasts and then fusing the protoplasts to mammalian cells by treatment with polyethylene glycol. For monitoring transfer, protoplasts were labeled with the fluorescent dye fluorescein isothiocyanate before fusion. After fusion, greater than 50% of the mammalian cells were fluorescent, demonstrating that bacterial material was transferred with high frequency. Transfer of plasmid pBR325 occurred at frequencies of 1 to 2%, as measured by in situ hybridization. Fusion transfer of a chimeric plasmid consisting of the herpes simplex virus type 1 (strain KOS) EcoRI fragment F in pBR325 resulted in expression of some viral genomic sequences in about 5% of the mammalian cells, as detected by indirect immunofluorescence. One Ltk- cell in 300 to 500 was transformed to the TK+ phenotype after fusion with protoplasts carrying the chimeric plasmid pX1, which consists of pBR322 and the BamHI fragment coding for the herpes simplex virus type 1 thymidine kinase gene.
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PMID:High-frequency transfer of cloned herpes simplex virus type 1 sequences to mammalian cells by protoplast fusion. 927 87

Alterations in histone acetylation status appear to play a central role in the regulation of neoplasia, tumor suppression, cell cycle control, hormone responsiveness and senescence. These alterations of chromatin control gene transcription. The histone acetylation status is regulated by the equilibrium of histone acetyl-transferase activity (HAT) and the histone deacetylase activity (HDAC). Commonly, DNA-transfection assays are used to measure the effect of histone acetylation and deacetylation on gene transcription. Here we have analyzed the response of various viral long terminal repeats and vertebrate promoters to the specific histone deacetylase inhibitor trichostatin A (TSA). We show that the activity of many, but not all, promoters is increased upon TSA treatment. Interestingly, the lysozyme promoter exhibited TSA resistance, while the activity of metallothionine, the human growth hormone, and the thymidine kinase promoters was increased. Furthermore, we found that all tested viral promoters are induced by TSA. Analysis of the transcriptional behaviour of the thyroid hormone receptor (TR), the cellular homologue of the v-erbA oncogene, revealed that TSA reduced the gene silencing function but had no influence on the hormone-induced gene activation function of the receptor. These results on gene specific effects, together with the HDAC structural data (1), may be a basis for the development of HDAC inhibitors as antitumor agents.
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PMID:Promoter specific sensitivity to inhibition of histone deacetylases: implications for hormonal gene control, cellular differentiation and cancer. 1081 Mar 90

Since the transcription factor Zfhep is expressed in somatotropes and binds the rat growth hormone (rGH) gene T3-response element (TRE), we investigated whether Zfhep regulates the response of this gene to T3. In cotransfection experiments, Zfhep did not regulate the native rGH promoter in the absence of T3. However, Zfhep repressed T3-mediated activation significantly in either GH(3) or JEG-3 cells. Up to 70% repression was mediated through the rGH TRE in a heterologous promoter (thymidine kinase), but was not observed with the idealized DR4 or chicken lysozyme F2 TREs. Zfhep apparently does not repress T3-mediated activation simply by competition for binding to DNA since the C-terminal DNA-binding domain of Zfhep (which is sufficient for DNA-binding) is not sufficient for repression and since cotransfection of excess thyroid hormone receptor (TR) did not prevent repression by Zfhep. These data indicate that the rGH TRE is a composite element that can integrate Zfhep and T3 regulation.
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PMID:T3-activation of the rat growth hormone gene is inhibited by a zinc finger/homeodomain protein. 1147 47


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