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11.
Identification and characterization of a novel repressor site in the human tumor necrosis factor alpha gene. 总被引:3,自引:0,他引:3
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In human monocytic cell lines, tumor necrosis factor alpha (TNF alpha) expression is induced by phorbol myristate acetate (PMA). We have identified positive and negative cis-acting elements in the TNF alpha promoter by deletion analysis. Here we present the initial characterization of the repressor element. The repressor element was shown to function in either orientation and at various distances upstream from the positive element of the TNF alpha promoter. The TNF alpha repressor site (TRS) has been localized to a 25 bp region between base pairs -254 and -230 in the promoter. This region contains a 10 bp sequence with homology to the binding site of the activator protein AP-2. Mutation of the 6 C's of this 10 bp AP-2-like site abolish TRS repressor function. However, this AP-2-like site is not a binding site for AP-2 protein based on gel retardation analysis. In addition, a well-characterized AP-2-binding site placed upstream of the positive element of the TNF alpha gene did not cause repression. Therefore, this repression is very likely mediated by a novel protein(s) which interacts with the AP-2 consensus site in the TRS. 相似文献
12.
A conserved helical element is essential for internal initiation of translation of hepatitis C virus RNA. 总被引:12,自引:5,他引:7
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Translation of hepatitis C virus (HCV) RNA is initiated by cap-independent internal ribosome binding to the 5' noncoding region (NCR). To identify the sequences and structural elements within the 5' NCR of HCV RNA that contribute to the initiation of translation, a series of point mutations was introduced within this sequence. Since the pyrimidine-rich tract is considered a characteristic feature of picornavirus internal ribosome entry site (IRES) elements, our mutational analysis focused on two putative pyrimidine tracts (Py-I and Py-II) within the HCV 5' NCR. Translational efficiency of these mutant RNAs was examined by in vitro translation and after RNA transfection into liver-derived cells. Mutational analysis of Py-I (nucleotides 120 to 130), supported by compensatory mutants, demonstrates that the primary sequence of this motif is not important but that a helical structural element associated with this region is critical for HCV IRES function. Mutations in Py-II (nucleotides 191 to 199) show that this motif is dispensable for IRES function as well. Thus, the pyrimidine-rich tract motif, which is considered as an essential element of the picornavirus IRES elements, does not appear to be a functional component of the HCV IRES. Further, the insertional mutagenesis study suggests a requirement for proper spacing between the initiator AUG and the upstream structures of the HCV IRES element for internal initiation of translation. 相似文献
13.
The role of polyamines (PA) synthesis in NMDA receptor-mediated45Ca2+ fluxes and norepinephrine release was studied in rat hippocampal synaptosomes. NMDA (50M) caused a sharp (>2-fold) transient increase in PA synthesis regulating enzyme, ornithine decarboxylase (ODC) activity with concomitant elevation in PA levels in the order putrescine>spermidine>spermine. ODC inhibitor, -difluoromethylornithine (DFMO), and NMDA antagonist, 2-amino-5-phosphonovaleric acid (D-AP5), both blocked increases in ODC activity and PA levels. Activation of NMDA receptors induced a sharp (3 to 4-fold) and quick (15 seconds) increase in45Ca2+ uptake by synaptosomes within 15 seconds of exposure at 37°C. The efflux of45Ca2+ and3H-norepinephrine (NE) release at 22°C from pre-loaded synaptosomes was also significantly (2 to 4-fold) enhanced by NMDA within 15 seconds. These NMDA receptor-mediated effects on calcium fluxes and NE release were blocked by NMDA receptor-antagonists (DAP-5 and MK-801) and PA synthesis inhibitor, DFMO and the DFMO inhibition nullified by exogenous putrescine. These observations establish that ODC/PA cascade play an important role in transduction of excitatory amino acid mediated signals at NMDA receptors.Special issue dedicated to Dr. Sidney Ochs. 相似文献
14.
Dipanwita Bhattacharya T.K. Dhar K.A.I. Siddiqui E. Ali 《Journal of applied microbiology》1994,77(2):129-133
The production of phaseolinone, a phytotoxic metabolite of Macrophomina phaseolina in infected Phaseolus mungo seeds grown on soil, was estimated by enzyme-linked immunosorbent assay and HPLC. The degree of inhibition of seed germination correlated well with the amount of toxin produced; 50% inhibition was observed at a toxin level of 2.1 μg g-1 of wet tissue. A comparison of the toxin-producing ability of nine isolates of the fungus obtained from different hosts and localities showed that the strain MPK'83 produced a significantly larger amount of the toxin, both in liquid culture and in infected seeds. The virulence of the isolates was related to their ability to produce phaseolinone. 相似文献
15.
Hamid Rashid Mohammad Najmus Saqib Abdul Aala Rajoka Muhammad Ibrahim Siddiqui Khawar Sohail 《Biotechnology Techniques》1997,11(4):245-248
A simple, sensitive, accurate and more informative assay for determining the number of modified groups during the course of carboxyl group modification is described. Monomeric carboxymethylcellulase (CMCase) from Aspergillus niger was modified by 1-ethyl-3(3-dimethylaminopropyl)carbodiimide (EDC) in the presence of glycinamide. The different time-course aliquots were subjected to non-denaturing PAGE and the gel stained for CMCase activity. The number of carboxyl groups modified are directly read from the ladder of the enzyme bands developed at given time. This method showed that after 75 min of modification reaction there were five major species of modified CMCases in which 6 to 10 carboxyls were modified. 相似文献
16.
Summary Primary and passaged cultures of normal colon epithelial cells, derived from human fetuses (13 to 17 wk of conceptual age)
have been established. These cultures have been passaged 16 times thus far. The cultures have been initiated and maintained
in medium consisting of 50% Dulbecco's minimum essential medium and 50% Ham's F12 medium and supplemented with antibiotics
(penicillin, 100 U/ml; streptomycin, 100 μg/ml); ascorbic acid, 40 μg/ml;l-isoleucine, 50 μg/ml; epidermal growth factor, 20 ng/ml; insulin, 5 μg/ml; cholera toxin, 5 ng/ml; transferrin, 1 μg/ml;
fetal bovine serum (10%); and HEPES, 25 mM final concentration, and incubated at 37°C in humidified gas containing 5% CO2: 95% air.
The cellular and subcellular characteristics of primary and passaged cultures were defined using light microscopy and scanning
and transmission electron microscopy. The cells exhibited microvilli on cell surfaces and showed junctional complexes and
interdigitations between cells. Indented nuclei with dense chromatin and marginated heterochromatin, numerous mitochondria,
rough endoplasmic reticulum, polysomes, and extensive Golgi zones were conspicuous. Also, periodic acid Schiff's reagent-positive
staining of the cells suggests the active synthesis of complex mucopolysaccharides in the cytoplasm.
This study was supported by USPHS Grant CA-30185 from the National Large Bowel Cancer Project, National Cancer Institute. 相似文献
17.
The skeletal muscle of Ophicephalus punctatus contains nine essential free amino acids, arginine, histidine, isoleucine, leucine, methionine, phenylalanine, threonine, valine and lysine, and eight non-essential amino acids, alanine, aspartic acid, cystine, glutamic acid, glycine, tyrosine, proline and serine. Histidine and lysine dominated the free amino acids pool. Seasonal variation was detected in the levels of histidine, arginine, leucine, phenylalanine, glycine, cystine and serine with highest values occurring in April and again in November. Changes were also detected in the concentrations of certain amino acids as the fish grew in size. Levels of free amino acids did not significantly differ between sexes. Factors effecting variation are discussed. 相似文献
18.
Reproductive biology, length-weight relationship and relative condition of Tilapia leucosticta (Trewavas) in Lake Naivasha, Kenya 总被引:1,自引:0,他引:1
In Lake Naivasha Tilapia leucosticta (Trewavas) spawns throughout the year. Males attain maturity at 180 mm and females at 160 mm total length. Males predominate over females in the catches (sex ratio 1-00 : 0-51). Fecundity ranged from 320 to 1328 eggs with an average of 751. The relationship between fecundity (F) and total length (L), body weight (W) and gonad weight (GW) is:
The length-weight regression coefficient is near to the cube. There is little seasonal fluctuation in relative condition of the fishes. 相似文献
The length-weight regression coefficient is near to the cube. There is little seasonal fluctuation in relative condition of the fishes. 相似文献
19.
A. H. Nagy Dr. M. O. Siddiqui Z. G. Kocsis G. Vida 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1980,57(4):75-78
Summary Two allelic forms of NAD specific malate dehydrogenase were found in samples of a wild population of Corydalis solida. The dimeric nature and the origin of the heterodimeric form has been demonstrated by in vitro dissociation and recombination of the subunits detected by subsequent electrophoresis. The method is applicable for polyacrylamide gel electrophoresis of crude leaf extracts of individual MDH isozyme forms. 相似文献
20.
A solid-phase immunoadsorbent specific for terminal deoxynucleotidyl transferase has been prepared. The enzyme from calf thymus and acute lymphoblastic leukemia cells binds to columns of this material. Bound enzyme can be eluted in an active form. Selective and rapid purification of terminal deoxynucleotidyl transferase from crude extracts of cells containing this enzyme can be achieved by this method since the immunoadsorbent has no affinity for other cellular DNA polymerases. 相似文献