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P Angel

Publications and source records attributed to P Angel.

87 records · Page 5Linked to original sources
PubMed1989

Jun and v-jun contain multiple regions that participate in transcriptional activation in an interdependent manner.

Transcription factor AP1 is a heteromeric complex composed of the Jun and Fos proteins. It has been shown that by associating with Jun, Fos increases Jun's ability to bind DNA and activate transcription. To determine the roles of the two proteins, we undertook the functional analysis described here. We show that both the cellular Jun and its viral counterpart, v-Jun, are efficient transcriptional activators even in the absence of Fos. The Jun proteins contain at least three separate regions responsible for transcriptional activation in F9 cells, which act in an additive manner. All of these regions contain several acidic amino acid residues that appear to be functionally important and interact with a titratable target. Although trans-activation by Fos was previously shown to be dependent on the presence of Jun, by fusing Fos to a heterologous DNA-binding domain we show that once given the ability to bind DNA on its own, Fos is also an independent trans-activator. Both Jun and Fos contribute to trans-activation by the AP1 complex, and the augmentation of Jun activity by Fos is probably due to the increased DNA-binding activity of the Jun:Fos heterodimer.

Amino Acid Sequence↗
PubMed1988

The jun proto-oncogene is positively autoregulated by its product, Jun/AP-1.

Binding of the human transcription factor Jun/AP-1 to a conserved 8 bp nucleotide sequence (TRE) is responsible for increased transcription of different cellular genes in response to tumor promoters, such as TPA, and serum factors. Enhanced Jun/AP-1 activity in TPA-stimulated cells is regulated by two different mechanisms: a posttranslational event acting on pre-existing Jun/AP-1 molecules, and transcriptional activation of jun gene expression leading to an increase in the total amount of Jun/AP-1. Induction of jun transcription in response to TPA is mediated by binding of Jun/AP-1 to a high-affinity AP-1 binding site in the jun promoter region. Site-specific mutagenesis of this binding site prevents TPA induction and trans-activation by Jun/AP-1. These results clearly demonstrate that jun transcription is directly stimulated by its own gene product. This positive regulatory loop is likely to be responsible for prolonging the transient signals generated by activation of protein kinase C.

Cells, Cultured↗
PubMed1988

Oncogene jun encodes a sequence-specific trans-activator similar to AP-1.

Proto-oncogenes encode proteins with three main sites of action: the cell-surface membrane, the cytoplasm and the nucleus. Although the exact biochemical function of most proto-oncogene products is not understood, several of them are known to be involved in signal transduction. A role in gene regulation through DNA binding has been suggested for a recently isolated member of the group of oncogenes acting at the nucleus, v-jun. The C-terminus of the putative v-jun-encoded protein is similar in sequence to the C-terminus of the yeast transcriptional activator GCN4 (refs 8, 9), which forms its minimal DNA-binding domain. GCN4 binds to specific sites whose consensus sequence is highly similar to the recognition sequence of the mammalian transcriptional activator AP-1 (refs 12, 13). Like GCN4, AP-1 binds to promoter elements of specific genes and activates their transcription. Because of the similarity between the recognition sites for GCN4 and AP-1, we examined the possibility that AP-1 could be the product of the c-jun proto-oncogene. The experimental results reported here indicate that the JUN oncoprotein is a sequence-specific transcriptional activator similar to AP-1.

Base Sequence↗
PubMed1988

Structure and chromosomal localization of the functional intronless human JUN protooncogene.

The JUN protooncogene encodes a protein that is functionally and biochemically identical to the transcription factor AP-1 (activator protein 1). To understand the structure and regulation of this important gene, a genomic clone of human JUN was isolated and its primary structure and transcription pattern were determined. Most surprisingly, the sequence of the genomic clone was found to be contiguous with the sequence of the JUN cDNA, suggesting that it lacks introns. RNase protection experiments confirm that JUN is an intronless gene that yields several transcripts due to 5' and 3' heterogeneities. Transfection experiments show that the cloned gene is functional, as it encodes a trans-acting factor that stimulates transcription of AP-1-dependent reporter gene. In situ hybridization was used to map JUN to chromosomal region 1p31-32. Interestingly, this region is frequently deleted in neuroblastomas, suggesting that elimination of AP-1 may play an important role in the pathogenesis of this disease.

Amino Acid Sequence↗
PubMed1987

Phorbol ester-inducible genes contain a common cis element recognized by a TPA-modulated trans-acting factor.

The promoter regions of several phorbol diester-(TPA-) inducible genes (collagenase, stromelysin, hMT IIA, and SV40) share a conserved 9 bp motif. Synthetic copies of these closely related sequences conferred TPA inducibility upon heterologous promoters. Footprinting analysis indicated that these TPA-responsive elements (TREs) are recognized by a common cellular protein: the previously described transcription factor AP-1. A point mutation that eliminated the basal and induced activity of the TRE also interfered with its ability to bind AP-1. Treatment of cultured cells with TPA led to a rapid 3- to 4-fold increase in TRE binding activity, by a posttranslational mechanism. These results strongly suggest that AP-1 is at the receiving end of a complex pathway responsible for transmitting the effects of phorbol ester tumor promoters from the plasma membrane to the transcriptional machinery.

Animals↗
PubMed1987

Stimulation of procollagenase synthesis parallels increases in cellular procollagenase mRNA in human articular chondrocytes exposed to recombinant interleukin 1 beta or phorbol ester.

Interleukin 1, a product predominantly of monocytes, increases the synthesis and release of procollagenase and prostaglandin E2 by mesenchymal target cells such as synovial fibroblasts and articular chondrocytes, an effect mimicked by some phorbol esters. In order to determine the mechanisms underlying these responses primary cultures of human articular chondrocytes were preincubated with recombinant human interleukin 1 beta or the phorbol ester, phorbol 12-myristate 13-acetate, in the presence or absence of the cyclooxygenase inhibitor, indomethacin. Interleukin 1 beta or phorbol ester increased the levels of procollagenase (assayed after trypsin activation) and the labeling of several medium proteins by cells incubated with [35S]methionine, independent of prostaglandin synthesis. The labeling of a 55 kD protein immunocomplexed with antibodies to procollagenase was also increased. The increased synthesis of procollagenase was paralleled by increased cellular levels of procollagenase mRNA, determined with a cDNA probe coding for human procollagenase. Thus the increased synthesis of procollagenase in response to the inflammatory mediator, interleukin 1, is controlled at a pretranslational level, possibly at the level of transcription.

Cartilage, Articular↗
PubMed1987

Posttranscriptional regulation of c-fos mRNA expression.

The transient induction of c-fos mRNA and protein suggests that regulation occurs not only by transcriptional activation but also at the level of turnover of the gene product. Here we present evidence for the rapid turnover of c-fos mRNA and some of the requirements for its specific degradation. The half life of induced mature cytoplasmic c-fos mRNA is 9 min in both serum-starved and growing primary human fibroblasts and in NIH 3T3 cells. A structure present at the 3' end of the c-fos mRNA molecule is involved in its low stability since the substitution or the removal of the untranslated 3' portion prolongues the RNA life time. The rapid turnover of fos mRNA requires, in addition, continued protein synthesis. Treatment of cells with cycloheximide stabilizes c-fos mRNA. Washing out cycloheximide reestablishes the rapid turnover. Both changes occur with lag periods of less than 17 minutes.

Adult↗
PubMed1987

Transforming growth factor beta modulates the expression of collagenase and metalloproteinase inhibitor.

Exposure of quiescent MRC-5 human fibroblasts to growth factors such as epidermal growth factor, basic fibroblast growth factor or embryonal carcinoma-derived growth factor resulted in the induction of mRNA transcripts encoding the metalloproteinases collagenase and stromelysin and the specific metalloproteinase inhibitor TIMP, whilst expression of collagen and fibronectin was relatively unaffected. Exposure of quiescent cells to growth factors in the presence of transforming growth factor beta (TGF-beta) resulted in inhibition of collagenase induction and a synergistic increase in TIMP expression. TGF-beta alone did not significantly induce metalloproteinase or TIMP expression. These effects on mRNA transcripts were reflected in increased secretion of TIMP protein and collagenase activity. Nuclear run-off analysis of growth factor-induced transcription revealed that the TGF-beta modulation of TIMP and collagenase expression was due to transcriptional mechanisms. The observations suggest that TGF-beta exerts a selective effect on extracellular matrix deposition by modulating the action of other growth factors on metalloproteinase and TIMP expression.

Cell Line↗
PubMed1987

12-O-tetradecanoyl-phorbol-13-acetate induction of the human collagenase gene is mediated by an inducible enhancer element located in the 5'-flanking region.

Genomic clones coding for human fibroblast collagenase were isolated. By constructing and transfecting mutants with 5' and 3' deletion mutations of the 5' control region of the gene into human or murine cells, we delimited a 32-base-pair sequence at positions -73 to -42 which is required for the induction of transcription by the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate. The DNA element behaves as a 12-O-tetradecanoyl-phorbol-13-acetate-inducible enhancer: it mediates the stimulation of transcription to the heterologous herpes simplex virus thymidine kinase promoter and acts in a position- and orientation-independent manner. Differences in enhancer efficiency in different cell lines are interpreted to indicate differences in the activity of a trans-acting factor.

Adult↗
PubMed1986

Comparison of human stromelysin and collagenase by cloning and sequence analysis.

A comparison of the cDNA-derived amino acid sequences of human stromelysin and collagenase with the N-terminal sequences of purified enzymes reveals that these metalloproteinases are highly conserved and that they are secreted as proenzymes. A putative zinc-binding site was identified by its homology with the zinc-chelating sequence of thermolysin. These sequences permitted the identification of: transin, a protein induced in rat fibroblasts either exposed to growth factors or transformed by oncogenic viruses, as the rat homologue of stromelysin, and XHF1, a protein induced in human fibroblasts after treatment with tumourigenic agents, as collagenase.

Amino Acid Sequence↗
PubMed1986

The mammalian genetic stress response.

A number of carcinogenic and cocarcinogenic agents induce new gene products in mammalian cells including primary human skin fibroblasts. These have been defined by cDNA cloning techniques, by protein resolutions in 2D PAGE and by the detection of new enzymatic functions. The uniform and transient genetic reaction is tentatively called the genetic stress response.

Animals↗
PubMed1986

Induction of metallothionein and other mRNA species by carcinogens and tumor promoters in primary human skin fibroblasts.

We used nucleic acid hybridization and cDNA cloning techniques to isolate human sequences that respond to the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). These clones were used as probes to examine changes of gene expression that occurred after the proliferation of exponentially growing primary human fibroblasts was arrested. Transcript levels detected by these probes were increased coordinately by treatment of the cells with UV light, mitomycin C, TPA, or the UV light-induced extracellular protein synthesis-inducing factor EPIF (M. Schorpp, U. Mallick, H. J. Rahmsdorf, and P. Herrlich, Cell 37:861-868, 1984). Proteins coded for by these transcripts were characterized by hybrid-promoted translation and by cDNA sequencing. One of the cDNA clones was homologous to the metallothionein IIa gene, and one set of related clones selected RNA for the secreted TPA-inducible protein XHF1 (U. Mallick, H. J. Rahmsdorf, N. Yamamoto, H. Ponta, R.-D. Wegner, and P. Herrlich, Proc. Natl. Acad. Sci. USA 79:7886-7890, 1982).

Cell Transformation, Neoplastic↗
PubMed1985

12-O-Tetradecanoylphorbol-13-acetate (TPA)-induced gene sequences in human primary diploid fibroblasts and their expression in SV40-transformed fibroblasts.

We have isolated cDNA sequences from TPA-treated primary human fibroblasts, which indicate RNA species that are coordinately regulated after treatment of these cells with either ultraviolet light, mitomycin C, the UV-induced factor EPIF, or TPA. The levels of RNA are elevated in Bloom syndrome (cells of two out of three patients). After transformation with SV40 one of the sequences is overexpressed while another one is reduced. Both genes maintain their inducibility by the agents mentioned.

Bloom Syndrome↗