Differential regulation of IL-6 promoter activity in a human ovarian-tumor cell line transfected with various p53 mutants: involvement of AP-1

Single nucleotide polymorphism of transforming growth factor-β1 and interleukin-6 as risk factors for ovarian cancer

INTRODUCTION

We investigated the association between common variants in TGF-β1, IL-6 and the risk of ovarian cancer (OC) in Tunisian patients and control women.

MATERIAL METHODS AND RESULTS

Study subjects comprised 71 OC cases and 74 control women. Genotyping of TGF-β1 and IL-6 SNPs was done by real-time PCR. No differences were noted in the minor allele frequencies of the three TGF-β1 SNPs between OC patients and controls. However, marked differences in the distribution of TGF-β1 rs1800469 genotypes were seen between OC cases and controls (p < 0.001), with TGF-β1 rs1800469 heterozygous (C/T) genotype being negatively associated with OC (OR [95% CI] = 0.24 [0.15-0.58]). The allelic and genotypic distributions at IL-6 polymorphisms showed a positive association between minor allele (G) at IL-6 rs1880242 variant (p = 0.0275; R [95% CI] = 1.88 [1.03-3.46]) and the occurrence of OC. In fact, the presence of T allele [G/T + T/T] decrease the risk of OC (p = 0.021; OR [95% CI] = 0.38 [0.17-0.88]). In addition, the Haploview analysis demonstrated high linkage disequilibrium (LD) between IL-6 SNPs and eight-locus haplotype analysis identified that GGAGGGGA and GGAGGGTA haplotypes are positively associated with OC risk. A negative association was shown between IL-6 haplotype (TGGGCCTA) and OC occurrence.

CONCLUSIONS

Our results suggest that TGF-β1 rs1800469, IL-6 rs1880242 variants and IL-6 haplotype (TGGGCCTA) have protective roles of OC risk. IL-6 haplotypes (GGAGGGGA and GGAGGGTA) increase OC susceptibility among Tunisian women.

IκB-Kinase-epsilon (IKKε) over-expression promotes the growth of prostate cancer through the C/EBP-β dependent activation of IL-6 gene expression

The inflammatory cytokine IL-6 has been shown to induce the nuclear translocation of androgen receptors in prostate cancer cells and to activate the androgen receptors in a ligand-independent manner, suggesting it may contribute to the development of a castrate-resistant phenotype. Elevated IL-6 serum levels have also been associated with metastasis-related morbidity in prostate cancer patients. We have previously established that over-expression of I-kappa-B-kinase-epsilon (IKKε also named IKKi or IκBKε) in hormone-sensitive prostate cancer cell lines induces IL-6 secretion. We have also reported that prostate cancer cell lines lacking androgen receptor expression exhibit high constitutive IKKε expression and IL-6 secretion. In the present study, we validated the impact of IKKε depletion on the in vitro proliferation of castrate-resistant prostate cancer cells, and characterized how IKKε depletion affects tumor growth and IL-6 tumor secretion in vivo through a mouse xenograft-based approach. We observed a significant growth delay in IKKε-silenced PC-3 cells injected in SCID mice fed with a doxycycline-supplemented diet in comparison with mice fed with a normal diet. We also found a decrease in IL-6 secretion levels that strongly correlated with tumor growth inhibition. Finally, using constructs with various IL-6-mutated promoters, we demonstrated that IKKε over-expression induces a NF-κB-independent stimulation of the IL-6 gene promoter through the activation and nuclear accumulation of the transcription factor C/EBP-β. Our study demonstrates the pro-proliferative role of the oncogene IKKε in castrate-resistant prostate cancer cell lines, involving the phosphorylation and nuclear translocation of C/EBP-β that initiates IL-6 gene expression.

IL-1β induces IL-6 production in retinal Müller cells predominantly through the activation of p38 MAPK/NF-κB signaling pathway

IL-6 plays an important role in various inflammatory ocular diseases, including diabetic retinopathy. Müller cells are the major source of inflammatory mediators, including IL-6, in the retina. However, the mechanism of regulating IL-6 production in these cells remains unclear. Examination of signaling pathways in human retinal Müller cells (MIO-M1 cell line) cultured with IL-1β, TNF-α, IL-6, IL-8, VEGF, IFN-γ, glucose or mannitol showed that IL-1β was the most potent stimulator of IL-6 production. In addition, IL-1 β also increased NF-κB p50 protein level and phosphorylation of p38 MAPK, ERK1/2 and c-Jun. Induction of IL-6 production by IL-1β was significantly reduced by addition of p38 MAPK (SB203580), MEK1/2 (U0126) or NF-κB (BAY11-7082) inhibitors, with the highest effect being observed with SB203580. To explore the specific elements in IL-6 promoter responsible for IL-1β-induction of IL-6 expression, a series of plasmids bearing various IL-6 promoter mutations were transiently expressed in MIO-MI cells cultured in the presence or absence of IL-1β (10ng/ml) and/or SB203580 (10µM). Results showed that IL-6 promoter activity of the parent pIL-6-Luc651 was significantly enhanced by IL-1β, but the level was significantly attenuated by SB203580. Furthermore, the IL-6 promoter activity was also reduced upon deletion of NF-κB, AP-1 or C/EBP binding sites, with NF-κB deletion being the greatest. These results are the first demonstration that IL-1β induces IL-6 production in Müller cells by activation of IL-6 promoter activity predominantly through the p38 MAPK/NF-κB pathway.

Targeting interleukin-6 in inflammatory autoimmune diseases and cancers

Interleukin-6 (IL-6) is a pleiotropic cytokine with significant functions in the regulation of the immune system. As a potent pro-inflammatory cytokine, IL-6 plays a pivotal role in host defense against pathogens and acute stress. However, increased or deregulated expression of IL-6 significantly contributes to the pathogenesis of various human diseases. Numerous preclinical and clinical studies have revealed the pathological roles of the IL-6 pathway in inflammation, autoimmunity, and cancer. Based on the rich body of studies on biological activities of IL-6 and its pathological roles, therapeutic strategies targeting the IL-6 pathway are in development for cancers, inflammatory and autoimmune diseases. Several anti-IL-6/IL-6 receptor monoclonal antibodies developed for targeted therapy have demonstrated promising results in both preclinical studies and clinical trials. Tocilizumab, an anti-IL-6 receptor antibody, is effective in the treatment of various autoimmune and inflammatory conditions notably rheumatoid arthritis. It is the only IL-6 pathway targeting agent approved by the regulatory agencies for clinical use. Siltuximab, an anti-IL-6 antibody, has been shown to have potential benefits treating various human cancers either as a single agent or in combination with other chemotherapy drugs. Several other anti-IL-6-based therapies are also under clinical development for various diseases. IL-6 antagonism has been shown to be a potential therapy for these disorders refractory to conventional drugs. New strategies, such as combination of IL-6 blockade with inhibition of other signaling pathways, may further improve IL-6-targeted immunotherapy of human diseases.

Transcriptional regulation of the gilthead seabream (Sparus aurata) interleukin-6 gene promoter

Interleukin-6 (IL-6) has been identified and characterized from several fish species and its mRNA expression is induced by pathogen-associated molecular patterns (PAMPs) and cytokines in immune cells and tissues. However, the transcriptional regulation of the IL-6 gene in fish is not well understood. In the present study, we have cloned and sequenced a 1028 bp 5'-flanking DNA region from the IL-6 gene in seabream (Sparus aurata). Sequence analysis of the seabream IL-6 promoter (sbIL-6P) evidenced the presence of a conserved TATA motif and conserved response elements for NF-κB, C/EBPβ (NF-IL6), AP-1 and GRE, similar to other vertebrate IL-6 promoters. Functional characterization of sbIL-6P was performed by cloning sbIL-6P into a luciferase expression vector and by transfecting it into L6 muscle cells, a mammalian cell line shown previously to express IL-6 in response to pro-inflammatory stimuli. We show here that the activity of sbIL-6P was significantly induced by pro-inflammatory cytokines such as tumor necrosis factor alpha (TNFα), IL-6 and IL-2, as well as by lipopolysaccharide (LPS), but significantly repressed by dexamethasone. In addition, the stimulatory effects of TNFα on sbIL-6P activity appeared to be mediated by the NF-κB, p38 MAPK and JNK signaling pathways. Deletion analyses of sbIL-6P suggested that activation of sbIL-6P by TNFα and IL-6 required the presence of binding motifs present in the proximal promoter (-171 to -84) whereas activation by IL-2 required binding motifs present in the distal promoter (-1024 to -864). The results from this study indicate, for the first time in fish, that pro-inflammatory cytokines, LPS and glucocorticoids can regulate the activity of the IL-6 gene at a transcriptional level and identify important regions in its response to cytokines.

Prognostic significance of IL-6 and IL-8 ascites levels in ovarian cancer patients

Background

The acellular fraction of epithelial ovarian cancer (EOC) ascites promotes de novo resistance of tumor cells and thus supports the idea that tumor cells may survive in the surrounding protective microenvironment contributing to disease recurrence. Levels of the pro-inflammatory cytokines IL-6 and IL-8 are elevated in EOC ascites suggesting that they could play a role in tumor progression.

Methods

We measured IL-6 and IL-8 levels in the ascites of 39 patients with newly diagnosed EOC. Commercially available enzyme-linked immunosorbent assay (ELISA) was used to determine IL-6 and IL-8 ascites levels. Ascites cytokine levels were correlated with clinicopathological parameters and progression-free survival.

Results

Mean ascites levels for IL-6 and IL-8 were 6419 pg/ml (SEM: 1409 pg/ml) and 1408 pg/ml (SEM: 437 pg/ml) respectively. The levels of IL-6 and IL-8 in ascites were significantly lower in patients that have received prior chemotherapy before the surgery (Mann-Whitney U test, P = 0.037 for IL-6 and P = 0.008 for IL-8). Univariate analysis revealed that high IL-6 ascites levels (P = 0.021), serum CA125 levels (P = 0.04) and stage IV (P = 0.009) were significantly correlated with shorter progression-free survival. Including these variables in a multivariate analysis revealed that elevated IL-6 levels (P = 0.033) was an independent predictor of shorter progression-free survival.

Conclusion

Elevated IL-6, but not IL-8, ascites level is an independent predictor of shorter progression-free survival.

Immuno-modulatory gene polymorphisms and outcome in breast and ovarian cancer

Breast and ovarian cancer continue to be a significant source of morbidity and mortality. Improved understanding of signalling pathways related to growth and apoptosis has led to targeted treatments and modest improvement in long term outcomes. However, it has become increasingly clear that tumor factors alone are not the sole determinants of outcome in patients with breast and ovarian cancer. The tumor microenvironment and other immunologic host processes play an integral role in the overall interactions between disease, host and treatment. Cytokines play a major role in the immune response to tumors. Single nucleotide polymorphisms (SNPs) in the regulatory or coding regions of many cytokine genes lead to functional alterations in the transcriptional regulation of these genes or the proteins they encode. This review examines the current literature linking functional variants in cytokine and other immune genes to outcomes in breast and ovarian cancer. We have focused on those involved in the proinflammatory response (IL-6, TNF-alpha), apoptosis (TGF-beta, Fas, FasL, C1QA), angiogenesis (IL-8) and autoimmunity (IL-10). While much remains to be learned about the mechanisms underlying these variants and their impact on tumor behavior, this area holds promise for future development of prognostic profiles and therapeutics exploiting the immune response.

The role of proto-oncogene Fra-1 in remodeling the tumor microenvironment in support of breast tumor cell invasion and progression

A growing body of evidence indicates that interactions between neoplastic cells and tumor-associated macrophages (TAMs) in the tumor microenvironment (TME) are crucial in promoting tumor cell invasion and progression. Macrophages play an ambiguous role in these processes since this M1 phenotype correlates with tumoricidal capacity whereas TAMs of M2 phenotype exert tumor-promoting effects. Here, we provide evidence that interactions between mouse breast tumor cells and TAMs remodel the TME, leading to upregulation of Fra-1, a member of the FOS family of transcription factor. In turn, this proto-oncogene initiates activation of the IL-6/JAK/Stat3 signaling pathway. This creates a malignant switch in breast tumor cells, leading to increased release of pro-angiogenic factors MMP-9, VEGF and TGF-β from tumor cells and intensified invasion and progression of breast cancer. Proof of concept for the crucial role played by transcription factor Fra-1 in regulating these processes was established by specific knockdown of Fra-1 with siRNA which resulted in marked suppression of tumor cell invasion, angiogenesis and metastasis in a mouse breast cancer model. Such a strategy could eventually lead to future efficacious treatments of metastatic breast cancer.

Over-expression of IkappaB-kinase-epsilon (IKKepsilon/IKKi) induces secretion of inflammatory cytokines in prostate cancer cell lines

BACKGROUND

Elevated inflammatory cytokine levels in serum have been associated with advanced stage metastasis-related morbidity in prostate cancer. Several studies have shown that IL-6 and IL-8 can accelerate the growth of human prostate cancer cell lines. Previous studies, in murine embryonic fibroblasts, have shown that Ikappa-B kinase-epsilon (IKKepsilon/IKKi)-deficiency results in the reduction of lipopolysaccharide-mediated expression of IL-6.

RESULTS

In this study, we report that over-expression of IKKepsilon in hormone-sensitive 22Rv1 and LNCaP prostate cancer cells induces the secretion of several inflammatory cytokines including IL-6 and IL-8. Both of these cytokines are secreted by hormone-refractory PC-3 prostate cancer cells and IKKepsilon knock-down in these cells correlates with a strong decrease in IL-6 secretion. Furthermore, we demonstrate that IKKepsilon over-expression does not induce the activation of the IKKepsilon classical targets NF-kappaB and IRF-3, two transcription factors involved in the regulation of several cytokines. Finally, we observe that high IKKepsilon expression results in its nuclear translocation, a phenomena that is TBK1-independent.

CONCLUSIONS

This study identifies IKKepsilon as a potential prostate cancer gene that may favor chronic inflammation and create a tumor-supporting microenvironment that promotes prostate cancer progression, particularly by the induction of IL-6 secretion that may act as a positive growth factor in prostate cancer.

Interleukin-6-producing undifferentiated thymic carcinoma with neuroendocrine features

Undifferentiated thymic carcinoma is a rare tumor of the thymus. Due to the extreme rarity of undifferentiated thymic carcinoma, very limited information about its characteristics is available. We encountered an autopsy case of a 33-year-old woman diagnosed as having an undifferentiated thymic carcinoma with a high inflammatory response. The patient's serum interleukin-6 (IL-6) was elevated to 1930 pg/ml, and immunohistochemical staining of the carcinoma cells was positive for neuroendocrine markers and IL-6. To the best of our knowledge, this is the first report of an IL-6-producing undifferentiated thymic carcinoma with neuroendocrine features that shows a novel potential to produce IL-6.

JunB is required for IgE-mediated degranulation and cytokine release of mast cells

Mast cells are effector cells of IgE-mediated immune responses frequently found at the vicinity of blood vessels, the margins of diverse tumors and at sites of potential infection and inflammation. Upon IgE-mediated stimulation, mast cells produce and secrete a broad spectrum of cytokines and other inflammatory mediators. Recent work identified JunB, a member of the AP-1 transcription factor family, as critical regulator of basal and induced expression of inflammatory mediators in fibroblasts and T cells. To study the impact of JunB on mast cell biology, we analyzed JunB-deficient mast cells. Mast cells lacking JunB display a normal in vivo maturation, and JunB-deficient bone marrow cells in vitro differentiated to mast cells show no alterations in proliferation or apoptosis. But these cells exhibit impaired IgE-mediated degranulation most likely due to diminished expression of SWAP-70, Synaptotagmin-1, and VAMP-8, and due to impaired influx of extracellular calcium. Moreover, JunB-deficient bone marrow mast cells display an altered cytokine expression profile in response to IgE stimulation. In line with these findings, the contribution of JunB-deficient mast cells to angiogenesis, as analyzed in an in vitro tube formation assay on matrigel, is severely impaired due to limiting amounts of synthesized and secreted vascular endothelial growth factor. Thus, JunB is a critical regulator of intrinsic mast cell functions including cross-talk with endothelial cells.

Interleukin-6 and its receptor in cancer: implications for translational therapeutics

Interleukin-6 (IL-6) plays a major role in the response to injury or infection and is involved in the immune response, inflammation, and hematopoiesis. Its deregulation impacts numerous disease states, including many types of cancer. Consequently, modulating IL-6 may be an innovative therapeutic strategy in several diseases. A review of relevant published literature regarding IL-6 and its receptor was performed. In addition, a review of the relevance of this cytokine system to human illness, particularly in cancer, was undertaken. IL-6 is a pleiotropic cytokine that is involved in the physiology of virtually every organ system. Aberrant expression of this cytokine has been implicated in diverse human illnesses, most notably inflammatory and autoimmune disorders, coronary artery and neurologic disease, gestational problems, and neoplasms. In cancer, high levels of circulating IL-6 are observed in almost every type of tumor studied and predict a poor outcome. Furthermore, elevated IL-6 levels are associated strongly with several of the striking phenotypic features of cancer. Several molecules have been developed recently that target the biologic function of IL-6. Early results in the clinic suggest that this strategy may have a significant salutary impact on diverse tumors. The field of cytokine research has yielded a deep understanding of the fundamental role of IL-6 and its receptor in health and disease. Therapeutic targeting of IL-6 and its receptor in cancer has strong biologic rationale, and there is preliminary evidence suggesting that targeting of the IL-6 system may be beneficial in the treatment of cancer.

Tumor necrosis factor alpha (TNFalpha) stimulates Map4k4 expression through TNFalpha receptor 1 signaling to c-Jun and activating transcription factor 2

Tumor necrosis factor alpha (TNFalpha) is a cytokine secreted by macrophages and adipocytes that contributes to the low grade inflammation and insulin resistance observed in obesity. TNFalpha signaling decreases peroxisome proliferator-activated receptor gamma and glucose transporter isoform 4 (GLUT4) expression in adipocytes, impairing insulin action, and this is mediated in part by the yeast Ste20 protein kinase ortholog Map4k4. Here we show that Map4k4 expression is selectively up-regulated by TNFalpha, whereas the expression of the protein kinases JNK1/2, ERK1/2, p38 stress-activated protein kinase, and mitogen-activated protein kinase kinases 4/7 shows little or no response. Furthermore, the cytokines interleukin 1beta (IL-1beta) and IL-6 as well as lipopolysaccharide fail to increase Map4k4 mRNA levels in cultured adipocytes under conditions where TNFalpha elicits a 3-fold effect. Using agonistic and antagonistic antibodies and small interfering RNA (siRNA) against TNFalpha receptor 1 (TNFR1) and TNFalpha receptor 2 (TNFR2), we show that TNFR1, but not TNFR2, mediates the increase in Map4k4 expression. TNFR1, but not TNFR2, also mediates a potent effect of TNFalpha on the phosphorylation of JNK1/2 and p38 stress-activated protein kinase and their downstream transcription factor substrates c-Jun and activating transcription factor 2 (ATF2). siRNA-based depletion of c-Jun and ATF2 attenuated TNFalpha action on Map4k4 mRNA expression. Consistent with this concept, the phosphorylation of ATF2 along with the expression and phosphorylation of c-Jun by TNFalpha signaling was more robust and prolonged compared with that of IL-1beta, which failed to modulate Map4k4. These data reveal that TNFalpha selectively stimulates the expression of a key component of its own signaling pathway, Map4k4, through a TNFR1-dependent mechanism that targets the transcription factors c-Jun and ATF2.

A critical role for p53 in the control of NF-kappaB-dependent gene expression in TLR4-stimulated dendritic cells exposed to Genistein

Considerable research has focused on the anti-inflammatory and antiproliferative activities exhibited by the soy isoflavone genistein. We previously demonstrated that genistein suppresses TNF-alpha-induced NF-kappaB-dependent IL-6 gene expression in cancer cells by interfering with the mitogen- and stress-activated protein kinase 1 activation pathway. However, effects of isoflavones on immune cells, such as dendritic cells, remain largely unknown. Here we show that genistein markedly reduces IL-6 cytokine production and transcription in LPS-stimulated human monocyte-derived dendritic cells. More particularly, we observe that genistein inhibits IL-6 gene expression by modulating the transcription factor NF-kappaB. Examination of NF-kappaB-related events downstream of TLR4 demonstrates that genistein affects NF-kappaB subcellular localization and DNA binding, although we observe only a minor inhibitory impact of genistein on the classical LPS-induced signaling steps. Interestingly, we find that genistein significantly increases p53 protein levels. We also show that overexpression of p53 in TLR4/MD2 HEK293T cells blocks LPS-induced NF-kappaB-dependent gene transcription, indicating the occurrence of functional cross-talk between p53 and NF-kappaB. Moreover, analysis of IL-6 mRNA levels in bone marrow-derived p53 null vs wild-type dendritic cells confirms a role for p53 in the reduction of NF-kappaB-dependent gene expression, mediated by genistein.

c-Fos as a regulator of degranulation and cytokine production in FcepsilonRI-activated mast cells

The AP-1 complex is composed of c-Jun and c-Fos and is a key component in the regulation of proinflammatory genes. Mast cells play a significant role in the initiation of many inflammatory responses, such as allergy and allergy-associated diseases. In the present work, we characterized the role of c-Fos in mast cell function by investigating IL-3-dependent cell proliferation, degranulation capability, and cytokine expression in c-Fos-deficient mice. In c-Fos-deficient mast cells, we found that FcepsilonRI-mediated degranulation was significantly inhibited, which correlates with the reduced expression of SWAP-70, VAMP-7, and Synaptotagmin I genes, which are involved directly in the degranulation process. These findings show that c-Fos plays an important role in FcepsilonRI-mediated regulation of mast cell function.

Tumor-derived p53 mutants induce oncogenesis by transactivating growth-promoting genes

We have studied the mechanism of mutant p53-mediated oncogenesis using several tumor-derived mutants. Using a colony formation assay, we found that the majority of the mutants increased the number of colonies formed compared to the vector. Expression of tumor-derived p53 mutants increases the rate of cell growth, suggesting that the p53 mutants have 'gain of function' properties. We have studied the gene expression profile of cells expressing tumor-derived p53-D281G to identify genes transactivated by mutant p53. We report the transactivation of two genes, asparagine synthetase and human telomerase reverse transcriptase. Quantitative real-time PCR confirms this upregulation. Transient transfection promoter assays verify that tumor-derived p53 mutants transactivate these promoters significantly. An electrophoretic mobility shift assay shows that tumor-derived p53-mutants cannot bind to the wild-type p53 consensus sequence. The results presented here provide some evidence of a possible mechanism for mutant p53-mediated transactivation.

Inhibition of p53 function diminishes androgen receptor-mediated signaling in prostate cancer cell lines

Current therapy for advanced prostate cancer is mainly based on androgen deprivation, although most patients relapse to androgen-insensitive disease. Several mechanisms contributing to androgen-independent growth including alterations in the structure or expression of the androgen receptor (AR) and its cofactors have been identified. Recent evidence suggests that p53 is involved in androgen signaling. The analysis of the effect of p53 on androgen signaling was performed in 22Rv1 and LNCaP prostate cancer cells that express both p53 and AR. The overexpression of p53 diminished the androgenic response in both cell lines in a reporter gene assay. Conversely, the inhibition of p53 by three different p53 inhibitors, Pifithrin-1alpha (PFT-1alpha), an inhibitor of p53-dependent transactivation; MDM2, a regulator of p53 expression; and a dominant-negative N-terminally truncated p53 gene also reduced transactivation of androgen-dependent reporter genes. The inactivation of p53 by PFT-1alpha decreased AR-protein expression in both 22Rv1 and LNCaP cells. Our findings confirm that the overexpression of wild-type p53 decreases androgen function, whereas p53 expression at physiological levels stabilizes AR signaling. Thus, our findings suggest that there is a balance of AR and p53 expression during the androgen-dependent growth of prostate cancer, which is obliterated during further progression of the disease.

JunD regulates transcription of the tissue inhibitor of metalloproteinases-1 and interleukin-6 genes in activated hepatic stellate cells

Activation of hepatic stellate cells (HSCs) to a myofibroblast-like phenotype is the pivotal event in hepatic wound healing and fibrosis. Rat HSCs activated in vitro express JunD, Fra2, and FosB as the predominant AP-1 DNA-binding proteins, and all three associate with an AP-1 sequence that is essential for activity of the tissue inhibitor of metalloproteinases-1 (TIMP-1) promoter. In this study, we used expression vectors for wild-type, dominant-negative, and forced homodimeric (Jun/eb1 chimeric factors) forms of JunD and other Fos and Jun proteins to determine the requirement for JunD in the transcriptional regulation of the TIMP-1 and interleukin-6 (IL-6) genes. JunD activity was required for TIMP-1 gene promoter activity, whereas overexpression of Fra2 or FosB caused a repression of promoter activity. The ability of homodimeric JunD/eb1 to elevate TIMP-1 promoter activity supports a role for JunD homodimers as the major AP-1-dependent transactivators of the TIMP-1 gene. IL-6 promoter activity was induced upon activation of HSCs and also required JunD activity; however, expression of JunD/eb1 homodimers resulted in transcriptional repression. Mutagenesis of the IL-6 promoter showed that an AP-1 DNA-binding site previously reported to be an activator of transcription in fibroblasts functions as a suppressor of promoter activity in HSCs. We conclude that JunD activates IL-6 gene transcription as a heterodimer and operates at an alternative DNA-binding site in the promoter. The relevance of these findings to events occurring in the injured liver was addressed by showing that AP-1 DNA-binding complexes are induced during HSC activation and contain JunD as the predominant Jun family protein. JunD is therefore an important transcriptional regulator of genes responsive to Jun homo- and heterodimers in activated HSCs.

p53 down-regulates human bradykinin B1 receptor gene expression

The tumor suppressor, p53, has been shown to transcriptionally activate or silence a number of target genes. As an activator, p53 relies on its specific consensus sequence within the promoter. It is not clear whether p53 requires a specific DNA binding site in its action as a gene repressor. This report demonstrates that the human BKB1R gene is a p53 target. Expression of p53 in transiently transfected SV40-transformed IMR90 cells strongly suppressed luciferase reporter activity driven by a 1.8 kb BKB1R promoter as well as its minigene. These down-regulations were p53 dose-dependent. p53 reduced both basal and induced promoter activities of the minigene. Expression of p53 abolished the inducibility of the minigene. Induction of endogenous p53 expression by etoposide also inhibited promoter activity and minigene inducibility. Replacing the region containing both the putative p53 binding site and the TATA-box with a basal adenovirus promoter in the 1.8 kb promoter construct did not prevent p53 from inhibiting BKB1R promoter activity. Thus suppression by p53 is not mediated by competition with the TATA-binding protein and is not through interaction with the putative p53-binding site. p53 also does not appear to suppress BKB1R gene expression through interaction with c-Jun which functions in the inducibility of this gene [Yang et al., 2001].

deltaFosB: a molecular switch underlying long-term neural plasticity

Numerous chronic perturbations have been shown to induce highly stable isoforms of the transcription factor deltaFosB in the brain in a region-specific manner. This review examines the functional consequences of the induction of deltaFosB in particular neuronal populations as well as its possible role in behavioral abnormalities such as drug addiction and movement disorders.

Interferon-alpha synergistically enhances induction of interleukin-6 by double stranded RNA in HeLa cells

Double stranded RNA (dsRNA), an intermediate that is common during viral infection, directly induces much higher levels of expression of interleukin-6 (IL-6) mRNA than does the cytokine IL-1beta. Interferon alpha (IFNalpha) by itself does not induce expression of IL-6; nonetheless, IFNalpha pretreatment dramatically enhances IL-6 induction by dsRNA but not by IL-1beta. Mutation of either the activating transcription factor/cyclic AMP response element binding protein (ATF/CREB) or the NF-IL-6 binding element within the IL-6 promoter eliminates most responsiveness of CAT reporter constructs to either dsRNA or to IL-1beta. IFNalpha pretreatment partially restores responsiveness to dsRNA but not to IL-1beta when either the ATF/CREB site or the NF-IL-6 site is mutated, but at least one of these sites must be intact for responsiveness to be restored. Mutation of the kappaB binding site in the IL-6 promoter eliminates responsiveness to either IL-1beta or to dsRNA, and pretreatment with IFNalpha does not restore any responsiveness. Incubation with dsRNA leads to a decrease in protein translation, especially in cells that have been pretreated with IFNalpha. Nonetheless, IFNalpha pretreatment followed by dsRNA leads to very high IL-6 protein levels. These studies demonstrate that major differences exist in the induction of IL-6 at both the mRNA and protein levels by dsRNA compared to cytokines and that IFNalpha pretreatment selectively enhances IL-6 induction by dsRNA but not by IL-1beta. The high levels of IL-6 expression that result when cells encounter class I IFN prior to dsRNA suggest a mechanism for a heightened host response to viral infection with heightened production of this pleotropic cytokine.

p53 down-regulates ER-responsive genes by interfering with the binding of ER to ERE

Overexpression of the tumor suppressor p53 in HeLa cells leads to loss of the estradiol- and genistein-induced human estrogen receptor (ERalpha) transactivity. The coactivator p300, which binds to both ERalpha and p53, does not prevent this loss of hERalpha function. In this report we demonstrate that p53 physically binds to multiple domains of the hERalpha. This binding did not interfere with either the ERalpha dimerization or the interaction between hERalpha and its coactivator SRC-1. However, p53 did interfere with the hERalpha-ERE binding. These results may explain how p53 down-regulates the expression of some estrogen-responsive genes such as c-fos, c-jun, TPA, and bcl-2. This study supports the cross-talk between the p53 and the ERalpha signaling pathways.