FOS／JUN介导佛波酯对内皮素基因表达的诱导作用

利用凝胶电泳迁移率改变实验、RNA印迹和蛋白质印迹分析分别检查了c-jun抗体对内皮素-1(ET-1)基因AP-1位点与核蛋白结合的影响及肿瘤促进剂佛波酯(TPA)对c-fos/c-jun基因表达的作用.结果发现,c-jun抗体可使AP-1位点-核蛋白复合物的电泳迁移率发生改变,TPA显著促进c-fos/c-jun基因表达和血管内皮细胞的AP-1结合活性.实验表明,TPA对ET-1基因表达的诱导作用是通过促进AP-1转录因子c-fos/c-jun合成来介导的.     

佛波酯诱导内皮素和FOS／JUN基因在血管内皮细胞中的表达及AP－1结合活性

佛波酯诱导内皮素和ＦＯＳ／ＪＵＮ基因在血管内皮细胞中的表达及ＡＰ－１结合活性温进坤,魏素珍（河北医学院生化教研室,石家庄０５００１７）张晨晖,姚阿卿,周爱儒,汤健（北京医科大学心血管基础研究所,北京,１０００８３）关键词内皮素基因表达;ＡＰ－１转录因...     

Regulation of c-jun and jun-B by progestins in T-47D human breast cancer cells.

To investigate further the molecular mechanisms of progestin regulation of human breast cancer cell growth, we studied the effect of progestins on expression of the protooncogene c-jun and other members of the jun family, jun-B and jun-D, in T-47D human breast cancer cells. The progestin medroxyprogesterone acetate (MPA) increased c-jun mRNA levels in a time- and dose-dependent fashion. Maximal effects were seen after 3 h of treatment with 10-100 nM MPA. Under these conditions, the c-jun mRNA was increased 5.4-fold above the control level. Although the c-jun mRNA level was increased by cycloheximide alone, a further 2.4-fold increase was seen when the cells were treated with MPA in the presence of cycloheximide. The p39 c-jun protein was also increased 3.8-fold by this treatment. Maximum levels of p39 c-jun protein were achieved 9 h after treatment, and this level was maintained for at least 24 h. Dexamethasone and dihydrotestosterone did not increase the p39 c-jun protein level under these conditions. However, MPA treatment of T-47D cells resulted in a 55% decrease in overall AP-1 activity, as measured by transient transfection of an AP-1-regulated chloramphenicol acetyltransferase reporter gene. These effects were all reversible by cotreatment with a 10-fold higher concentration of the antiprogestin RU 486. MPA decreased jun-B mRNA levels 50% 1 h after treatment in T-47D cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

Rapid and preferential activation of the c-jun gene during the mammalian UV response.

Exposure of mammalian cells to DNA-damaging agents leads to activation of a genetic response known as the UV response. Because several previously identified UV-inducible genes contain AP-1 binding sites within their promoters, we investigated the induction of AP-1 activity by DNA-damaging agents. We found that expression of both c-jun and c-fos, which encode proteins that participate in formation of the AP-1 complex, is rapidly induced by two different DNA-damaging agents: UV and H2O2. Interestingly, the c-jun gene is far more responsive to UV than any other immediate-early gene that was examined, including c-fos. Other jun and fos genes were only marginally affected by UV or H2O2. Furthermore, UV is a much more efficient inducer of c-jun than phorbol esters, the standard inducers of c-jun expression. This preferential response of the c-jun gene is mediated by its 5' control region and requires the TPA response element, suggesting that this element also serves as an early target for the signal transduction pathway elicited by DNA damage. Both UV and H2O2 lead to a long-lasting increase in AP-1 binding activity, suggesting that AP-1 may mediate the induction of other damage-inducible genes such as human collagenase.     

Suppression of albumin enhancer activity by H-ras and AP-1 in hepatocyte cell lines.

We demonstrated, using a transient transfection assay, that the albumin enhancer increased the expression of the albumin promoter in a highly differentiated, simian virus 40 (SV40)-immortalized hepatocyte cell line, CWSV1, but was not functional in two ras-transformed cell lines (NR3 and NR4) derived from CWSV1 by stable transfection with the T24ras oncogene. A transient cotransfection assay showed that T24ras and normal c-Ha-ras were each able to inhibit the activity of the albumin enhancer in an immortal hepatocyte cell line. DNase I footprinting and gel mobility shift assays demonstrated that the DNA binding activities specific to the albumin enhancer were not decreased in the ras-transformed cells. ras also did not diminish the expression of HNF1 alpha, C/EBP alpha, HNF3 alpha, HNF3 beta, or HNF3 gamma but did significantly increase AP-1 binding activity. Three AP-1 binding sites were identified within the albumin enhancer, and DNA binding activities specific to these AP-1 sites were induced in the ras-transformed hepatocytes. Subsequent functional assays showed that overexpression of c-jun and c-fos inhibited the activity of the albumin enhancer. Site-directed mutagenesis of the AP-1 binding sites in the albumin enhancer partially abrogated the suppressing effect of ras and c-jun/c-fos on the enhancer. These functional studies therefore supported the results of the structural studies with AP-1. We conclude that the activity of the albumin enhancer is subject to regulation by ras signaling pathways and that the effect of ras on the albumin enhancer activity may be mediated by AP-1.     

Hydrogen peroxide-induced expression of the proto-oncogenes, c-jun, c-fos and c-myc in rabbit lens epithelial cells

The involvement of H2O2 in cataract development has been established inboth human patients and animal models. At the molecular level H2O2 has beenobserved to cause damage to DNA, protein and lipid. To explore the oxidativestress response of the lens system at the gene expression level, we haveexamined the effects of H2O2 on the mRNA change of the proto-oncogenes,c-jun, c-fos and c-myc in a rabbit lens cell line, N/N1003A. H2O2 treatmentof the rabbit lens epithelial cells for 60 min induces quick up-regulationof both c-jun and c-fos mRNAs. The maximal induction is 38 fold for c-jun at150 µM and 72 fold for c-fos at 250 µM H2O2. Treatment ofN/N1003A cells with 50-250 µM H2O2 for 60 min leads to a 2-5 foldincrease of the c-myc mRNA level. H2O2 also induces an up-regulation intransactivity of the activating protein-1 (AP-1) as shown with a reportergene driven by a prolactin gene promoter with 4 copies of AP-1 binding sitesinserted in the upstream of the promoter. Maximal induction occurs with 150µM H2O2. In the same system, the antioxidants, N-acetyl-cysteine (NAC)and pyrrolidine dithiocarbamate (PDTC) at concentrations shown toup-regulate the mRNAs of both c-jun and c-fos, also enhance thetransactivity of AP-1. NAC and PDTC have different effects in modulating theinduction of AP-1 activity by H2O2 and TPA. These results reveal thatoxidative stress regulates expression of various regulatory genes in lenssystems, which likely affects cell proliferation, differentiation andviability and thus affect normal lens functions.     

trans-repression of the mouse c-fos promoter: a novel mechanism of Fos-mediated trans-regulation

Fos protein can trans-activate AP-1-dependent gene expression and trans-repress the c-fos promoter. Although we find that trans-repression is enhanced by coexpression of c-Jun, it does not require any of the AP-1 or ATF sites in the mouse c-fos promoter. A major target for repression is the serum response element (SRE). Fos mutants with an impaired leucine zipper are defective in trans-repression and transformation, suggesting that these functions involve the formation of Fos protein complexes. In contrast, mutations that abolish DNA binding of Fos enhance trans-repression but destroy the transforming potential of Fos. In addition, v-Fos protein efficiently transforms but is unable to trans-repress. These findings point to different mechanisms involved in trans-activation and trans-repression and suggest that trans-repression of the type described here is neither sufficient nor required for Fos-induced transformation.     

Suppression of glutathione transferase P expression by glucocorticoid.

A strong enhancer element, GPEI, of the glutathione transferase P gene (GST-P) gene is composed of two phorbol 12-O-tetradecanoate 13-acetate (TPA) responsive element (TRE)-like sequences at opposite orientation. Unlike TRE sequences of other genes, GPEI exhibits a strong enhancer activity in F9 cells, which contains little AP-1. GPEI bound to AP-1 In vitro and GST-P expression was activated by TPA and exogenously introduced c-jun gene in a rat fibroblast cell line. Both the stimulated expression of GST-P gene by TPA and that by over-expressed c-Jun were suppressed to the basal level by dexamethasone, an inhibitor of AP-1. Basal expression of GST-P gene, however, was not inhibited by dexamethasone. Transfected chloramphenicol acetyltransferase (CAT) gene having GPEI also behaved as the endogenous GST-P gene. These results indicate that the GPEI is activated by AP-1 but constitutive activity of this enhancer in a rat fibroblast cell line 3Y1 cells is due to some unknown mechanism other than AP-1.     

The human T-lymphotropic virus type I tax gene can cooperate with the ras oncogene to induce neoplastic transformation of cells.

Epidemiologic studies have linked infection by the human T-lymphotropic virus type I (HTLV-I) with the development of adult T-cell leukemia. The low penetrance of the virus and the long latency for disease manifestation are factors that obscure the role of HTLV-I infection in oncogenesis. We have used an in vitro transformation assay system to determine directly whether the HTLV-I tax gene has transformation potential. Transfection of the tax gene alone into early-passage rat embryo fibroblasts did not induce morphological alterations. However, cotransfection of tax with the selectable marker plasmid pRSVneo gave rise to G418-resistant colonies that could be established as immortalized cell lines. Cotransfection of tax with the ras oncogene into rat embryo fibroblasts gave rise to foci of transformed cells that were highly tumorigenic in nude mice. These data represent a direct demonstration of the oncogenic potential of the tax gene in nonlymphoid cells and establish HTLV-I as a transforming virus.