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At least 703 records · Page 39Linked to original sources
PubMed1987

Involvement of prostaglandin E2 in bile acid-caused promotion of colon carcinogenesis and anti-promotion by the cyclooxygenase inhibitor indomethacin.

The mechanism of the anti-promoting effect of the prostaglandin (PG) synthesis inhibitor indomethacin in colon carcinogenesis was investigated. Male Sprague-Dawley rats received 0.002% water solution of indomethacin as drinking water freely for 3 days, then a subcutaneous injection of various doses of PGE2 and/or an intrarectal instillation of 12 mumol of sodium deoxycholate as a colon tumor promoter. Ornithine decarboxylase (ODC), a marker of tumor promotion, in the distal colonic mucosa was assayed at 4 hr after deoxycholate instillation. Indomethacin significantly suppressed the deoxycholate-augmented increase of ODC activity, while exogenous PGE2 restored or further increased the augmented ODC activity. The amount of PGE2 and the level of ODC activity were well correlated. However, PGE2 alone without deoxycholate did not increase the activity. Deoxycholate markedly increased colonic mucosal PGE2 at 1 hr after the instillation, and indomethacin decreased it. The results indicate that PGE2, the production of which is stimulated in the colonic mucosa by deoxycholate, is involved in the induction of colonic mucosal ODC. This is probably why PG synthesis inhibitors may inhibit the tumor promotion and prevent cancer development in the colon.

Administration, Oral↗
PubMed1988

Four-day duration of tumor promoter exposure required to transform JB6 promotion-sensitive cells to anchorage independence.

The JB6 mouse epidermal cell lines have been developed to study promotion of neoplastic transformation in vitro. Treatment of JB6 cells with 12-O-tetradecanoylphorbol-13-acetate (TPA) at 1 to 100 ng/ml results in the irreversible acquisition of tumorigenicity in nude mice and anchorage-independent growth. Among the biochemical responses which occur during TPA treatment is a decrease in procollagen synthesis. During a study of the possible role of H2O2 in the process of promotion, it was observed that catalase purchased commercially would inhibit TPA promotion as well as the reduction of collagen synthesis in a dose-dependent manner. A highly purified catalase preparation failed to demonstrate the TPA blocking activity, suggesting that this activity was due to a contaminating factor. We have separated the TPA blocking factor from the catalase itself using concanavalin A affinity chromatography. The factor is a Mr 60,000 glycoprotein showing TPA hydrolase activity. The enzyme, which is similar to a murine liver-derived TPA hydrolase, produces a single phorbol product from TPA that has been identified as phorbol-13-acetate. TPA hydrolase was used to terminate TPA action in soft agar. This made it possible to establish that approximately 4 days of exposure to phorbol esters are required for promotion of transformation in the JB6 model system.

Animals↗
PubMed1983

Inhibition of mouse skin tumor promotion and of promoter-stimulated epidermal polyamine biosynthesis by alpha-difluoromethylornithine.

Application of the tumor-promoting agent 12-O-tetradecanoylphorbol-13-acetate (TPA) to mouse skin leads to a manifold induction of ornithine decarboxylase (ODC) activity within 5 hr and an increased accumulation of putrescine. The relevance of these TPA-induced changes to the mechanism of tumor promotion was investigated using alpha-difluoromethylornithine (DFMO), an irreversible inhibitor of ODC. DFMO applied to mouse skin (0.3 mg in 0.2 ml of solvent) or administered in the drinking water (1%) in conjunction with skin tumor promotion by TPA inhibited the formation of mouse skin papillomas by 50 and 90%, respectively. TPA-induced ODC activity and the accumulation of putrescine were almost completely inhibited. DFMO given in the drinking water decreased spermidine levels, but DFMO treatment by any route did not alter the spermine levels of mouse epidermis. DFMO decreased TPA-induced hyperplasia by 25 to 40%, and the TPA-caused increases in DNA synthesis and mitotic index were inhibited by 60 and 50%, respectively. Therefore, in mouse epidermis, enhanced cell proliferation can be dissociated from ODC induction and the accumulation of putrescine. At the tested dose levels and routes of administration, DFMO did not inhibit the inflammatory response to TPA in several tissues. These results provide evidence for an essential role of ODC induction and the accumulation of putrescine in tumor promotion by TPA and add strength to the proposal that DFMO may be a promising drug for the prevention and treatment of cancer in human beings.

Adenosylmethionine Decarboxylase↗
PubMed1980

Promotion of benign hyperplastic lesions in hamster cheek pouch by membrane labilizing agents and calcium ion: evidence that intracellular calcium-induced release from growth control is an obligatory preliminary stage of tumor promotion.

Ca ion, ionophore 23187 and the membrane labilizing agents triton X-100, trypsin and phospholipase C promoted benign hyperplastic lesions (BHLs) but only rarely advanced tumors in hamster cheek pouch mucosa, which had been initiated with 7,12 dimethylbenz (a) anthracene. Retinyl acetate (RA) and croton oil markedly promoted both BHLs and advanced tumors. These results suggest that pathways modulated by intracellular Ca cause initiation-stabilized release from growth control, thus the promotion of BHLs, whereas additional mechanisms are required for the progression of BHLs to more advanced tumors. Some Ca-modulated systems which could be involved in promotion of BHLs are discussed in the light of published literature.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2004

Second-generation tetracycline-regulatable promoter: repositioned tet operator elements optimize transactivator synergy while shorter minimal promoter offers tight basal leakiness.

BACKGROUND: The tetracycline-regulatable system is one of the most valuable tools for controlling gene expression. In its current form, however, the system is less than ideal for in vivo or gene therapy uses due to difficulties in set-up procedures, high basal leakiness, and unpredictable delivery and efficiency. METHODS: To address these issues, we have devised a second generation of tetracycline-regulated promoters (TREs). The second-generation TRE (SG-TRE) contains a shortened cytomegalovirus (CMV) minimal promoter together with eight tet operator sequences positioned in an optimized manner upstream of the TATA box. This construct displays far greater reduction in basal leakiness than maximal transgene expression. Conversely, maximal transgene expression is increased to a greater degree than basal leakiness by post-translational stabilization with bovine growth hormone poly A. RESULTS: In transient studies, the SG-TRE displays over 100 000-fold regulation efficiency in HeLa cells at 1:1 ratio of transactivator to reporter plasmid in the Tet-Off system. This novel promoter achieves a regulation efficiency 500- to 1000-fold higher than that of the original TRE (P(hCMV*-1)) in HeLa cells by displaying undetectable levels of basal leakiness without compromised maximal expression. In other cell lines, the SG-TRE proves to be more efficient than the original P(hCMV*-1) in a cell-dependent manner. Furthermore, the SG-TRE preserves its enhanced regulation efficiency and its reduced basal leakiness in the context of a single positive feedback regulatory vector that presents ease of delivery of the system for use in vivo. Finally, in vivo, the biological function of granulocyte-macrophage colony stimulating factor is tightly regulated in the context of SG-TRE delivered via adeno-associated viruses.

Animals↗
PubMed1993

Analysis of the human MBP promoter in primary cultures of oligodendrocytes: positive and negative cis-acting elements in the proximal MBP promoter mediate oligodendrocyte-specific expression of MBP.

Since the regulation of myelin basic protein expression depends primarily on the initiation of transcription, we analyzed the 5' flanking region of the human myelin basic protein gene in transient transfection studies in primary cultures of developing oligodendrocytes. We demonstrated that 149 base pairs 5' of the initiation of transcription was sufficient to direct oligodendrocyte-specific expression of myelin basic protein. The capsite of the fusion transcript was identical with that of the endogenous myelin basic protein transcript, and chloramphenicol acetyl transferase reporter gene expression was restricted to oligodendrocytes in these cultures. Within this 149 base pair region, one distal, negative cis-acting segment, containing a consensus nuclear factor I site, and one proximal, positive cis-acting segment were identified. The distal segment behaved more negatively in Cos-7 cells than in oligodendrocytes, reducing expression to background levels. Furthermore, these functionally important cis-acting segments bound oligodendrocyte nuclear proteins in a pattern differing from other cells, including Cos-7 cells. Interestingly, the distal segment increased heterologous SV40 promoter activity in oligodendrocytes but had no effect on the SV40 promoter in Cos-7 cells. We conclude that the functionally negative distal segment may mediate oligodendrocyte-specific expression of MBP by restricting its expression in other cells. These experiments strongly support using primary cultures of oligodendrocytes for analyzing the myelin-specific promoters.

Animals↗
PubMed2004

An efficiently regulated promoter system for Cryptococcus neoformans utilizing the CTR4 promoter.

Cryptococcus neoformans is an opportunistic fungal pathogen responsible for serious meningitis. Although many useful molecular tools have been developed for its study, there are currently few inducible promoters available for general use. To address this need, we have constructed expression plasmids incorporating upstream elements of the C. neoformans copper transporter gene CTR4, and tested them in C. neoformans serotypes A and D. In response to copper deprivation, these plasmids mediate high-level expression of a reporter protein. This expression can be completely repressed using physiologically low concentrations of copper. Notably, this new family of copper-sensing promoters demonstrates excellent expression in serotype A, contrasting with other available promoters. These plasmids therefore offer efficient and regulated expression for both serotypes A and D, and should be valuable tools for the C. neoformans research community.

Cation Transport Proteins↗
PubMed1994

Hepatocyte nuclear factor-3 (HNF-3) binds to the insulin response sequence in the IGF binding protein-1 (IGFBP-1) promoter and enhances promoter function.

IGF binding protein-1 is an important short-term modulator of IGF bioavailability. Hepatic transcription of IGFBP-1 is increased by glucocorticoids and suppressed by insulin. We previously identified adjacent glucocorticoid and insulin response sequences approximately 90 bp 5' to the RNA cap site in the IGFBP-1 promoter. This insulin response sequence contains a sequence highly related (10/12 bases) to a consensus HNF-3 binding sequence. Gel shift and supershift studies confirm that this sequence binds HNF-3 alpha, beta and gamma. Co-expression of HNF-3 beta enhances IGFBP-1 promoter activity in NIH-3T3 cells. Mutation of this HNF-3 binding sequence disrupts this effect as well as the ability of glucocorticoids to stimulate and of insulin to inhibit IGFBP-1 promoter activity in H4IIE and HepG2 hepatoma cells. HNF-3 binding at this site may play an important role in the multihormonal regulation of hepatic IGFBP-1 gene expression.

3T3 Cells↗
PubMed2002

Promoter analysis of tumor suppressor gene PTEN: identification of minimum promoter region.

Mutations of PTEN, a tumor suppressor gene located on chromosome 10, which encodes a protein-tyrosine and lipid-phosphatase, are prevalent in various human cancers, including glioblastoma. Despite extensive characterization of PTEN mutations in human cancers and a relatively good understanding of the molecular roles of PTEN in the control of cellular processes, little is known about modes of PTEN regulation. To understand the regulation of expression of the tumor suppressor gene PTEN, we isolated a 2212 bp fragment from the human BAC clone 46B12 DNA. The 3' end of this fragment starts at the Not I site of -745 relative to the first translation codon ATG (+1) and ends at the Sal I site of -2957 at the 5' end. Using classical 5'RACE and primer extension techniques, nine start sites were observed between -817 and -984 upstream of the ATG start site. We located a 137 bp fragment (-958/-821) as the minimum promoter region using promoter deletion and luciferase assays. A 704 bp fragment (-33/-737) downstream of the 2212 bp fragment was also cloned. As indicated by luciferase assays, the data show that this region possesses no promoter function. Interestingly, a p53 binding sequence is located within the 599 bp fragment (-1344/-745), although p53 expression had a minimal effect on PTEN, demonstrating its insignificant role in PTEN gene expression.

5' Flanking Region↗
PubMed1992

MNF1, a leaf tissue-specific DNA-binding protein of maize, interacts with the cauliflower mosaic virus 35S promoter as well as the C4 photosynthetic phosphoenolpyruvate carboxylase gene promoter.

When gel shift assays were performed with maize nuclear extract and a DNA fragment containing the cauliflower mosaic virus (CaMV) 35S promoter, three DNA-protein complexes were observed. Analyses with nuclear extracts prepared from green leaves, etiolated leaves, stems and roots showed that the complexes resulted from the existence of at least two nuclear factors. One of them is presumably a constitutive nuclear factor found in all tissues tested, and another is a leaf-specific factor present both in green and etiolated leaves. This leaf-specific nuclear factor seemed to be identical to MNF1, previously identified as a factor interacting with the promoter of the maize gene for phosphoenolpyruvate carboxylase involved in the C4 photosynthesis. Deletion analysis revealed that MNF1 binds to the sequence from -281 to -235 relative to the transcription start site of the CaMV 35S promoter. MNF1-like nuclear protein was also found in tobacco nuclear extracts. The possibility that MNF1 participates as a positive trans-acting factor in the expression of genes in maize leaves is discussed.

Base Sequence↗
PubMed1996

Functional dissection of a napin gene promoter: identification of promoter elements required for embryo and endosperm-specific transcription.

The promoter region (-309 to +44) of the Brassica napus storage protein gene napA was studied in transgenic tobacco by successive 5' as well as internal deletions fused to the reporter gene GUS (beta-glucuronidase). The expression in the two main tissues of the seed, the endosperm and the embryo, was shown to be differentially regulated. This tissue-specific regulation within the seed was found to affect the developmental expression during seed development. The region between -309 to -152, which has a large effect on quantitative expression, was shown to harbour four elements regulating embryo and one regulating endosperm expression. This region also displayed enhancer activity. Deletion of eight bp from position -152 to position -144 totally abolished the activity of the napA promoter. This deletion disrupted a cis element with similarity to an ABA-responsive element (ABRE) overlapping with an E-box, demonstrating its crucial importance for quantitative expression. An internal deletion of the region -133 to -120, resulted in increased activity in both leaves and endosperm and a decreased activity in the embryo. Within this region, a cis element similar to the (CA)n element, found in other storage protein promoters, was identified. This suggest that the (CA)n element is important for conferring seed specificity by serving both as an activator and a repressor element.

2S Albumins, Plant↗
PubMed1990

An in vitro transcription termination system to analyze chloroplast promoters: identification of multiple promoters for the spinach atpB gene.

Promoters for spinach chloroplast genes were cloned 5' to a strong factor-independent transcription terminator from E. coli. These "minigene" constructions were transcribed in vitro by a transcriptionally active extract of spinach chloroplasts. Transcription of supercoiled DNA templates resulted in synthesis of discretely-sized RNAs that were readily quantifiable. The efficiency of transcription was up to 3.5 RNAs per template. The transcription termination system described in this report was used to identify the primary transcripts for the plastid atpB gene. Four in vivo transcripts for the atpB gene have been previously identified with 5' untranslated leaders of approximately 455, 275, 180 and 100 nucleotides, respectively. In this report we show that the "-455", "-275" and "-180" regions function as chloroplast promoters in vitro. In addition, a fourth promoter was found that yields a primary transcript totally lacking an untranslated leader.

Adenosine Triphosphatases↗
PubMed1995

Psychology, health promotion and aesthemiology. Paper one: Social cognition models as a framework for health promotion: necessary, but not sufficient.

Much of health promotion is premised on the notion that health-related behaviours are under individual control, and strongly influenced by intra-psychic factors, including knowledge and attitudes. The emphasis placed on such factors has led to a neglect of the social and material context in which the individual is situated. This paper describes a number of psychological theories which have influenced health promotion, and suggests ways in which a wider set of psychological theories and methods, which take into account social and material factors, may more usefully inform health promotion initiatives.

Cognition↗
PubMed1989

Transgenic regulation of moth chorion gene promoters in Drosophila: tissue, temporal, and quantitative control of four bidirectional promoters.

Bidirectional chorion gene promoter regions from three silkmoth species, Bombyx mori, Antheraea pernyi, or Antheraea polyphemus (members of two different moth families), were tested for their ability to transcriptionally activate a bacterial marker gene (chloramphenicol acetyltransferase) in transformant Drosophila. Relatively short 5' flanking DNA fragments (272-367 bp) of chorion gene pairs are sufficient to confer a high degree of tissue and choriogenic stage specificity of expression to the marker gene. Thus, significant conservation of molecular interactions controlling transcription during choriogenesis is observed between the distantly related orders, Lepidoptera and Diptera. However, quantitative and fine temporal regulation in the Drosophila host does not fully parallel the in situ regulation in moths, indicating that some regulatory protein-DNA interactions have diversified in the approximately 250 million years since the last common ancestor of these insect groups. Limited in vitro mutagenesis of a B. mori promoter DNA has shown that a central 189-bp region includes elements sufficient for the qualitative specificity of chorion-specific expression. The same experiments have shown that a previously identified essential element, centered on the TCACGT hexamer, is not sufficient for chorion-specific expression: an additional essential element or elements are found farther upstream, within a 112-bp DNA region. Comparisons of silkmoth and Drosophila chorion gene promoter sequences have identified some candidates for cis-acting elements involved in the developmental regulation of chorion gene expression.

Animals↗
PubMed1988

The hyg gene promoter from Streptomyces hygroscopicus: a novel form of Streptomyces promoters.

A 207 bp DNA fragment from the 5' region of the hyg gene of Streptomyces hygroscopicus was located preceding a DNA sequence encoding the mature form of human interferon alpha 2. This gene fusion, inserted in the Streptomyces vector pIJ702, expressed interferon activity in Streptomyces lividans indicating that the 207 bp sequence has promoter activity. The transcription initiation site was located. No significant homology with previously described Streptomyces promoters could be found. It appears therefore, it represents a novel class of Streptomyces promoters.

Base Sequence↗
PubMed1993

An improved retroviral vector for assaying promoter activity. Analysis of promoter interference in pIP211 vector.

We recently developed a novel promoter assay system using a retroviral vector (pIP200 series). Transcription from the internal promoter, which had been inserted for the promoter assay, was shown to be interfered with by transcription from the upstream long terminal repeat (LTR). Here we report a new high-titer 'self-inactivating' vector, in which transcription interference was virtually eliminated. This new vector was constructed by introducing only a very minor mutation into the 'TATA box' in the 3'-LTR. This mutation was successfully transferred to the 5'-LTR after reverse transcription, yielding a provirus incapable of transcribing viral RNA. The viral titer was not reduced by the mutation, permitting general application of this virus.

3T3 Cells↗
PubMed1987

SV40 late promoter: contribution of the initiation site sequences to basal late promoter activity.

We have previously shown that the +7 to -53 element of the SV40 late promoter (nt 273 to nt 332) does not have any promoter activity, but is able to stimulate the late promoter activity of the enhancer element. The +7 to -53 element contains several late transcriptional initiation sites and we have shown that its removal results in an increase in the heterogeneity of initiation sites. Furthermore we found that inversion of the +7 to -53 element does not adversely affect the efficiency of late transcription. However, when the +7 to -53 element was inverted, transcription initiated from a single site at nt 302. In fact, we noticed that there is a consensus TATA box signal 26 nt upstream of this single site in the inverted +7 to -53 element. These results may indicate that the ability of +7 to -53 element to function in both orientations is due to the fact that, in both orientations, it possesses sequences capable of fixing the initiation sites of transcription.

Genes, Viral↗
PubMed1992

Characterization of transcription and processing from plasmids that use polIII and a yeast tRNA gene as promoter to transcribe promoter-deficient downstream DNA.

Transfer RNA (tRNA) with mutations affecting the internal promoters and thereby causing them to be nontranscribable by polIII (exemplified, e.g., by nematode tDNAPro with large insertions between the two internal promoters) could be transcribed by polIII both in vitro (yeast) and in vivo (oocytes) when cloned behind a yeast tRNAArg gene. PolIII initiated RNA synthesis could also proceed into a downstream structural gene normally read by polIII. the resultant yeast-nematode dimeric tRNA linked in front of mRNA sequences was recognized by processing enzymes to give mature tRNA. Thus, a yeast tRNA gene preceded by its 5' flank can function as a promoter for polIII transcription of any DNA, also of DNA coding for genes that otherwise could not have been expressed either in vitro or in vivo.

Animals↗