Triple synergism of human T-lymphotropic virus type 1-encoded tax, GATA-binding protein, and AP-1 is required for constitutive expression of the interleukin-5 gene in adult T-cell leukemia cells

Role of Fra-2 in cancer

Fos-related antigen-2 (Fra-2) is the most recently discovered member of the Fos family and, by dimerizing with Jun proteins, forms the activator protein 1 (AP-1) transcription factor. By inducing or repressing the transcription of several target genes, Fra-2 is critically involved in the modulation of cell response to a variety of extracellular stimuli, stressors and intracellular changes. In physiological conditions, Fra-2 has been found to be ubiquitously expressed in human cells, regulating differentiation and homeostasis of bone, muscle, nervous, lymphoid and other tissues. While other AP-1 members, like Jun and Fos, are well characterized, studies of Fra-2 functions in cancer are still at an early stage. Due to the lack of a trans-activating domain, which is present in other Fos proteins, it has been suggested that Fra-2 might inhibit cell transformation, eventually exerting an anti-tumor effect. In human malignancies, however, Fra-2 activity is enhanced (or induced) by dysregulation of microRNAs, oncogenes and extracellular signaling, suggesting a multifaceted role. Therefore, Fra-2 can promote or prevent transformation, proliferation, migration, epithelial-mesenchymal transition, drug resistance and metastasis formation in a tumor- and context-dependent manner. Intriguingly, recent data reports that Fra-2 is also expressed in cancer associated cells, contributing to the intricate crosstalk between neoplastic and non-neoplastic cells, that leads to the evolution and remodeling of the tumor microenvironment. In this review we summarize three decades of research on Fra-2, focusing on its oncogenic and anti-oncogenic effects in tumor progression and dissemination.

Does HTLV-1 Infection Show Phenotypes Found in Sjögren's Syndrome?

Viruses are a possible cause for Sjögren's syndrome (SS) as an environmental factor related to SS onset, which exhibits exocrine gland dysfunction and the emergence of autoantibodies. Although retroviruses may exhibit lymphocytic infiltration into exocrine glands, human T-cell leukemia virus type 1 (HTLV-1) has been postulated to be a causative agent for SS. Transgenic mice with HTLV-1 genes showed sialadenitis resembling SS, but their phenotypic symptoms differed based on the adopted region of HTLV-1 genes. The dominance of tax gene differed in labial salivary glands (LSGs) of SS patients with HTLV 1-associated myelopathy (HAM) and adult T-cell leukemia. Although HTLV-1 was transmitted to salivary gland epithelial cells (SGECs) by a biofilm-like structure, no viral synapse formation was observed. After infection to SGECs derived from SS patients, adhesion molecules and migration factors were time-dependently released from infected SGECs. The frequency of the appearance of autoantibodies including anti-Ro/SS-A, La/SS-B antibodies in SS patients complicated with HAM is unknown; the observation of less frequent ectopic germinal center formation in HTLV-1-seropositive SS patients was a breakthrough. In addition, HTLV-1 infected cells inhibited B-lymphocyte activating factor or C-X-C motif chemokine 13 through direct contact with established follicular dendritic cell-like cells. These findings show that HTLV-1 is directly involved in the pathogenesis of SS.

GATA binding protein 4 promotes the expression and transcription of hepatitis B virus by facilitating hepatocyte nuclear factor 4 alpha in vitro

Background

GATA binding protein 4 (GATA4) has been reported as a potential target of gene therapy for hepatocellular carcinoma (HCC). It is well known that the main cause of HCC is the chronic infection of hepatitis B virus (HBV). However, whether the effect of GATA4 on HBV has not yet been reported.

Methods

In this study, the regulation of GATA4 on HBV was analyzed in vitro. In turn, the effect of HBV on GATA4 was also observed in vitro, in vivo, and clinical HCC patients. Subsequently, we analyzed whether the effect of GATA4 on HBV was related to hepatocyte nuclear factor 4 alpha (HNF4α) in vitro.

Results

The results showed that GATA4 significantly promoted the secretion of HBV surface antigen (HBsAg) and HBV e antigen in the cell culture medium, improved the replication of HBV genomic DNA, and increased the level of HBV 3.5 kb pre-genomic RNA and HBV total RNA (P < 0.05). Moreover, it was showed that HBV had no significant effect on GATA4 in vitro and in vivo (P > 0.05). At the same time, GATA4 expression was decreased in 78.9% (15/19) of HCC patients regardless of the HBV and HBsAg status. Among them, there were 76.9% (10/13) in HBV-associated patients with HCC (HBV-HCC), and 83.3% (5/6) in non-HBV-HCC patients. In addition, the expression of HNF4α was also up-regulated or down-regulated accordingly when stimulating or interfering with the expression of GATA4. Furthermore, stimulating the expression of HNF4α could only alleviate the HBsAg level and HBV transcription levels, but had no significant effect on GATA4.

Conclusions

In summary, this study found that GATA4 has a positive effect on HBV, and the potential pathway may be related to another transcription factor HNF4α that regulates HBV.

Lymphoproliferative disorders associated with hypereosinophilia

Hypereosinophilia, defined as peripheral blood eosinophil counts > 1,500/μL, may complicate the course of various lymphoproliferative disorders. Among these, Hodgkin lymphoma (HL) and certain peripheral T-cell lymphomas (PTCLs) derived from CD4 cells, including Sezary syndrome (SS), adult T-cell leukemia/lymphoma (ATLL), and angioimmunoblastic T-cell lymphoma (AITL), are most commonly associated with increased reactive eosinophilopoiesis. Rarely, marked hypereosinophilia (HE) may occur in the setting of acute B-cell lymphoblastic leukemia, with a substantial impact on disease course. The mechanisms leading to blood and tissue eosinophilia in the setting of lymphoproliferative disorders, as well as the clinical complications and prognostic implications of hypereosinophilia, are discussed in this review.

Eosinophilic inflammation: mechanisms regulating IL-5 transcription in human T lymphocytes

BACKGROUND

Interleukin (IL)-5 is a key regulator of eosinophilia in allergic inflammation and parasite infections but the mechanisms regulating IL-5 expression in activated human T lymphocytes are poorly understood. From studies on mouse cells, the activation protein (AP)-1 and GATA-3 sites in the proximal promoter region appear to be important in IL-5 regulation but the significance of an adjacent Ets/nuclear factor of activated T cell (NFAT) site has been less clear.

METHODS

Interleukin-5 transcriptional activity was measured by transfection of reporter genes into the human HSB-2 cells and normal T lymphocytes. Expression vectors encoding transcription factors were used for transactivation studies and IL-5 expression measured using reporter genes and mRNA levels. Transcription factor binding was shown with chromatin immunoprecipitation (ChIP).

RESULTS

HSB-2 cells showed high inducible expression of IL-5 mRNA. Mutation of reporter gene plasmids showed the Ets/NFAT site was of equal importance to the AP-1 and GATA-3 sites in regulating IL-5 transcription. Transactivation by Ets1 increased luciferase expression 15-fold, in the absence of stimulation, and AP-1 (c-Fos/c-Jun) and GATA-3 gave transactivations of 85-fold, and 100-fold, respectively. Synergistic interactions were demonstrated between Ets1, GATA-3 and AP-1. Dominant-negative AP-1 inhibited IL-5 transcription. Transactivation by GATA-3 and synergy between GATA-3, Ets1 and AP-1 were verified measuring IL-5 mRNA levels. Chromatin immunoprecipitation showed increased binding of Ets1 and GATA-3 to the IL-5 promoter after stimulation. The importance of the Ets1 site and of synergistic interactions between the three transcription factors were verified with primary human T cells.

CONCLUSION

Ets1, GATA-3 and AP-1 synergize to regulate IL-5 transcription in human T cells.

Clinical significance of a blood eosinophilia in adult T-cell leukemia/lymphoma: a blood eosinophilia is a significant unfavorable prognostic factor

We investigated the clinical significance of a blood eosinophilia in a cohort of 158 consecutive patients with adult T-cell leukemia/lymphoma (ATLL), and multivariate analysis revealed that a blood eosinophilia was an independent and a significant unfavorable prognostic factor. Interestingly, a blood eosinophilia was independent of serum LDH level, which might reflect the tumor burden. The present study shows that measurement of the blood eosinophil count is useful for predicting the prognosis and for determining a suitable treatment strategy for ATLL patients.

Clinical significance of serum Th1-, Th2- and regulatory T cells-associated cytokines in adult T-cell leukemia/lymphoma: high interleukin-5 and -10 levels are significant unfavorable prognostic factors

Patients with adult T-cell leukemia/lymphoma (ATLL) are in a severely immunocompromised state. Therefore, it is assumed that ATLL cells either express particular cytokines or induce their expression in host immune cells, disrupting the balanced production of cytokines and causing the host's immune system to break down. We examined the levels of serum cytokines including T helper type 1- (Th1-) associated cytokines [IFN-gamma, TNF-alpha, and interleukin (IL)-2], Th2-associated cytokines (IL-4, -5 and -6) and regulatory T cell-associated cytokines (IL-10 and TGF-beta1) in 94 ATLL patients, 39 asymptomatic human T-cell lymphotropic virus type-1 (HTLV-1) carriers and 50 healthy adult volunteers, to clarify whether elevated levels of particular cytokines are associated with the prognosis of ATLL patients. On multivariate analysis, high IL-5 and IL-10 levels were independent and significant unfavorable prognostic factors among the ATLL patients. The IL-10 level significantly increased with disease progression at each step from asymptomatic HTLV-1 carrier to ATLL of the indolent variant (chronic and smoldering subtypes) to ATLL of the aggressive variant (acute and lymphoma subtypes). Furthermore, high IL-10 was significantly associated with high lactate dehydrogenase (LDH), indicating that the IL-10 level reflects the tumor burden. The IL-5 level was not associated with disease progression nor LDH. Among ATLL patients with the aggressive variant, high IL-5, but not high IL-10, was an independent and significant unfavorable prognostic factor on multivariate analysis. Measurement of serum IL-5 and IL-10 levels is useful for predicting the prognosis and for determining a suitable treatment strategy for ATLL patients.

A role for Ets1, synergizing with AP-1 and GATA-3 in the regulation of IL-5 transcription in mouse Th2 lymphocytes

IL-5 is a key regulator of eosinophilic inflammation and is selectively expressed by antigen-activated Th2 lymphocytes. An important role for the proximal AP-1 and GATA sites in regulating IL-5 transcription is generally accepted but the significance of an adjacent Ets/NFAT site has remained unclear. We have investigated its role using the mouse Th2 clone D10.G4.1. Transcription of IL-5 reporter gene plasmids could be induced in D10 cells by phorbol myristate acetate/cyclic adenosine monophosphate (PMA/cAMP) stimulation and significantly further enhanced by activation of the mitogen-activated protein (MAP) kinase pathways. Strong induction of IL-5 mRNA was also induced by PMA/cAMP. Mutagenesis showed that the Ets/NFAT site is of critical importance along with the AP-1 and GATA sites in regulating IL-5 transcription stimulated by PMA/cAMP and MAP kinase activation. Transactivation was used to investigate the transcription factors which could function at the three sites and possible synergistic interactions. AP-1 (c-Fos/c-Jun) strongly induced IL-5 transcription and dominant negative AP-1 constructs confirmed that AP-1 plays an important role in regulating IL-5 expression. Ets1, unlike other members of the Ets/NFAT family, synergized strongly with AP-1 suggesting that Ets1 is the family member which functions at the Ets/NFAT site. AP-1/Ets1 transactivation also stimulated IL-5 mRNA expression. Ets1 binding to the proximal promoter region, demonstrated by chromatin immunoprecipitation, was stimulated by PMA/cAMP. The absolute dependence on the binding sites for Ets1, AP-1 and GATA-3 together with the strong synergy between Ets1 and AP-1 suggest close cooperative interactions between the three transcription factors in the regulation of IL-5 expression in mouse T cells.

The conserved lymphokine element 0 is a powerful activator and target for corticosteroid inhibition in human interleukin-5 transcription

The role of eosinophilia in allergic disorders indicates hIL-5 as a potential target for therapy. The conservation of hIL-5 gene proximal elements suggests they are important in controlling expression. Corticosteroids are important in the treatment of allergy, and are powerful inhibitors of IL-5 expression. This study aimed at understanding the role of hIL-5 conserved proximal elements, and elucidating the target of corticosteroid activity, in hIL-5 gene expression. Methods used include transient transfection of PBMC and PER117 cells with hIL-5 deletion constructs, EMSA, Western Blotting, and RT-PCR. The conserved proximal CLE0/TATA elements driving a reporter gene gave similar or higher expression than a 500 bp promoter in primary human T cells and a T-cell line. Two and three copies of IL-5 CLE0 upstream of the silent IL-4 minimal promoter gave 30-45 fold increases in expression in forward orientation, but little activity in reverse orientation. Consequently, CLE0 is a powerful activator but not a classical enhancer. Deletion analysis identified CLE0 as the key element in the inhibition of IL-5 reporter constructs by dexamethasone, and RT-PCR analysis indicated that GILZ expression correlated with dexamethasone-induced inhibition of IL-5. Ectopic expression of GILZ, confirmed by western blotting, gave a 90% inhibition of promoter constructs in absence of dexamethasone. CLE0 is a powerful activator sufficient for the inducible expression of IL-5, and functions when moved upstream in a heterologous promoter. CLE0 is also the main target for IL-5 inhibition by dexamethasone, and we present evidence consistent with a role of GILZ in this.

IL-2- and STAT5-regulated cytokine gene expression in cells expressing the Tax protein of HTLV-1

Interleukin-2 (IL-2) mediates cell cycle progression and antiapoptosis in human T cells via several signal transduction pathways. The Tax protein of the human T-cell leukemia virus type I (HTLV-1) deregulates cell growth and alters the role of IL-2 in infected cells. However, Tax-immortalized cells stay dependent on IL-2, suggesting that events besides HTLV-1 gene expression are required for leukemia to develop. Here, IL-2-dependent and -independent events were analysed in a human T cell line immortalized by Tax. These studies show that, of the signaling pathways evaluated, only STAT5 remains dependent. Microarray analyses revealed several genes, including il-5, il-9 and il-13, are uniquely upregulated by IL-2 in the presence of Tax. Bioinformatics and supporting molecular biology show that some of these genes are STAT5 targets, explaining their IL-2 upregulation. These results suggest that IL-2 and viral proteins work together to induce gene expression, promoting the hypothesis that deregulation via the constitutive activation of STAT5 may lead to the IL-2-independent phenotype of HTLV-1-transformed cells.

Role of GATA-3 in IL-5 gene transcription by CD4+ T cells of asthmatic patients

BACKGROUND

Helper T cells and T cell cytokines play central roles in allergic disorders including bronchial asthma. We reported enhanced IL-5 production by peripheral blood T cells of asthmatic patients. A transcription factor, GATA-3, has been implicated in IL-5 gene expression. This study was undertaken to clarify the role of GATA-3 in the upregulation of IL-5 synthesis in asthmatic patients.

METHOD

Peripheral CD4+ T cells were transfected with an IL-5 promoter reporter construct as well as its mutants in the presence or absence of a GATA-3 expression vector. Messenger RNA expression level of GATA-3 in CD4+ T cells of asthmatic subjects was compared to that of healthy donors.

RESULTS

IL-5 promoter activity in CD4+ T cells was enhanced by overexpression of GATA-3, whereas it was diminished by the introduction of mutations in the putative GATA-3 binding sites. The GATA-3 expression level in CD4+ T cells of asthmatic patients was equivalent to that of healthy controls.

CONCLUSION

The expression level of GATA-3 may not be an essential factor to cause IL-5 hyperproduction in bronchial asthma, though GATA-3 is crucially involved in IL-5 gene transcription in human peripheral CD4+ T cells.

HTLV-1 HBZ suppresses AP-1 activity by impairing both the DNA-binding ability and the stability of c-Jun protein

Disruption of transcriptional control of cellular genes by human T-cell leukemia virus type-1 (HTLV-1) is thought to be associated, at least in part, with the development of adult T-cell leukemia. It has been reported that activating protein-1 (AP-1) is dysregulated by HTLV-1 infection. HTLV-1-encoded Tax elevates AP-1 activity through the induction of AP-1 family member gene expression, including c-Jun, JunD, c-Fos, and Fra-1. However, the precise mechanism by which HTLV-1 regulates AP-1 activity remains to be addressed. Recently, a novel viral protein named HTLV-1 basic leucine-zipper factor, HBZ, has been shown to interact with c-Jun and repress c-Jun-mediated transcription by abrogating its DNA-binding activity. In the course of investigating HBZ function, we found that HBZ reduced the steady-state levels of c-Jun, and the levels were restored by treatment with a proteasome inhibitor. Together, this indicates that HBZ promotes c-Jun degradation through a proteasome-dependent pathway. Furthermore, HBZ deletion mutants revealed that both the N-terminal and leucine-zipper region of HBZ were required for the elimination of c-Jun. These results suggest dual effects of HBZ on the suppression of AP-1 activity by inhibiting c-Jun function, which may contribute to the dysregulation of cell proliferation.

Tax protein of human T-cell leukaemia virus type 1 induces interleukin 17 gene expression in T cells

Tax protein of human T-cell leukaemia virus type 1 (HTLV-1) induces the expression of several cellular genes that are involved in T cell activation and proliferation. In this study, it was observed that Tax upregulated the expression of human interleukin 17 (IL17), a cytokine mainly produced by activated CD4(+) memory T cells. Indeed, IL17 mRNA was highly expressed in HTLV-1-infected T cells as well as in Tax-expressing Jurkat T cells, whereas it was not detectable in HTLV-1-negative T cell lines. The clinical relevance of these observations was further demonstrated by quantitative assessment of IL17 expression in lymphocytes isolated from one HTLV-1-infected patient. To define the transcriptional activation of the IL17 gene by Tax, the 5'-flanking region of this gene was cloned and a reporter gene analysis performed. The presence of a Tax-responsive region spanning 614 bp upstream of the initiation start site was identified, in HeLa as well as in Jurkat cells, stimulated with phorbol myristate acetate and Ca(2+) ionophore. Finally, Tax mutants were used to show that the transcriptional activation of the IL17 promoter by Tax was dependent on the CREB/ATF pathway. As IL17 upregulates the expression of several pro-inflammatory cytokines, these observations provide new insights into the involvement of the Tax protein in the pathophysiology of HTLV-1-associated inflammatory disorders.

The HBZ factor of human T-cell leukemia virus type I dimerizes with transcription factors JunB and c-Jun and modulates their transcriptional activity

The human T-cell leukemia virus type I (HTLV-I)-encoded Tax protein activates transcription from the viral promoter via association with the cellular basic leucine zipper factor cAMP-response element-binding protein-2. Tax is also able to induce cellular transformation of T lymphocytes probably by modulating transcriptional activity of cellular factors, including nuclear factor-kappaB, E2F, activator protein-1 (AP-1), and p53. Recently, we characterized in HTLV-I-infected cells the presence of a novel viral protein, HBZ, encoded by the complementary strand of the HTLV-I RNA genome (Gaudray, G., Gachon, F., Basbous, J., Biard-Piechaczyk, M., Devaux, C., and Mesnard, J.-M. (2002) J. Virol. 76, 12813-12822). HBZ is a nuclear basic leucine zipper protein that down-regulates Tax-dependent viral transcription by inhibiting the binding of cAMP-response element-binding protein-2 to the HTLV-I promoter. In searching for other cellular targets of HBZ, we identified two members of the Jun family, JunB and c-Jun. Co-immunoprecipitation and cellular colocalization confirmed that HBZ interacts in vivo with JunB and c-Jun. When transiently introduced into CEM cells with a reporter gene containing the AP-1 site from the collagenase promoter, HBZ suppressed transactivation by c-Jun. On the other hand, the combination of HBZ with Jun-B had higher transcriptional activity than JunB alone. Consistent with the structure of its basic domain, we demonstrate that HBZ decreases the DNA-binding activity of c-Jun and JunB. Last, we show that c-Jun is no longer capable of activating the basal expression of the HTLV-I promoter in the presence of HBZ in vivo. Our results support the hypothesis that HBZ could be a negative modulator of the Tax effect by controlling Tax expression at the transcriptional level and by attenuating activation of AP-1 by Tax.

Cell context-dependent differences in the induction of E2F-1 gene expression by 17 beta-estradiol in MCF-7 and ZR-75 cells

17 beta-Estradiol (E2) induces E2F-1 gene expression in ZR-75 and MCF-7 human breast cancer cells. Analysis of the E2F-1 gene promoter in MCF-7 cells previously showed that hormone-induced transactivation required interactions between estrogen receptor alpha (ER alpha)/Sp1 bound to upstream GC-rich sites and NFYA bound to downstream CCAAT sites within the -169 to -54 region of the promoter. This same region of the E2F-1 promoter was also E2 responsive in ER alpha-positive ZR-75 cells; however, further analysis of the promoter showed that cooperative ER alpha/Sp1/NFY interactions were not necessary for hormone-induced transactivation in ZR-75 cells. The upstream GC-rich motifs (-169 to -111) are activated independently by ER alpha/Sp1 in ZR-75 but not MCF-7 cells, and a construct (pE2F-1j(m1)) containing the -122 to -54 downstream CCAAT site that bound NFYA was also E2 responsive. E2 also induced reporter gene activity in ZR-75 cells transfected with an expression plasmid for a chimeric protein containing the DNA-binding domain of the yeast GAL4 protein fused to NFYA (pM-NFYA) and a construct containing five tandem GAL4 response elements. Subsequent studies showed that hormonal activation of pE2F-1j(m1) and pM-NFYA are dependent on nongenomic pathways in which E2 activates cAMP/protein kinase A. Hormone-dependent regulation of E2F-1 gene expression in ZR-75 and MCF-7 involves the same cis elements and interacting transcription factors but different mechanisms, demonstrating the importance of cell context on transactivation pathways, even among ER-positive breast cancer cell lines.

Transcriptional regulation of the IL-5 gene in peripheral T cells of asthmatic patients

Mechanisms that underlie the regulation of IL-5 gene expression in human peripheral T cells remain incompletely defined because of the low efficiency of transfection of plasmid constructs into non-transformed T cells. To elucidate the cellular and molecular mechanisms of IL-5 production, concanavalin A (ConA)-stimulated blastocytes derived from peripheral blood lymphocytes of asthmatic patients were employed in this study. Transcriptional activity of the synthetic human IL-5 promoter in ConA-stimulated blastocytes correlated with the production of IL-5. Deletion analysis of the reporter gene showed that the cis-regulatory element located at - 119 to - 80 is critical for inducible IL-5 promoter activity. Electrophoretic mobility shift assay revealed that an oligonucleotide probe corresponding to the element (- 119 to - 90) gave two specific bands. The slower migrating band was absolutely dependent on stimulation and was composed of a co-operative complex of the transcription factors, nuclear factor of activated T cells (NFAT) and activating protein-1 (AP-1). The faster migrating band was also inducible and was identified as AP-1-less NFAT. Mutation of either the NFAT or AP-1 element abrogated the slower migrating band and at the same time abolished transcriptional activity of the human IL-5 promoter/enhancer gene. Cyclosporin A equivalently suppressed DNA-binding activity of the composite NFAT/AP-1 site, promoter activity and protein production of IL-5. In conclusion, these data suggests that the composite NFAT/AP-1 binding element (- 115 to - 100) plays a crucial role in IL-5 synthesis by peripheral T cells of asthmatic patients.

Identification of a candidate regulatory region in the human CD8 gene complex by colocalization of DNase I hypersensitive sites and matrix attachment regions which bind SATB1 and GATA-3

To locate elements regulating the human CD8 gene complex, we mapped nuclear matrix attachment regions (MARs) and DNase I hypersensitive (HS) sites over a 100-kb region that included the CD8B gene, the intergenic region, and the CD8A gene. MARs facilitate long-range chromatin remodeling required for enhancer activity and have been found closely linked to several lymphoid enhancers. Within the human CD8 gene complex, we identified six DNase HS clusters, four strong MARs, and several weaker MARs. Three of the strong MARs were closely linked to two tissue-specific DNase HS clusters (III and IV) at the 3' end of the CD8B gene. To further establish the importance of this region, we obtained 19 kb of sequence and screened for potential binding sites for the MAR-binding protein, SATB1, and for GATA-3, both of which are critical for T cell development. By gel shift analysis we identified two strong SATB1 binding sites, located 4.5 kb apart, in strong MARs. We also detected strong GATA-3 binding to an oligonucleotide containing two GATA-3 motifs located at an HS site in cluster IV. This clustering of DNase HS sites and MARs capable of binding SATB1 and GATA-3 at the 3' end of the CD8B gene suggests that this region is an epigenetic regulator of CD8 expression.

Human T-cell lymphotropic virus type I Tax activates lung resistance-related protein expression in leukemic clones established from an adult T-cell leukemia patient

OBJECTIVE

We examined the significance of human T-cell lymphotropic virus type I (HTLV-I) Tax protein-induced resistance to anticancer drugs and the relationship between Tax and multidrug resistance proteins.

MATERIALS AND METHODS

S1T cell, a leukemic non-Tax-producing T-cell clone established from an adult T-cell leukemia (ATL) patient, S1TcTax05 and S1TcTax10 clones, transfected with Tax stably expressing cDNA, and S1Tneo, transfected with a neomycin-resistant gene, were examined for Tax-related anticancer drug resistance. Resistance of those cells to the anticancer drugs doxorubicin, etoposide, cisplatin, and vindesine was tested with the MTT method. Expression of multidrug resistance protein mRNAs (MDR1, MRP1, cMOAT/MRP2, and LRP) was analyzed with reverse transcriptase polymerase chain reaction (RT-PCR). Doxorubicin subcellular distribution in those cells was examined by fluorescence microscopy.

RESULTS

S1TcTax05 and S1TcTax10 showed resistance to doxorubicin, etoposide, and vindesine, but not to cisplatin as compared with S1T or S1Tneo. RT-PCR demonstrated that MRP1 mRNA was expressed, but MDR1, cMOAT, and LRP mRNAs were not in S1T or S1Tneo. Marked expression of LRP mRNA was detected, but no change of MDR1, MRP1, or cMOAT mRNA expression in Tax-expressing S1TcTax05 and S1TcTax10. Fluorescence microscopy demonstrated that doxorubicin was distributed mainly in the cytoplasm of S1TcTax05 and S1TcTax10, and in the nucleus of S1T and S1Tneo.

CONCLUSIONS

These findings suggest that Tax-related drug resistance of ATL cells is due to LRP and not MDR1, as reported previously. These findings in cells derived from an ATL patient suggest a novel mechanism for drug resistance in Tax-expressing ATL cells.

Roles of CCAAT/enhancer-binding protein in transcriptional regulation of the human IL-5 gene

Interleukin-5 (IL-5) plays a critical role in the pathogenesis of eosinophil-associated allergic disorders, such as asthma. IL-5 may also play a major role in the development of eosinophilia-associated lymphoproliferative disorders caused by human T lymphotropic virus type I (HTLV-I). In this study, we have investigated the control mechanisms for IL-5 production and found that ectopic expression of NF-IL6 (C/EBPbeta) increases endogenous IL-5 mRNA expression. The IL-5 promoter contains four C/EBP consensus sequences. We show here that one of the C/EBP site at - 235 promoter region binds to NF-IL6 protein with high affinity and interacts with NF-IL6 and NF-IL6beta (C/EBPdelta) in Jurkat T cells. Mutations within the C/EBP sequence reduced the promoter activity in response to T cell activation by more than 50 %. In addition, we show that in vivo inducible expression of Tax protein in Jurkat T cells stably transfected with Tax further increased ionomycin plus phorbol ester stimulated IL-5 promoter activity. The effect of Tax on IL-5 promoter activity was abolished when the C/EBP site was mutated. Thus, the C/EBP site may be also involved in HTLV-I Tax-mediated up-regulation of IL-5 gene expression. Our data suggest that C/EBP proteins may regulate IL-5 gene expression in response to different stimulation signals.

Human T cell leukemia virus type I Tax enhances IL-4 gene expression in T cells

The human T cell leukemia virus type-1 (HTLV-1) is the etiologic agent of adult T cell leukemia (ATL). Since the HTLV-I-encoded transactivator Tax has been shown to activate many cellular genes including cytokine genes interleukin (IL-)1alpha, 2, 5, 6, 8, 10 and 15, we ask whether Tax also affects IL-4 expression. In this study, we show that addition of recombinant Tax proteins greatly enhances IL-4 secretion in human peripheral primary T cells. Transient transfection studies showed that ectopic expression of Tax significantly enhanced IL-4 promoter activity. The IL-4 promoter contains a strong NF-IL6 (PRE-I element) and a NF-AT/NF-kappaB overlapping site (P1 element). We show that expression of Tax stimulates NF-IL6 binding to the PRE-I element and, consequently, enhances PRE-I-mediated transcriptional activity. Using Jurkat T cell lines which stably express Tax fused to the hormone binding domain of the human estrogen receptor (ER), we show that Tax enhances endogenous IL-4 mRNA expression and increases IL-4 promoter activity in a hormone-dependent manner. Mutation analysis revealed that the IL-4 PRE-I (NF-IL6 site) and the P1 (NF-AT/NF-kappaB site) are involved in Tax-mediated transactivation. Our studies provide the first evidence of the functional involvement of Tax in IL-4 gene regulation.

Expression of GATA family of transcription factors in T-cells, monocytes and bronchial biopsies

GATA-binding proteins are a subfamily of zinc finger transcription factors with six members (GATA-1-6) that interact with the GATA deoxyribonucleic acid (DNA) sequence. This sequence is found in the regulatory regions of many genes including those encoding T-helper 2 (Th2)-like cytokines, receptors, adhesion molecules and enzymes, which may be important in the pathogenesis of bronchial asthma. The expression of GATA-3, 4 and -6 was investigated in peripheral blood T-lymphocytes and monocytes and bronchial biopsies from 11 normal subjects and 10 steroid-naive asthmatic patients. Using Western blot analysis, T-cells from asthmatic subjects expressed 5 times the level of GATA-3 compared to that in normals. Confocal microscopy indicated that GATA-3 expression was both nuclear and cytoplasmic. GATA DNA binding complex containing GATA-3 was elevated in Th2 cells as determined by electrophorectic mobility shift assay. In contrast, monocytes from normal and asthmatic subjects expressed GATA-4 and -6 in equal amounts, but no GATA-3 was found. Using immunohistochemistry in bronchial biopsies, epithelial cells expressed high levels of GATA-3, GATA-4 and GATA-6 proteins. Comparison of Western blots of bronchial biopsies showed no significant differences between normal and asthmatic subjects. In conclusion, the increased expression of GATA-3 in asthmatic T-cells may underlie augmented T-helper 2-like cytokines in this disease. However, the unaltered GATA-3 expression in epithelial cells suggests a distinct role for GATA-3 in these cells unrelated to T-helper 2-like cytokine release. Finally, no evidence was found for an increased expression of GATA-4 and GATA-6 in asthma.

Molecular pathways in virus-induced cytokine production

Virus infections induce a proinflammatory response including expression of cytokines and chemokines. The subsequent leukocyte recruitment and antiviral effector functions contribute to the first line of defense against viruses. The molecular virus-cell interactions initiating these events have been studied intensively, and it appears that viral surface glycoproteins, double-stranded RNA, and intracellular viral proteins all have the capacity to activate signal transduction pathways leading to the expression of cytokines and chemokines. The signaling pathways activated by viral infections include the major proinflammatory pathways, with the transcription factor NF-kappaB having received special attention. These transcription factors in turn promote the expression of specific inducible host proteins and participate in the expression of some viral genes. Here we review the current knowledge of virus-induced signal transduction by seven human pathogenic viruses and the most widely used experimental models for viral infections. The molecular mechanisms of virus-induced expression of cytokines and chemokines is also analyzed.

Transcriptional activation of deoxyribonucleic acid polymerase alpha gene expression in MCF-7 cells by 17 beta-estradiol

Treatment of MCF-7 human breast cancer cells with 17beta-estradiol (E(2)) results in increased DNA synthesis and cell proliferation and enhanced enzyme activities associated with purine/pyrimidine biosynthesis. The mechanism of enhanced DNA polymerase alpha activity was investigated by analysis of the promoter region of this gene. E(2) induced luciferase (reporter gene) activity in MCF-7 cells transfected with pDNAP1, pDNAP2, and pDNAP3 containing -1515 to +45, -248 to +45 and -116 to +45 inserts from the DNA polymerase alpha gene promoter, whereas no induction was observed with pDNAP4 (-65 to +45 insert). The induction response was dependent on cotransfection with estrogen receptor alpha (ER(alpha)), and transactivation was also observed with a mutant ER(alpha) that did not express the DNA-binding domain. Subsequent functional, DNA binding, and DNA footprinting studies showed that a GC-rich region at -106 to -100 was required for E(2)-mediated transactivation, and Sp1 protein, but not ER(alpha), bound this sequence. Transcriptional activation of DNA polymerase alpha by E(2) is associated with ER(alpha)/Sp1 action at a proximal GC-rich promoter sequence, and this gene is among a growing list of E(2)-responsive genes that are induced via ER(alpha)/Sp1 protein interactions that do not require direct binding of the hormone receptor to DNA.

A unique mRNA initiated within a middle intron of WHSC1/MMSET encodes a DNA binding protein that suppresses human IL-5 transcription

Human interleukin (IL)-5 gene transcription is regulated by several transcription factor binding sites, including CLE 0, GATA, and a region from position -123 to -92 known as response element (RE)-II. By expression cloning, a partial protein was identified that bound to concatamers of RE-II. Recombinant protein derived from this initial complementary DNA (cDNA) encoding the partial protein specifically bound to RE-II-containing oligonucleotides in electromobility shift assays. The complete sequence (3,649 bp) was determined by 5' rapid amplification of cDNA ends and comparisons to existing ESTs, and found to be identical to the 3' half of Wolf-Hirschhorn syndrome candidate 1, (WHSC1; also known as Multiple Myeloma SET domain [MMSET]). The full-length protein contains an SET domain and two plant homeodomain-type zinc fingers. Transcription initiation of RE-II binding protein (RE-IIBP) messenger RNA (mRNA) uniquely occurred within the middle of WHSC1 near a region that exhibits complex mRNA splicing. RE-IIBP reactive polyclonal antisera identified proteins in human T-cell nuclear protein extracts of 62 and 66 kD that were consistent with the length of the longest open reading frame in RE-IIBP. In contrast, WHSC1 is predicted to encode a protein of 136 kD. In activated human Jurkat and murine D10.G4.1 T cells, expression of full-length and truncated forms of RE-IIBP repressed RE-II promoter activity of a 5X-RE-II luciferase reporter construct by as much as 75%. In addition, RE-IIBP expressed in activated D10.G4.1 T cells inhibited endogenous murine IL-5 production. The repressor activity of RE-IIBP is consistent with the presence of an SET domain that is found in other proteins that act as gene silencers.

Acetylation of GATA-3 affects T-cell survival and homing to secondary lymphoid organs

Acetylation of a transcription factor has recently been shown to play a significant role in gene regulation. Here we show that GATA-3 is acetylated in T cells and that a mutation introduced into amino acids 305-307 (KRR-GATA3) creates local hypoacetylation in GATA-3. Remarkably, KRR-GATA3 possesses the most potent suppressive effect when compared with other mutants that are disrupted in putative acetylation targets. Expressing this mutant in peripheral T cells results in defective T-cell homing to systemic lymphnodes, and prolonged T-cell survival after activation. These findings have significant implications in that the acetylation state of GATA-3 affects its physiological function in the immune system and, more importantly, provides evidence for the novel role of GATA-3 in T-cell survival and homing to secondary lymphoid organs.

Inhibition of vascular endothelial growth factor expression in HEC1A endometrial cancer cells through interactions of estrogen receptor alpha and Sp3 proteins

Treatment of HEC1A endometrial cancer cells with 10 nm 17beta-estradiol (E2) resulted in decreased vascular endothelial growth factor (VEGF) mRNA expression, and a similar response was observed using a construct, pVEGF1, containing a VEGF gene promoter insert from -2018 to +50. In HEC1A cells transiently transfected with pVEGF1 and a series of deletion plasmids, it was shown that E2-dependent down-regulation was dependent on wild-type estrogen receptor alpha (ERalpha) and reversed by the anti-estrogen ICI 182, 780, and this response was not affected by progestins. Deletion analysis of the VEGF gene promoter identified an overlapping G/GC-rich site between -66 to -47 that was required for decreased transactivation by E2. Protein-DNA binding studies using electrophoretic mobility shift and DNA footprinting assays showed that both Sp1 and Sp3 proteins bound this region of the VEGF promoter. Coimmunoprecipitation and pull-down assays demonstrated that Sp3 and ERalpha proteins physically interact, and the interacting domains of both proteins are different from those previously observed for interactions between Sp1 and ERalpha proteins. Using a dominant negative form of Sp3 and transcriptional activation assays in Schneider SL-2 insect cells, it was confirmed that ERalpha-Sp3 interactions define a pathway for E2-mediated inhibition of gene expression, and this represents a new mechanism for decreased gene expression by E2.

Molecular interactions involved in the transactivation of the human T-cell leukemia virus type 1 promoter mediated by Tax and CREB-2 (ATF-4)

The human T-cell leukemia virus type 1 (HTLV-1) Tax protein activates viral transcription through three 21-bp repeats located in the U3 region of the HTLV-1 long terminal repeat and called Tax-responsive elements (TxREs). Each TxRE contains nucleotide sequences corresponding to imperfect cyclic AMP response elements (CRE). In this study, we demonstrate that the bZIP transcriptional factor CREB-2 is able to bind in vitro to the TxREs and that CREB-2 binding to each of the 21-bp motifs is enhanced by Tax. We also demonstrate that Tax can weakly interact with CREB-2 bound to a cellular palindromic CRE motif such as that found in the somatostatin promoter. Mutagenesis of Tax and CREB-2 demonstrates that both N- and C-terminal domains of Tax and the C-terminal region of CREB-2 are required for direct interaction between the two proteins. In addition, the Tax mutant M47, defective for HTLV-1 activation, is unable to form in vitro a ternary complex with CREB-2 and TxRE. In agreement with recent results suggesting that Tax can recruit the coactivator CREB-binding protein (CBP) on the HTLV-1 promoter, we provide evidence that Tax, CREB-2, and CBP are capable of cooperating to stimulate viral transcription. Taken together, our data highlight the major role played by CREB-2 in Tax-mediated transactivation.

p300 and p300/cAMP-responsive element-binding protein associated factor interact with human T-cell lymphotropic virus type-1 Tax in a multi-histone acetyltransferase/activator-enhancer complex

The human T-cell lymphotropic virus, type (HTLV)-1 trans-activator, Tax, coordinates with cAMP-responsive element-binding protein (CREB) and the transcriptional co-activators p300/CBP on three 21-base pair repeat elements in the proviral long terminal repeat (LTR) to promote viral mRNA transcription. Recruitment of p300/CBP to the activator-enhancer complex, however, is insufficient to support Tax-dependent LTR trans-activation. Here, we report that the p300/CBP-associated factor (P/CAF) is a critical and integral component of the functional HTLV-1 activator-enhancer complex. The HTLV-1 Tax protein directly binds P/CAF in vitro and co-immunoprecipitates with this co-activator in vivo. The Tax mutants (K88A and V89A) defective for p300/CBP-binding and LTR trans-activation, retained their abilities to interact with P/CAF. The M47 mutant (L319R, L320S) protein, which has previously been shown to interact with p300/CBP, by contrast, failed to form complexes with P/CAF and is impaired in LTR trans-activation. Furthermore, LTR trans-activation by Tax is competitively inhibited by the adenoviral E1A 12S gene product, which displaces P/CAF from p300/CBP and inhibits the histone acetyltransferase activities of both P/CAF and p300/CBP. This inhibition is partially reversed by exogenously added P/CAF. These results imply that simultaneous recruitment of two distinct co-activators (p300/CBP and P/CAF) by Tax is essential for the assembly of a trans-activation competent, nucleoprotein complex.

Mechanisms of transcriptional activation of bcl-2 gene expression by 17beta-estradiol in breast cancer cells

bcl-2 gene expression is induced by 17beta-estradiol (E2) in T47D and MCF-7 human breast cancer cells, and the mechanism of E2 responsiveness was further investigated by analysis of the bcl-2 gene promoter. The -1602 to -1534 distal region (bcl-2j) of the promoter was E2-responsive; however, in gel mobility shift assays, the estrogen receptor alpha (ER(alpha)) did not bind [(32)P]bcl-2j, whereas Sp1 protein formed a retarded band complex. Further analysis demonstrated that the upstream region (-1603 to -1579) of the bcl-2 gene promoter contained two GC/GA-rich sites at -1601 (5'-GGGCTGG-3') and -1588 (3'-GGAGGG-5') that bound Sp1 protein. Subsequent studies confirmed that transactivation by E2 was dependent on ER(alpha)/Sp1 interactions with both GC-rich sites, and this was confirmed by in vitro footprinting. In contrast, a 21-base pair E2-responsive downstream region (-1578 to -1534) did not bind Sp1 or ER(alpha) protein; however, analysis of a complex binding pattern with nuclear extracts showed that ATF-1 and CREB-1 bound to this motif. These data coupled with results of transient transfection studies demonstrated that transcriptional activation by E2 of the -1578 to -1534 region of the bcl-2 gene promoter was dependent on induction of cAMP and subsequent activation through a cAMP response element. Thus, hormone regulation of bcl-2 gene expression in breast cancer cells involves multiple enhancer elements and E2-mediated transactivation does not require direct binding of the estrogen receptor with promoter DNA.

Regulation of metallothionein gene transcription. Identification of upstream regulatory elements and transcription factors responsible for cell-specific expression of the metallothionein genes from Caenorhabditis elegans

Metallothioneins are small, cysteine-rich proteins that function in metal detoxification and homeostasis. Metallothionein transcription is controlled by cell-specific factors, as well as developmentally modulated and metal-responsive pathways. By using the nematode Caenorhabditis elegans as a model system, the mechanism that controls cell-specific metallothionein transcription in vivo was investigated. The inducible expression of the C. elegans metallothionein genes, mtl-1 and mtl-2, occurs exclusively in intestinal cells. Sequence comparisons of these genes with other C. elegans intestinal cell-specific genes identified multiple repeats of GATA transcription factor-binding sites (i.e. GATA elements). In vivo deletion and site-directed mutation analyses confirm that one GATA element in mtl-1 and two in mtl-2 are required for transcription. Electrophoretic mobility shift assays show that the C. elegans GATA transcription factor ELT-2 specifically binds to these elements. Ectopic expression of ELT-2 in non-intestinal cells of C. elegans activates mtl-2 transcription in these cells. Likewise, mtl-2 is not expressed in nematodes in which elt-2 has been disrupted. These results indicate that cell-specific transcription of the C. elegans metallothionein genes is regulated by the binding of ELT-2 to GATA elements in these promoters. Furthermore, a model is proposed where ELT-2 constitutively activates metallothionein expression; however, a second metal-responsive factor prevents transcription in the absence of metals.

Pathological roles of interleukin-15 in adult T-cell leukemia

Interleukin-15 (IL-15) is a 14-kDa glycoprotein belonging to the same four helix bundle-cytokine family as IL-2. Although the biological activity of IL-15 in vitro has been studied extensively, its physiological role is still obscure. The receptors for IL-15 and IL-2 consist of three subunits, an unique alpha chain and shared beta and gamma chains. Since beta and gamma chains transduce the signals from the receptors, both cytokines share similar biologic functions, although IL-15 and IL-2 do not have sequence homology. The alpha chains function to increase binding affinity for each cytokines. Adult T-cell leukemia (ATL) cells constitutively express the IL-2 receptor (IL-2R) alpha and expression is believed to be essential in the early stages of disease development. We have recently shown that ATL cells also express the complete form of IL-15R including the alpha chain, and that ATL cells proliferate in response to exogenous IL-15. Since the mRNA of IL-15 is ubiquitous and is detected in many tissues and cells, it is possible that IL-15R stimulation is involved in the development and progression of ATL. Here, we review recent studies on IL-15 and IL-15R and their association with ATL and other lymphoproliferative disorders.

The transcription factor c-Maf controls the production of interleukin-4 but not other Th2 cytokines

IL-4 promotes the differentiation of naive CD4+ T cells into IL-4-producing T helper 2 (Th2) cells. Previous work provided suggestive but not conclusive evidence that the transcription factor c-Maf directed the tissue-specific expression of IL-4. It was not known whether c-Maf controlled the transcription of other Th2 cytokine genes. To elucidate the role of c-Maf in vivo, we examined cytokine production in mice lacking c-Maf (c-maf(-/-)). CD4+ T cells and NK T cells from c-maf(-/-) mice were markedly deficient in IL-4 production. However, the mice produced normal levels of IL-13 and IgE, and, when differentiated in the presence of exogenous IL-4, c-maf(-/-) T cells produced approximately normal levels of other Th2 cytokines. We conclude that c-Maf has a critical and selective function in IL-4 gene transcription in vivo.

Regulation of the human interleukin-5 promoter by Ets transcription factors. Ets1 and Ets2, but not Elf-1, cooperate with GATA3 and HTLV-I Tax1

Interleukin-5 (IL-5), expressed primarily by type-2 T helper (Th2) cells, plays an important role in the development of allergic diseases, such as allergic asthma. Studying the regulation of IL-5 gene expression by Ets transcription factors, we found that Ets1 and Ets2, but not Elf-1, were able to activate the human IL-5 promoter in Jurkat T-cells. This required the presence of either phorbol 12-myristate acetate (PMA) plus ionomycin or PMA plus the viral protein HTLV-I Tax1. By mutation studies, it could be shown that Ets1 and Ets2 exerted their effects on the IL-5 promoter through a GGAA motif within the Cle0 element. In myeloid Kasumi cells, Ets1 and Ets2 failed to stimulate IL-5 promoter activity, unless the T-cell specific transcription factor GATA3 was added. These results show, for the first time, that Ets1 and Ets2 are able to cooperate with GATA3. Both ionomycin and Tax1 increased the combined effect of GATA3 with Ets1 and Ets2 in the presence of PMA. The data further demonstrate that, in addition to Ets1, Ets2 is also able to functionally cooperate with Tax1. The synergism of GATA3 with either Ets1 or Ets2 may play an important role in calcium- or Tax1-dependent regulation of IL-5 expression in Th2 cells or in HTLV-I transformed adult T-cell leukemia cells, respectively.

Characterisation of inducible DNase I hypersensitive sites flanking the human interleukin-5 gene

Interleukin-5 (IL-5) production is necessary for eosinophilia associated with allergic conditions and parasitic infection. IL-5 mRNA is transiently expressed by activated T-lymphocytes. In this report, we have analysed DNA regulatory regions associated with inducible IL-5 expression in the human HSB-2 T-cell line. Only low levels of transcriptional activity were induced in cells transfected with up to 1.2 kb of DNA upstream of the IL-5 gene. DNase I hypersensitivity analysis was employed to identify additional regulatory sequences located outside this region. Two hypersensitivity sites (HS) were identified, one 2.5 kb 5' and the other 1.6 kb 3' from the gene, that were induced on activation of HSB-2 cells by stimuli that induced IL-5 expression. The 5' site, but not the 3' site, was found in primary human T-cells. The presence of the 5' HS did not always coincide with IL-5 expression. Inclusion of the region encompassing the 5' HS in promoter studies mediated a moderate increase in transcriptional activity, suggesting that enhancer elements essential for induction of maximal IL-5 transcription reside at a greater distance from the IL-5 gene.

Eosinophilia associated with adult T-cell leukemia: role of interleukin 5 and granulocyte-macrophage colony-stimulating factor

To clarify the mechanism of eosinophilia in adult T-cell leukemia (ATL), we studied three ATL patients having marked eosinophilia. Eosinophil-predominant colony-stimulating activity was detected in the serum of one patient and in the conditioned media (CM) from cultured ATL cells from two patients. Soluble interleukin 5 (IL-5), but no interleukin 3 (IL-3) and granulocyte-macrophage colony-stimulating factor (GM-CSF), was detected in sera from all patients. On the other hand, GM-CSF was produced in vitro by ATL cells from all cases, whereas detectable IL-3 and IL-5 was produced by cells from only one, suggesting that in the other two cases, the serum IL-5 was produced by the normal reacting lymphocytes. The fact that no patient showed marked neutrophilia supports the possibility that IL-5 may have a leading role in the development of eosinophilia, with GM-CSF produced by ATL cells playing a complementary role.