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Query: UNIPROT:P05412 (c-Jun)
 11,453 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tumor promoters may bring about events that lead to neoplastic transformation by inducing specific promotion-relevant effector genes. Functional activation of the transacting transcription factor AP-1 by the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) may play an essential role in this process. Clonal genetic variants of mouse epidermal JB6 cells that are genetically susceptible (P+) or resistant (P-) to promotion of transformation by TPA were transfected with 3XTRE-CAT, a construct that has AP-1 cis-enhancer sequences attached to a reporter gene encoding chloramphenicol acetyltransferase (CAT). Transfected JB6 P+, but not P- variants, showed TPA-inducible CAT synthesis. Epidermal growth factor, another transformation promoter in JB6 cells, also caused P+ specific induction of CAT gene expression. These results demonstrate an association between induced AP-1 function and sensitivity to promotion of neoplastic transformation.
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PMID:AP1/jun function is differentially induced in promotion-sensitive and resistant JB6 cells. 254 2

The adenovirus early region 3 (E3) promoter is an early viral promoter which is strongly induced by the adenovirus transactivator protein E1A. DNase I footprinting with HeLa cell extracts has identified four factor-binding domains which appear to be involved in basal and E1A-induced transcriptional regulation. These binding domains may bind TATA region-binding factors (site I), the CREB/ATF protein (site II), the AP-1 protein (site III), and nuclear factor I/CTF (site IV). Recently, it has been shown that the DNA-binding domain of transcription factor AP-1 has homology with the yeast transcription factor GCN4 and that the yeast transactivator protein GAL4 is able to stimulate transcription in HeLa cells from promoters containing GAL4-binding sites. These results suggest an evolutionary conservation of both transcription factors and the mechanisms responsible for transcriptional activation in Saccharomyces cerevisiae and higher eucaryotic organisms. To determine whether similar patterns of transcriptional regulation were seen with the E3 promoter in HeLa and yeast cells, the E3 promoter fused to the chloramphenicol acetyltransferase (cat) gene was cloned into a high-copy-number plasmid and stably introduced into yeast cells. S1 analysis revealed that similar E3 promoter mRNA start sites were found in yeast and HeLa cells. DNase I footprinting with partially purified yeast extracts revealed that four regions of the E3 promoter were protected. Several of these regions were similar to binding sites determined by using HeLa cell extracts. Oligonucleotide mutagenesis of these binding domains indicated their importance in the transcriptional regulation of the E3 promoter in yeast cells. These results suggest that similar cellular transcription factor-binding sites may be involved in the regulation of promoters in both yeast and mammalian cells.
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PMID:Adenovirus transcriptional regulatory regions are conserved in mammalian cells and Saccharomyces cerevisiae. 297 53

In differentiated 3T3-F442A adipocytes, insulin stimulated rapid and transient phosphorylation of c-Jun. Insulin also stimulated phosphorylation of c-Fos and several Fos-related proteins (pp72, pp45, and pp39) as indicated by precipitation with anti-c-Fos antibody following exposure to denaturating conditions. Phosphorylation of c-Fos was stimulated by 7-fold by 60 min, while phosphorylation of Fos-related proteins reached maxima of 3.5-5.5-fold at 15 to 60 min. The increase in phosphorylated c-Fos was due to an increase in both c-Fos protein and the stoichiometry of c-Fos phosphorylation, and was not observed in c-fos (-/-) cells. Additionally, insulin stimulated phosphorylation of a protein with molecular mass of approximately 82 kDa on tyrosine residues by 2.5-fold within 30 min; this protein appeared to be immunologically related to c-Fos. These increases in the phosphorylation of AP-1 transcription factors correlated with a > 5-fold stimulation of expression of a 12-O-tetradecanoylphorbol-13-acetate-responsive element-chloramphenicol acetyltransferase reporter gene transiently transfected into 3T3-F442A cells. These results indicate that insulin stimulates the phosphorylation of AP-1 transcription factors and several Fos-related proteins on serine and tyrosine residues. This is associated with changes in AP-1-mediated gene expression in vivo, suggesting that AP-1 phosphorylation by insulin plays a role in insulin-regulated gene expression.
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PMID:Insulin stimulates phosphorylation of c-Jun, c-Fos, and Fos-related proteins in cultured adipocytes. 751 56

Anti-c-Src and anti-phosphotyrosine immunoprecipitates from receptor-like protein tyrosine phosphatase alpha (PTP alpha)-transfected and control rat embryo fibroblasts contain a 39-kDa phosphoprotein (p39) whose phosphorylation is enhanced by PTP alpha expression. The p39 that co-immunoprecipitates with c-Src has been identified as c-Jun by immunological and functional criteria; it is recognized by several different anti-c-Jun antibodies and binds to a c-Jun recognition element-containing oligonucleotide. Whereas the association of c-Src and c-Jun is unexpected, it may be of significance in PTP alpha signaling since we have previously demonstrated that c-Src is activated by PTP alpha (Zheng, X. M., Wang, Y., and Pallen, C. J. (1992) Nature 359, 336-339. Examination of c-Jun activity in these fibroblasts demonstrates that c-Jun DNA binding activity and c-Jun-mediated transcription of a chloramphenicol acetyltransferase reporter gene are elevated in PTP alpha-expressing cells. In addition to c-Jun activation, mitogen-activated protein kinase is activated in PTP alpha-expressing cells and translocated to the nuclei of these cells. The nuclear localization of activated mitogen-activated protein kinase and c-Jun suggests that their activation represents downstream events in the receptor-like PTP alpha-initiated signaling pathway(s).
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PMID:Expression of receptor-like protein tyrosine phosphatase alpha in rat embryo fibroblasts activates mitogen-activated protein kinase and c-Jun. 752 77

Loricrin gene expression is limited to terminally differentiating keratinocytes of stratified squamous epithelia. To define the regulatory elements that mediate the expression of the loricrin gene, we replaced the loricrin coding sequences from a 6.5-kilobase genomic fragment with the chloramphenicol acetyltransferase gene and transfected this construct into cultured mouse keratinocytes. High expression levels were observed in both undifferentiated as well as differentiating cells. Transgenic mice bearing a similar construct, but with beta-galactosidase as the reporter gene, corroborated these in vitro findings and showed tissue- and cell type-specific, but not differentiation-specific expression. Deletion analysis of the promoter region determined that sequences up to -60 base pairs from the start of transcription could be removed without significant loss of promoter activity. Within these proximal 60 base pairs is an evolutionarily conserved AP-1 element that is recognized by both purified c-Jun and AP-1 factors from keratinocytes in vitro. Mutation of this AP-1 site abolished the activity of the loricrin promoter. These studies show that elements directing expression of the loricrin gene to the stratified squamous epithelia are contained within a 6.5-kilobase genomic fragment, and those elements required to restrict expression to differentiated keratinocytes lie outside this region.
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PMID:The proximal promoter of the mouse loricrin gene contains a functional AP-1 element and directs keratinocyte-specific but not differentiation-specific expression. 773 16

Marek's disease virus (MDV) is an avian herpesvirus that induces a variety of diseases, including T-cell lymphomas, in chickens. In latently infected, transformed lymphoid cells, very few viral transcripts or proteins are detected. We previously described a gene, meq (MDV EcoQ), which is persistently expressed in MDV-transformed tumor samples and cell lines. meq codes for a 339-amino-acid protein with a basic-leucine zipper domain near its N terminus and a proline-rich domain near its C terminus. The basic-leucine zipper domain shows homology with Jun/Fos family proteins, whereas the proline-rich domain resembles that of the WT-1 tumor suppressor protein. These structural features raise the possibility that Meq functions as a transcription factor in regulating viral latency or oncogenesis. In this report, we show that the proline-rich domain is a potent transcription activator when fused to the yeast (Saccharomyces cerevisiae) Gal4(1-147) DNA-binding domain. The transactivation activity maps to the C-terminal 130 amino acids, with the last 33 amino acids essential. In the absence of these 33 amino acids, a two-and-one-half proline-rich repeat structure was found to exhibit repression activity. We further show that Meq is able to dimerize not only with itself but also with c-Jun. Meq/c-Jun heterodimers bind to an AP1-like sequence in the meq promoter region with an affinity much greater than that of Meq/Meq or c-Jun/c-Jun homodimers. Cotransfection chloramphenicol acetyltransferase assays suggest that the Meq/c-Jun heterodimers can up-regulate Meq expression in both chicken embryo fibroblasts and F9 cells. Our data provide the first biochemical evidence that Meq is a transcriptional factor and identify c-Jun as one of Meq's interacting partners.
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PMID:Transactivation activity of Meq, a Marek's disease herpesvirus bZIP protein persistently expressed in latently infected transformed T cells. 776 61

The functional induction of c-fos in the sodium butyrate-induced differentiation of F-98 glioma cells was studied. Fos protein level was increased by butyrate. In contrast, c-Jun protein was constitutively expressed and was not affected by butyrate. Gel-retardation assay indicates Fos as a component of the complex formed between the consensus oligonucleotide of the TPA (PMA, phorbol 12-myristate 13-acetate) response element (TRE) and nuclear extract prepared from butyrate-treated cells. Transfection studies showed that butyrate increased transcription from a multimeric TRE-driven reporter construct, and the effect was mimicked by transfecting cells with fos-expression plasmid. Furthermore, under conditions of c-fos over-expression, transactivation by butyrate was essentially abolished. These data suggest that Fos induction had a functional role in gene activation. Characterization of stable c-fos transfectants demonstrated that these cells displayed alterations in morphology, showed serum-dependent growth, had slower growth rates and grew to lower saturation densities than did untransfected F-98 cells or transfected cells that did not express c-fos. Immunofluorescent staining indicated that fos transfectants also had elevated glial fibrillary acidic protein ('GFAP') expression. Transfection of the c-fos promoter-chloramphenicol acetyltransferase fusion gene into F-98 cells revealed that activation of c-fos by butyrate was exerted at the promoter level, and sequences located within nucleotides -757 to -402 of the c-fos promoter were responsible for butyrate induction. Our data indicate that transcriptional activation of c-fos through its promoter by butyrate resulted in increased Fos protein expression. Transfection studies show that both c-fos and butyrate activate TRE-containing genes, and fos may be a downstream mediator of butyrate. Furthermore, expression of c-fos plays a major role in modulating the growth properties of F-98 cells.
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PMID:Analysis of c-fos expression in the butyrate-induced F-98 glioma cell differentiation. 786 28

The induction of the AP-1 transcription factor has been ascribed to the early events leading to T lymphocyte activation. We have examined the possibility that stimulation of phospholipase D (PLD) may regulate activation of transcription factor AP-1 in human T cells by transfecting human T lymphocyte Jurkat cells with a plasmid containing an AP-1 enhancer element and a chloramphenicol acetyltransferase reporter gene. We have detected activatable PLD in Jurkat cells, and we have found that addition of phosphatidic acid (PA), the physiologic product of PLD action on phospholipids, is rapidly incorporated into Jurkat cells and leads to activation of transcription factor AP-1. Treatment of Jurkat cells with anti-CD3 mAb activated both PLD and transcription factor AP-1. Wortmannin, an inhibitor of receptor-coupled PLD activation, blocked the anti-CD3-induced increases in both PLD activity and AP-1 enhancer activity. We found a good correlation in the transfected cells between PLD activation and induction of AP-1 enhancer activity under different experimental conditions. Furthermore, ethanol, an inhibitor of the PLD pathway, blocked the anti-CD3-stimulated AP-1 enhancer activity. However, this anti-CD3-mediated response was not inhibited by neomycin, an inhibitor of phosphoinositide hydrolysis. The increases in AP-1 enhancer activity induced by PA or anti-CD3 mAb were efficiently abrogated by the presence of propranolol, an inhibitor of PA phosphohydrolase and protein kinase C (PKC). Furthermore, the PA- and the anti-CD3-induced increases in AP-1 enhancer activity were blocked by the presence of PKC inhibitors or by PKC down-regulation. These data indicate that PLD stimulation can activate the transcription factor AP-1 in T lymphocytes, and suggest that the induction of AP-1 enhancer factor activity by PA is mediated via PKC stimulation, either through a direct activating effect of PA or through PA-derived diacylglycerol formation. These data also provide evidence for a role of PLD-derived lipids in the induction of AP-1 enhancer activity resulting from stimulation of the TCR/CD3 complex, suggesting that increased PLD activity can play an important role in T lymphocyte activation.
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PMID:Involvement of phospholipase D in the activation of transcription factor AP-1 in human T lymphoid Jurkat cells. 807 60

Sequences of 31 bp containing putative AP-1 and AP-4 binding sequences in the U3 region of the feline immunodeficiency virus (FIV) long terminal repeat (LTR) were deleted and the basal promoter activity of the LTR was measured by the chloramphenicol acetyltransferase (CAT) assay. The activity of the FIV LTR was reduced in Felis catus whole foetus 4 (fcwf-4) cells and Crandell feline kidney cells by this deletion. Cotransfection of murine c-Fos or c-Jun expression plasmids with the FIV LTR-CAT reporter plasmid into fcwf-4 cells revealed that FIV LTR could be activated by c-Fos but not c-Jun in the cells. The mutated LTR was introduced into an infectious molecular clone of FIV and the replication rate and the cytopathogenic activity of the mutant were compared with those of the wild-type in two feline CD4-positive T lymphoblastoid cell lines. It was found that the rate and activity of the mutant were almost the same as those of the wild-type. From these data, we conclude that the 31 bp fragment is important for achieving maximal expression of the FIV genome, but not required for the replication of FIV in feline T lymphocytes.
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PMID:The AP-1 binding site in the feline immunodeficiency virus long terminal repeat is not required for virus replication in feline T lymphocytes. 839 13

We have characterized the 5'-flanking region of the alpha-subunit gene of the human pyruvate dehydrogenase (E1). DNase I footprinting with rat liver nuclear extracts identified 7 major protein-binding domains termed P1 through P7 in a 796 base pair DNA fragment (base pairs -763 to +33). P1 through P4 are clustered in the -221/+33 region. These protein-binding domains contain several known consensus sequences such as a TATA box, CAAT box, Sp1, and CRE, which all have previously been implicated in the constitutive transcription of several genes. Oligonucleotide competition studies indicate that oligonucleotides specific for CTF/NF-1 and Sp1 displaced the nuclear proteins bound to the CAAT box (within P3) and an Sp1 site (within P4), respectively. Several other well-characterized and purified transactivators (c-Fos, c-Jun, C/EBP, AP-2, and Sp1) have been shown to bind to the -221/+33 region. Other elements located upstream of the -221/+33 region, which includes nuclease protection domains P5-P7, are required for enhanced promoter activity of the 796 bp sequence. Promoter activity was measured by transient expression of a chloramphenicol acetyltransferase gene ligated to deletion fragments of the 5'-flanking region. Crucial element(s) for promoter activity and complex DNA-nuclear protein interactions were confined within a region spanning -221/+33. This region also retained more than 75% of the promoter activity of the 796 bp sequence. Additionally, this promoter region shows characteristics of both facultative and housekeeping gene promoters, suggesting complex transcriptional regulation.
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PMID:Multiple protein-binding domains and functional cis-elements in the 5'-flanking region of the human pyruvate dehydrogenase alpha-subunit gene. 847 54


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