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

The early genes E6 and E7 from human papillomaviruses (HPVs) play a key role in the development of cervical cancer. Modulation of E6 and E7 gene expression may alter tumour progression; therefore, modifiers of viral transcription such as hormones or growth factors are potential risk factors in cancer development. We have analysed the effects of epidermal growth factor (EGF) on E6/E7 mRNA from human papillomavirus type 16 (HPV-16) by Northern blot in two cell lines, SiHa cervical carcinoma cells, and HPK IA, an HPV-16-immortalized keratinocyte cell line. E6/E7 mRNA is EGF-inducible in SiHa cells, with the earliest response after 2 h. In contrast, in HPK IA cells no increase in E6/E7 RNA is observed, suggesting a differential EGF response of viral transcription in tumour cells compared with keratinocytes. We demonstrate that the cell type-specific HPV-16 enhancer is a target of EGF-induced signals, as its activity is amplified by EGF in SiHa cell transfections. However, when transfected into HPK IA keratinocytes, the viral enhancer shows no EGF response. The enhancer contains two binding sites for the transcription factor AP-1, a potential mediator of the EGF signalling cascade. Enhancer subfragments with single AP-1 binding sites are also EGF-responsive in SiHa cells. Mutating either AP-1 site in the complete enhancer decreases the EGF response, whereas a double mutation causes a complete loss of EGF regulation, suggesting that the EGF induction of HPV-16 early transcription requires AP-1 activation. We conclude that alterations of EGF responsiveness that increase viral oncogene expression may contribute to cervical cancer progression.
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PMID:Epidermal growth factor induction of human papillomavirus type 16 E6/E7 MRNA in tumor cells involves two AP-1 binding sites in the viral enhancer. 763 75

Human papillomavirus (HPV) type 16 and 18 viral genomes are frequently detected in cervical and penile cancer biopsies. Although this strongly suggests a prominent role for HPV infection in the development of genital cancer, other genetic or environmental factors are also involved. Genital cancer is postulated to result from loss of cellular control functions, which leads to an unregulated expression of HPV oncogenic proteins. In our study, we determined the trans-activating properties of nuclear proto-oncogene proteins c-Fos, c-Jun and c-Myc on P97 enhancer/promoter activity of HPV16. Using a CAT-reporter construct containing the HPV16 enhancer/promoter element, we investigated the trans-activating effects of c-Fos, c-Jun, c-Myc, and E2 in cervical HT-3 cells. c-Fos and c-Jun overexpression resulted in a 3.3- and 3.1-fold up-regulation of CAT activity. Only 2-fold induction was determined by co-transfection with c-myc and the viral transcription factor E2. Based on these findings, we investigated the expression of HPV DNA (16 and 18) as well as nuclear proto-oncogenes (c-fos, c-jun and c-myc) in nine cervical cancers by in situ hybridisation. In six out of nine carcinomas, HPV16 and/or HPV18 DNA was detectable. All tumours showed an intense and homogeneous expression of c-fos and c-jun mRNA, while the signal for c-myc was detectable only in four specimens. These data suggest that deregulation of nuclear proto-oncogene expression may contribute to an overexpression of HPV-derived oncogenic proteins (E6 and E7), which is generally hypothesised to be an important step in the malignant transformation of HPV-associated tumours.
Br J Cancer 1995 May
PMID:Nuclear proto-oncogene products transactivate the human papillomavirus type 16 promoter. 773 93

Using deletion analysis and site-specific mutagenesis to map the 5' regulatory region of the DNA methyltransferase (MeTase) gene, we show that a 106-bp sequence (at -1744 to -1650) bearing three AP-1 sites is responsible for induction of DNA MeTase promoter activity. Using transient cotransfection chloramphenicol acetyl-transferase assays in P19 cells, we show that the DNA MeTase promoter is induced by c-Jun or Ha-Ras but not by a dominant negative mutant of Jun, delta 9. The activation of the DNA MeTase promoter by Jun is inhibited in a ligand dependent manner by the glucocorticoid receptor. Stable expression of Ha-Ras in P19 cells results in induction of transcription of the DNA MeTase mRNA as determined by nuclear run-on assays and the steady state levels of DNA MeTase mRNA as determined by an RNase protection assay. These experiments establish a potential molecular link between nodal cellular signaling pathways and the control of expression of the DNA MeTase gene. This provides us with a possible molecular explanation for the hyperactivation of DNA MeTase in many cancer cells and suggests that DNA MeTase is one possible downstream effector of Ras.
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PMID:Regulation of the DNA methyltransferase by the Ras-AP-1 signaling pathway. 782 90

Single ultraviolet (u.v.) irradiation of mammalian cells in culture evokes the transcriptional activation of various proto-oncogenes, among them members of the fos/jun family which are known to play an important role in cell proliferation and differentiation. u.v. exposure of mammalian skin results in growth arrest and cell death followed by hyperproliferation of epidermal cells. To obtain information in vivo about a possible relationship between u.v.-induced proto-oncogene expression and cellular alterations, we have analysed the expression of c-fos, fosB, c-jun, junB, bcl-2 and bax in rat epidermis after single and chronic u.v. irradiation. We present data demonstrating that the transcripts of these genes are constitutively expressed in the epidermis and that expression is differentially modulated by u.v. exposure. Single u.v. irradiation causes a rapid and sustained increase in c-jun, junB and c-fos mRNA and a decline in bcl-2 transcripts, whereas expression of bax remained unchanged. c-Fos and c-Jun immunoreactivity was localized throughout the epidermal cell layers 1.5 h after single irradiation, but restricted to basal cells at 48 h suggesting an involvement in both u.v.-induced apoptosis and hyperproliferation. 48 h after chronic exposure a significantly higher induction and a totally different pattern of epidermal proto-oncogene expression was detectable which may be associated with malignancy. Superfusion of rat skin with c-fos antisense oligodeoxynucleotides inhibited the increase in c-Fos immunolabeled epidermal cells 1.5 h after single u.v. irradiation demonstrating that antisense oligodeoxynucleotides are capable of penetrating mammalian skin and modulating the u.v. response in vivo. However, suppression of the early c-Fos activation did not significantly affect the formation of sunburn cells in the u.v.-exposed epidermis. Thus, c-Fos does not seem to play a major role in u.v.-induced apoptosis or other members of the fos/jun family may compensate for a loss in c-Fos.
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PMID:Differential regulation of c-fos, fosB, c-jun, junB, bcl-2 and bax expression in rat skin following single or chronic ultraviolet irradiation and in vivo modulation by antisense oligodeoxynucleotide superfusion. 793 45

Although the DNA topoisomerases are critical intracellular targets of a number of clinically important anticancer drugs, the mechanism(s) by which inhibition of these enzymes causes cell death are poorly understood. We found that treatment of human leukemic lymphoblasts (CCRF-CEM) with teniposide (VM-26), under conditions that stabilize DNA-topoisomerase II complexes, caused the formation of internucleosomal DNA ladders. However, it appeared unlikely that the VM-26-stabilized DNA-topoisomerase II-cleavable complexes directly produce these internucleosomal DNA ladders, since similar nucleosomal DNA ladders were observed following either continuous or a short (1 h) exposure of cells to VM-26. Under continuous exposure to VM-26, the internucleosomal DNA ladders were associated with the transient induction of c-jun mRNA in a dose-dependent fashion, reaching maximum expression at 6 h after treatment with VM-26 and being down-regulated to basal levels by 12 h. The induction of c-jun mRNA by VM-26 apparently preceded DNA ladder formation. However, in CEM sublines selected for resistance to VM-26 (CEM/VM-1 and CEM/VM-1-5; approximately 50- and 140-fold resistant, respectively) and which display the phenotype of multidrug resistance associated with altered DNA topoisomerase II (at-MDR), we found that the induction of c-jun mRNA by VM-26 and subsequent DNA ladder formation were progressively attenuated in proportion to the resistance of the cells, apparently due in part to decreased stabilization of DNA-topoisomerase II-cleavable complexes. Further, the attenuated induction of c-jun in the at-MDR cells was found to be associated with a decreased rate of c-jun transcription and an increase in the instability of its mRNA following VM-26 treatment. The attenuation of c-jun mRNA induction was also reflected in decreased production of c-Jun protein in the at-MDR cells. Of interest was the fact that no significant induction of c-fos mRNA by VM-26 was observed in either CEM or at-MDR cells. Furthermore, the induction of c-jun was related to the activation of AP-1 DNA-binding activity in a time- and dose-dependent manner in CEM cells, whereas the activation of AP-1 binding was attenuated in at-MDR cells in proportion to their resistance to VM-26. Using Jun and Fos family member antibody inhibition experiments in gel-mobility shift assays, we found that AP-1-binding activity appeared to be preferentially mediated by c-Jun/Fra-1 heterodimers in both CEM and at-MDR cells.(ABSTRACT TRUNCATED AT 400 WORDS)
Cancer Res 1994 Sep 15
PMID:Differences between drug-sensitive and -resistant human leukemic CEM cells in c-jun expression, AP-1 DNA-binding activity, and formation of Jun/Fos family dimers, and their association with internucleosomal DNA ladders after treatment with VM-26. 806 63

Jun and Fos are major components of the transcriptional complex AP-1 (Activator Protein-1), a collection of dimeric transcriptional activators composed of members of the Jun and Fos family of bZIP proteins, that bind to a common site known as TRE (TPA Responsive Element) or the AP-1 site. Transcription of c-jun is rapidly induced by exposure to different extra-cellular signals like growth factors, cytokines, tumor promoters (TPA), UV and other DNA-damaging agents. Transcriptional activation of c-jun is a two step mechanism. First, the pre-existing c-Jun protein is activated by posttranscriptional modifications, and second, modified c-Jun activates its own transcription, and the expression of AP-1-dependent genes. Modifications of c-Jun include dephosphorylations, phosphorylations and oxydo-reduction. The transcriptional activation by c-Jun is modulated by heterodimerization with other members of the bZIP family of proteins, and by transcriptional interference with other transcription factors like some members of the hormone nuclear receptors, or MyoD. AP-1 is tightly associated to both the control of cell proliferation and the oncogenic process. Constitutive activation of AP-1 leads to cell transformation in vitro, probably due to the accumulation of homodimeric c-Jun:c-Jun complexes. This hypothesis has been directly confirmed by constructing c-Jun hybrid proteins capable to form only homodimers. Deregulated expression of such proteins efficiently transforms primary cells in culture. These hybrid proteins constitute a powerful tool in order to identify new cellular functions AP-1-dependent, involved in the control of cell proliferation.
Bull Cancer 1993 Sep
PMID:[The C-Jun oncoprotein]. 820 56

The involvement of the nuclear protooncogenes c-fos and c-jun in the immediate early response of pig dermis cells was studied after in vivo gamma-irradiation. Following high radiation doses (8 to 48 Gy), the two protooncogenes were concomitantly induced, although c-fos induction was preferential. Both inductions were time and dose dependent. Therefore, the early response of the skin to high doses of radiation might involve heterodimeric activator protein 1 composed of c-Fos and c-Jun proteins. Following low radiation doses (0.5 to 2 Gy), c-jun was not induced. By contrast, dramatic c-fos induction was observed after 0.5 Gy, suggesting a specific role for c-fos at low doses.
Cancer Res 1993 Jul 15
PMID:Preferential induction of c-fos versus c-jun protooncogene during the immediate early response of pig skin to gamma-rays. 832 35

Nuclear levels of c-Jun, JunB, c-Fos, and LRF-1 (liver regeneration factor) are high for a large fraction of the G1 phase in regenerating liver and mitogen-stimulated hepatic cells. Previously, JunB was regarded as a less potent transcriptional activator than c-Jun that could also function as a repressor. However, we found that, like c-Jun, JunB alone or LRF-1/JunB strongly transactivates a cAMP-responsive promoter. Unlike c-Jun, JunB represses several AP-1 or activator of transcription factor site-containing promoters, and this inhibition is greatly enhanced in the presence of LRF-1. Here, we identify separate regions of JunB required for trans-activation and repression of these promoters. Deletion analysis shows that the region involved in trans-activation function is highly conserved among all Jun family members and corresponds to activator domain (A1) of c-Jun. In contrast, repression is maximal in the presence of both the DNA-binding domain and a region proximal to the basic region that is highly divergent among Jun proteins. Functional distinctions between Jun proteins during induction of the growth response and tumorigenesis may be accounted for by promoter-specific activation and repression mediated by regional differences in Jun family proteins.
Cancer Res 1993 Aug 15
PMID:Promoter-specific trans-activation and inhibition mediated by JunB. 833 92

The UVB (290-320 nm) portion of the solar spectrum possesses the highest activity for the induction of skin cancer and has the capacity to stimulate epidermal proliferation. We report that UVB is a transcriptional inducer of the c-fos protooncogene in mouse JB6 epidermal cells. Induction is biphasic with an immediate early peak at 30-60 min and a second broader peak 8 h following irradiation. The immediate early phase is suppressed by inhibitors of nuclear adenosine diphosphoribose transferase. For UVB induction, the formation of full-length messages is less efficient than of early, short messages, while both types of messages are produced at similar rates following serum stimulation. Experiments with stable transfectants with reporter constructs linked to 5'-upstream sequences of c-fos indicate that UVB and serum stimulation both require the sequences from -345 to -285 which contain the joint DSE-AP-1 enhancer motifs for efficient induction. Mobility shift data reveal that the complement of c-Fos and c-Jun proteins which bind to the fos-AP-1 octanucleotide decrease immediately following irradiation. Increased binding of Fos and Jun is observed 8-24 h later. UVB did not cause an observable change in the nuclear proteins which bind to the dyad symmetry element oligonucleotide in vitro. Fos protein was detected among the binding proteins. We propose that the two phases of UVB-induced c-fos expression occur by quite different mechanisms. The immediate early phase is inhibited by adenosine diphosphoribose transferase inhibitors because poly-ADP ribosylation of chromosomal proteins is required for the resealing of UVB-induced DNA strand breaks which otherwise retard message elongation. The production of an autocrine factor may be responsible for the late phase of c-fos induction.
Cancer Res 1993 Jan 01
PMID:Mechanism of induction of c-fos by ultraviolet B (290-320 nm) in mouse JB6 epidermal cells. 841 48

Transgenic mice overexpressing the c-fos proto-oncogene in bone develop osteosarcomas, whereas mice overexpressing c-Jun are normal. In this study, we investigated whether Fos and Jun would cooperate in vivo and whether the threshold levels of Fos are important in osteosarcoma formation. Fos-Jun double-transgenic mice develop osteosarcomas at a higher frequency than single-Fos transgenic mice with no differences in the time of onset of tumor formation. Histological and histochemical analyses indicated that Fos-Jun tumors contained greater quantities of neoplastic bone, were more remodeled, and contained a greater number of multinucleated osteoclast-like cells than tumors isolated from age-matched, single transgenic littermates. In contrast, overexpression of Fos in knockout mice that lack endogenous Fos resulted in a decrease in the number of tumor-bearing mice; osteosarcomas were almost absent in c-fos -/- mice, whereas tumor incidence was reduced to approximately 50% in c-fos +/- mice. Cell lines isolated from Fos-Jun transgenic tumors expressed high levels of both transgenes but significantly lower levels of the jun-related gene junB compared with cells expressing only a c-fos transgene. Osteoblastic marker genes were expressed at varying levels in different cell lines, but expression of interstitial collagenase (matrix metalloproteinase-1) was enhanced in cells derived from Fos-Jun tumors. These studies demonstrate that coexpression of a c-jun transgene can enhance Fos-induced oncogenesis in vivo and suggest that a critical level of Fos is necessary for osteosarcoma development.
Cancer Res 1995 Dec 15
PMID:c-fos-induced osteosarcoma formation in transgenic mice: cooperativity with c-jun and the role of endogenous c-fos. 852 21


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