AP-1 Transcription Factor Binding Research Articles

Comparative genomics analyses reveal sequence determinants underlying interspecies variations in injury-responsive enhancers

BackgroundInjury induces profound transcriptional remodeling events, which could lead to only wound healing, partial tissue repair, or perfect regeneration in different species. Injury-responsive enhancers (IREs) are cis-regulatory elements activated in response to injury signals, and have been demonstrated to promote tissue regeneration in some organisms such as zebrafish and flies. However, the functional significances of IREs in mammals remain elusive. Moreover, whether the transcriptional responses elicited by IREs upon injury are conserved or specialized in different species, and what sequence features may underlie the functional variations of IREs have not been elucidated.ResultsWe identified a set of IREs that are activated in both regenerative and non-regenerative neonatal mouse hearts upon myocardial ischemia-induced damage by integrative epigenomic and transcriptomic analyses. Motif enrichment analysis showed that AP-1 and ETS transcription factor binding motifs are significantly enriched in both zebrafish and mouse IREs. However, the IRE-associated genes vary considerably between the two species. We further found that the IRE-related sequences in zebrafish and mice diverge greatly, with the loss of IRE inducibility accompanied by a reduction in AP-1 and ETS motif frequencies. The functional turnover of IREs between zebrafish and mice is correlated with changes in transcriptional responses of the IRE-associated genes upon injury. Using mouse cardiomyocytes as a model, we demonstrated that the reduction in AP-1 or ETS motif frequency attenuates the activation of IREs in response to hypoxia-induced damage.ConclusionsBy performing comparative genomics analyses on IREs, we demonstrated that inter-species variations in AP-1 and ETS motifs may play an important role in defining the functions of enhancers during injury response. Our findings provide important insights for understanding the molecular mechanisms of transcriptional remodeling in response to injury across species.

112-OR: Integrative Analysis of Chromatin Accessibility and Genetic Risk in T1D Patients and Controls

Motivation: Twin studies estimate 50% of type 1 diabetes (T1D) risk is genetic. Genetic association has implicated T cells as central to the disease process. Thus, we generated chromatin accessibility profiles from CD4+ T cells isolated from 135 T1D cases and 144 controls and investigated whether (1) there are patterns of chromatin accessibility that differ from T1D patients compared to healthy controls; (2) established T1D risk variants influence chromatin accessibility. Methods: Frozen PBMCs were provided by the Type 1 Diabetes Genetics Consortium (T1DGC). CD4+ T cells were isolated using bead purification and Assay for Transposase Accessible Chromatin (ATAC-seq) was performed. ATAC-seq samples were processed using the PEPATAC pipeline and R packages edgeR and limm. Results: We tested for differences in accessibility between individuals with and without T1D adjusting for sex, age, and experimental variability. We identified 516 chromatin regions peaks with differential accessibility by T1D status (2 with increased and 514 with decreased accessibility at FDR<0.05). Enrichment analysis with the software LOLA indicated these regions are enriched for ETS-1, AP1, and Maf transcription factor binding motifs. Next, we tested for association between T1D-associated variants and chromatin accessibility using available T1DGC genotypes. For each T1D variant with an observed chromatin accessibility quantitative trait locus effect (caQTL), we tested for colocalisation between the two signals and used publicly available expression QTLs (eQTL) to identify potential target genes. We identified six regions where data were consistent with a single variant driving association with T1D risk, chromatin accessibility in CD4+ T cells, and gene expression in whole blood, highlighting several candidate T1D genes: ANKRD55, IL6ST, BACH2, CENPW, SUOX, GDF11, GSDMB, ORMDL3, IKZF3, ERBB2, PNMT. Conclusion: These results provide hypotheses about molecular mechanisms of T1D in CD4+ T cells. Disclosure C.C. Robertson: None. W. Chen: None. S. Onengut-Gumuscu: None. P.J. Concannon: Stock/Shareholder; Self; Amgen. Other Relationship; Self; 10x Genomics. S.S. Rich: None. Funding National Institute of Diabetes and Digestive and Kidney Diseases (DK111906)

Simultaneous Mapping of Molecular Proximity and Comobility Reveals Agonist-Enhanced Dimerization and DNA Binding of Nuclear Receptors.

Single Plane Illumination Microscopy (SPIM) revolutionized time lapse imaging of live cells and organisms due to its high speed and reduced photodamage. Quantitative mapping of molecular (co)mobility by fluorescence (cross-)correlation spectroscopy (F(C)CS) in a SPIM has been introduced to reveal molecular diffusion and binding. A complementary aspect of interactions is proximity, which can be studied by Förster resonance energy transfer (FRET). Here, we extend SPIM-FCCS by alternating laser excitation, which reduces false positive cross-correlation and facilitates comapping of FRET. Thus, different aspects of interacting systems can be studied simultaneously, and molecular subpopulations can be discriminated by multiparameter analysis. After demonstrating the benefits of the method on the AP-1 transcription factor, the dimerization and DNA binding behavior of retinoic acid receptor (RAR) and retinoid X receptor (RXR) is revealed, and an extension of the molecular switch model of the nuclear receptor action is proposed. Our data imply that RAR agonist enhances RAR-RXR heterodimerization, and chromatin binding/dimerization are positively correlated. We also propose a ligand induced conformational change bringing the N-termini of RAR and RXR closer together. The RXR agonist increased homodimerization of RXR suggesting that RXR may act as an autonomous transcription factor.

Involvement of JNK signaling pathway in lipopolysaccharide-induced complement C3 transcriptional activation from amphioxus Branchiostoma belcheri

Complement C3 is a pivotal component of three cascades of complement activation. C3 in circulation is mainly provided by the hepatic cecum. The expression and secretion of C3 by hepatocytes is increased during acute inflammation. The detailed information on the regulationary mechanism underlying C3 transcriptional activation is limited. Here, we characterized the 5′-flanking region of the amphioxus C3 gene. To functionally analyze the upstream regulatory region of the C3 gene, a series of luciferase reporter gene constructs containing deleted or mutant regulatory elements were prepared. Using luciferase assay, we revealed that a potential C-JUN-1 binding sites within the proximal promoter region were necessary for full activation of the C3 promoter, whereas NF-κB, AP-1, C-JUN-2 and NFAT transcription factor binding sites played roles in governing the promoter activity at a homeostatic level. Our data also indicated that sp600125, a c-Jun N-terminal kinase (JNK) inhibitor, decreased lipopolysaccharide (LPS)-stimulated C3 promoter activity, mRNA expression and protein secretion using western blotting and quantitative real-time PCR analysis. These findings demonstrated that JNK signaling pathway is involved in the regulation of C3 gene transcription by targeting C-JUN transcription factor binding sites in the 5′-flanking promoter region, leading to LPS-induced C3 activation and therefore providing a potential target for regulating C3 expression.

Abstract 2926: The regulatory mechanism of human LY6K related to carcinogenesis and metastasis in breast cancer

Abstract The human lymphocyte antigen 6 complex locus K (LY6K) belongs to the lympocyte antigen 6/urokinase-type plasminogen activator receptor (Ly-6/uPAR) superfamily which are associated with development of the immune system and carcinogenesis. LY6K is a cancer biomarker and a therapeutic target that induces invasion and metastasis by activating the Raf-1/MEK/ERK signaling pathway and that stimulates cytotoxic T lymphocytes. However, the molecular mechanisms including genetic and epigenetic that determine human LY6K transcription are complete unknown. To elucidate the genetic mechanisms involved in human LY6K gene regulation and expression, multiple cis elements were predicted using TRANSFAC software, and the LY6K regulatory region was identified using the lucifearse assay in the human LY6K gene promoter. We performed chromatin immunoprecipitation, electrophoretic mobility shift analysis, and supershift assays to investigate the transcription factor activity on the LY6K promoter, and the effect of a single nucleotide polymorphism (SNP) and CpG site methylation on AP-1 transcription factor binding affinity. AP-1 and the CREB transcription factor bound to LY6K promoter within -550/-1, which was essential for LY6K expression but only the AP-1 heterodimer, JunD and Fra-1, modulates LY6K gene transcriptional level. A decrease in LY6K was associated with the SNP242 C allele, a polymorphic G/C-SNP at the 242 nucleotide in the LY6K promoter region (rs2585175), or methylation of the CpG site, which was closely located with the AP-1 site by interfering with binding of the AP-1 transcription factor to the LY6K promoter. In summary, AP-1 activation is important role in promoting LY6K gene expression that regulates cell mobility of breast cancer cells, whereas the SNP242 C allele or methylation of the CpG site may reduce the risk of invasion or metastasis by interfering AP-1 activation. And DNA methylation and histone modification in the 5’-flanking region of the LY6K gene plays an important role in LY6K expression in both breast cancer cells and breast cancer. An understanding of genetic and epigenetic changes in LY6K may contribute to the diagnosis of carcinogenic risk and to an enhanced prediction of outcome in patients with breast cancer. Citation Format: Hyun Kyung Kong, Da Som Son, Jong Hoon Park. The regulatory mechanism of human LY6K related to carcinogenesis and metastasis in breast cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2926.

Functional characterization of the 12p12.1 renal cancer-susceptibility locus implicates BHLHE41.

Genome-wide association studies have identified multiple renal cell carcinoma (RCC) susceptibility loci. Here, we use regional imputation and bioinformatics analysis of the 12p12.1 locus to identify the single-nucleotide polymorphism (SNP) rs7132434 as a potential functional variant. Luciferase assays demonstrate allele-specific regulatory activity and, together with data from electromobility shift assays, suggest allele-specific differences at rs7132434 for AP-1 transcription factor binding. In an analysis of The Cancer Genome Atlas data, SNPs highly correlated with rs7132434 show allele-specific differences in BHLHE41 expression (trend P value=6.3 × 10−7). Cells overexpressing BHLHE41 produce larger mouse xenograft tumours, while RNA-seq analysis reveals that constitutively increased BHLHE41 induces expression of IL-11. We conclude that the RCC risk allele at 12p12.1 maps to rs7132434, a functional variant in an enhancer that upregulates BHLHE41 expression which, in turn, induces IL-11, a member of the IL-6 cytokine family.

HIV-1 Promoter Single Nucleotide Polymorphisms Are Associated with Clinical Disease Severity.

The large majority of human immunodeficiency virus type 1 (HIV-1) markers of disease progression/severity previously identified have been associated with alterations in host genetic and immune responses, with few studies focused on viral genetic markers correlate with changes in disease severity. This study presents a cross-sectional/longitudinal study of HIV-1 single nucleotide polymorphisms (SNPs) contained within the viral promoter or long terminal repeat (LTR) in patients within the Drexel Medicine CNS AIDS Research and Eradication Study (CARES) Cohort. HIV-1 LTR SNPs were found to associate with the classical clinical disease parameters CD4+ T-cell count and log viral load. They were found in both defined and undefined transcription factor binding sites of the LTR. A novel SNP identified at position 108 in a known COUP (chicken ovalbumin upstream promoter)/AP1 transcription factor binding site was significantly correlated with binding phenotypes that are potentially the underlying cause of the associated clinical outcome (increase in viral load and decrease in CD4+ T-cell count).

Leptin increases VEGF expression and enhances angiogenesis in human chondrosarcoma cells

BackgroundLeptin, 16kDa product of obese gene, is adipocytokine playing critical role in regulation of body weight. In recent years, leptin is also defined as potent angiogenic factor involving in tumorigenesis, angiogenesis, and metastasis. However, it is unknown whether leptin regulates VEGF production in human chondrosarcoma and contributing the tumor-associated angiogenesis. MethodsWe analyzed protein level of leptin and VEGF in human chondrosarcoma tissues. Effects of leptin on chondrosarcoma cells were examined by in vitro and in vivo assays. In addition, intracellular signal pathways were investigated by pharmacological and genetic approaches. ResultsWe found that both leptin and VEGF are highly expressed in human chondrosarcoma tissues, and positively correlated with tumor stage. Leptin increases VEGF production by activating OBRl receptor and MAPKs (p38, ERK, and JNK), which in turn enhances binding of AP-1 transcription factor to VEGF promoter, resulting in the transactivation of VEGF expression and subsequently promoting migration and tube formation in endothelial progenitor cells (EPCs). In vivo, knockdown leptin significantly reduces angiogenesis and tumor growth. ConclusionLeptin may be a therapeutic target of angiogenesis and metastasis in chondrosarcoma. General significanceThese findings provide better understanding of pathogenesis of chondrosarcoma and can utilize this knowledge to design new therapeutic strategy.

Eupafolin inhibits PGE2 production and COX2 expression in LPS-stimulated human dermal fibroblasts by blocking JNK/AP-1 and Nox2/p47phox pathway

Eupafolin, a major active component found in the methanol extracts of Phyla nodiflora, has been used to treat inflammation of skin. We examined its effects on cyclooxygenase-2 (COX-2) expression in LPS-treated human dermal fibroblasts. Lipopolysaccharide (LPS) significantly increased prostaglandin-E2 (PGE2) production associated with increased COX-2 expression in Hs68 cells. This effect was blocked by eupafolin, TLR-4 antibody, antioxidants (APO and NAC), as well as inhibitors, including U0126 (ERK1/2), SB202190 (p38), SP600125 (JNK1/2), and Tanshinone IIA (AP-1). In gene regulation level, qPCR and promoter assays revealed that COX-2 expression was attenuated by eupafolin. In addition, eupafolin also ameliorated LPS-induced p47 phox activation and decreased reactive oxygen species (ROS) generation and NADPH oxidase (Nox) activity. Moreover, pretreatment with eupafolin and APO led to reduced LPS-induced phosphorylation of ERK1/2, JNK, and p38. Further, eupafolin attenuated LPS-induced increase in AP-1 transcription factor binding activity as well as the increase in the phosphorylation of c-Jun and c-Fos. In vivo studies have shown that in dermal fibroblasts of LPS treated mice, eupafolin exerted anti-inflammation effects by decreasing COX-2 protein levels. Our results reveal a novel mechanism for anti-inflammatory and anti-oxidative effects of eupafolin that involved inhibition of LPS-induced ROS generation, suppression of MAPK phosphorylation, diminished DNA binding activity of AP-1 and attenuated COX-2 expression leading to reduced production of prostaglandin E2 (PGE2). Our results demonstrate that eupafolin may be used to treat inflammatory responses associated with dermatologic diseases.

A Novel Mutation in the α2-Globin Gene in Two Unrelated Iranian Families

Background: α-globin is encoded by two adjacent genes, αl and α2. Evidence suggests that these genes are not expressed equally and that the α2-globin gene encodes the majority of α-globin. This finding predicts that a thalassemic mutation of the α2-globin gene would result in a more severe loss of α-chain synthesis than a similar mutation in the αl-globin gene. Objectives: In the present study we described a novel non-deletion α-thalassemia defect in the 5'UTR region of the α2-globin gene. Materials and Methods: For molecular analysis, genomic DNA was isolated from peripheral blood cells by a salting out procedure. The common alpha deletion mutations were ruled out using the published primers and conditions. The amplification of the entire β and α1 globin genes was also carried out and their DNA was sequenced. No mutation was detected. Results: The mutation under study was located on an AP-1 transcription factor binding site and inherited in two unrelated Iranian families with hypochromic microcytic anemia. Conclusions: The patients in this study had moderate microcytosis and hypochromia without hemolysis, jaundice and splenomegaly. Molecular analysis in these patients revealed a non-deletion type of mutation in the promoter region, which is highly consistent with findings of other studies.

Elucidation of the mechanism of cell type specific IRF-4-mediated transcription in CD4+ T cells (P1081)

Abstract IL-21 plays a key role in Th17 differentiation. Interferon (IFN) regulatory factor 4 (IRF4) is a critical regulator of differentiation in B and T cells, and Th17 differentiation is defective in Irf4 KO CD4+ T cells. In B cells, IRF4 is known to cooperatively bind DNA in partnership with the Ets family protein PU.1. However, PU.1 is not expressed in most T cells even though IRF4 is active within these cells, and the functional transcription factor complex that regulates Th17-specific genes was not known. Genome-wide Chip-Seq analysis was used to demonstrate that in T cells, IRF4 binds to a novel composite DNA motif that includes AP1 motifs and which we named AP1-IRF4 composite elements (AICEs). Moreover, IL-21-regulated genes in Th17 cells have co-localized binding of IRF4, BATF, and JUN family proteins, and the genes encoding these transcription factors are themselves regulated by IL-21 in CD4+ T cells. RNA-seq analysis revealed subsets of genes whose regulation by IL-21, either positive or negative, depends on IRF4, and reporter studies demonstrated that IL-21-induced transcription of these genes was dependent on both IRF4 and AP1 transcription factor binding. Our results demonstrate that by utilizing distinct binding partners and DNA sequences, IRF4 mediates cell-type and stimulus-specific functions in multiple lymphocyte lineages.

Ochratoxin A-induced cell proliferation and tumor promotion in mouse skin by activating the expression of cyclin-D1 and cyclooxygenase-2 through nuclear factor-kappa B and activator protein-1

Our prior studies have indicated that ochratoxin A (OTA), a mycotoxin, has skin tumor initiating activity. In the present investigation, skin tumor promoting activity of OTA and the mechanism/(s) involved therein was undertaken. A single topical application of OTA (100 nmol/mouse) caused significant enhancement in short-term markers of skin tumor promotion such as ornithine decarboxylase activity, DNA synthesis, hyperplasia as well as expression of cyclin-D1 and COX-2 in mouse skin. In a two-stage mouse skin tumorigenesis protocol, twice-weekly exposure of OTA (50 nmol/mouse) to 7,12-dimethylbenz[α]anthracene (120 nmol/mouse) initiated mice skin for 24 weeks leads to tumor formation. Further, exposure of primary murine keratinocytes (PMKs) with non-cytotoxic dose of OTA (5.0 µM) caused (i) significant enhancement of DNA synthesis, (ii) enhanced phosphorylation and subsequent activation of epidermal growth factor receptor (EGFR) and its downstream signaling pathways viz Akt, ERK1/2, p38 and JNK mitogen-activated protein kinases (MAPKs), (iii) overexpression of c-jun, c-fos, cyclin-D1 and COX-2 and (iv) increased binding of nuclear factor-kappaB (NF-κB) and AP-1 transcription factors to the promoter region of cyclin-D1 and COX-2 genes. It was also observed that knocking down the messenger RNA expression of NF-κB, c-jun, c-fos, cyclin-D1 and COX-2 results in significant inhibition in OTA-induced PMKs proliferation. These results suggest that OTA has cell proliferative and tumor-promoting potential in mouse skin, which involves EGFR-mediated MAPKs and Akt pathways along with NF-κB and AP-1 transcription factors and that cyclin-D1 and COX-2 are the target genes responsible for tumor-promoting activity of OTA.

The Regulatory Mechanism of the LY6K Gene Expression in Human Breast Cancer Cells

LY6K is a cancer biomarker and a therapeutic target that induces invasion and metastasis. However, the molecular mechanisms that determine human LY6K transcription are completely unknown. To elucidate the mechanisms involved in human LY6K gene regulation and expression, multiple cis-elements were predicted using TRANSFAC software, and the LY6K regulatory region was identified using the luciferase assay in the human LY6K gene promoter. We performed ChIP, EMSA, and supershift assays to investigate the transcription factor activity on the LY6K promoter, and the effect of a SNP and CpG site methylation on AP-1 transcription factor binding affinity. AP-1 and the CREB transcription factor bound to LY6K promoter within -550/-1, which was essential for LY6K expression, but only the AP-1 heterodimer, JunD, and Fra-1, modulates LY6K gene transcriptional level. A decrease in LY6K was associated with the SNP242 C allele, a polymorphic G/C-SNP at the 242 nucleotide in the LY6K promoter region (rs2585175), or methylation of the CpG site, which was closely located with the AP-1 site by interfering with binding of the AP-1 transcription factor to the LY6K promoter. Our findings reveal an important role for AP-1 activation in promoting LY6K gene expression that regulates cell mobility of breast cancer cells, whereas the SNP242 C allele or methylation of the CpG site may reduce the risk of invasion or metastasis by interfering AP-1 activation.

MDM2 Promoter SNP344T>A (rs1196333) Status Does Not Affect Cancer Risk

The MDM2 proto-oncogene plays a key role in central cellular processes like growth control and apoptosis, and the gene locus is frequently amplified in sarcomas. Two polymorphisms located in the MDM2 promoter P2 have been shown to affect cancer risk. One of these polymorphisms (SNP309T>G; rs2279744) facilitates Sp1 transcription factor binding to the promoter and is associated with increased cancer risk. In contrast, SNP285G>C (rs117039649), located 24 bp upstream of rs2279744, and in complete linkage disequilibrium with the SNP309G allele, reduces Sp1 recruitment and lowers cancer risk. Thus, fine tuning of MDM2 expression has proven to be of significant importance with respect to tumorigenesis. We assessed the potential functional effects of a third MDM2 promoter P2 polymorphism (SNP344T>A; rs1196333) located on the SNP309T allele. While in silico analyses indicated SNP344A to modulate TFAP2A, SPIB and AP1 transcription factor binding, we found no effect of SNP344 status on MDM2 expression levels. Assessing the frequency of SNP344A in healthy Caucasians (n = 2,954) and patients suffering from ovarian (n = 1,927), breast (n = 1,271), endometrial (n = 895) or prostatic cancer (n = 641), we detected no significant difference in the distribution of this polymorphism between any of these cancer forms and healthy controls (6.1% in healthy controls, and 4.9%, 5.0%, 5.4% and 7.2% in the cancer groups, respectively). In conclusion, our findings provide no evidence indicating that SNP344A may affect MDM2 transcription or cancer risk.

Abstract 2203: AP-1 activation and a functional SNP242 regulates the LY-6K gene expression in human breast cancer cells

Abstract Background: Lymphocyte antigen 6 complex locus K(LY-6K), a member of LY-6/uPAR receptor superfamily and cancer-testis antigen, is a novel breast cancer biomarker. Also LY-6K is target antigen for the head and neck squamous cell carcinoma, and lung and esophageal carcinoma. Elevated LY-6K induces cell invasion and metastasis through activating the Raf-1/MEK/ERK signaling pathway. However, the molecular mechanisms that mediate regulation of human LY-6K gene expression are completely unknown. Material and Methods: Within the pGL3-basic reporter vector, the −3050/+182 bp fragment, truncated and mutated fragment upstream of the LY-6K gene was subcloned and measured promoter activity. Subsequently, multiple cis elements were identified using several gene tool software (TFSEARCH, TRANSFAC, PROMO and MATCHTM) in the promoter of human LY-6K gene. We investigated the transcription factor and the effect of single nucleotide polymorphism (SNP) on LY-6K promoter activity and transcription factor binding using chromatin immunoprecipitation (ChIP) assays, electrophoretic mobility shift assays (EMSA), and supershift assays. Results: LY-6K gene was expressed in estrogen receptor (ERα) and progesterone receptor (PR)-negative breast cancer cell lines. A novel AP-1 binding site in the LY-6K promoter regulates LY-6K gene expression. A polymorphic C/G-SNP at the 242 nucleotide position in the promoter region (rs2585175, called SNP242) was validated to be located in a PAX-3 transcription binding motif, which is appear with the presence of the G-allele resulting in a ∼54% decrease in LY-6K promoter activity by interfering binding of AP-1 transcription factor. Discussion: The activity of the AP-1 transcription factor plays an important role in cell mobility of breast cancer cells via the promoting of LY-6K gene expression. LY-6K expression is dependent on not AP-1 transcription factor, but also functional SNP242 G-allele. These results suggested that the polymorphism rs2585175 (SNP242), in close proximity of the LY-6K promoter, lead to LY-6K downregulation, and thus, may reduce the risk of breast cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2203. doi:1538-7445.AM2012-2203

ERK activation is required for PGE2-induced MMP-9 production in bone-morrow derived DCs (112.23)

Abstract Dendritic Cells (DCs) play an important role in the initiation of the immune response. Immature DCs take up antigen, mature and migrate to the regional lymph nodes where they activate antigen-specific naïve T cells. Prostaglandins such as PGE2 are essential for the migration of DCs to lymph nodes. Matrix metalloproteinases (MMPs) play an essential role in DC migration, through the degradation of extracellular matrix (ECM) and basement membranes. MMP2, and particularly MMP9, are essential for dendritic cell migration in vitro, as well as in vivo to the draining lymph nodes. In this study, we show that PGE2-induced MMP9 expression is mediated through the EP2/EP4-cAMP-PKA/PI3K-ERK signaling pathway. EP2 and EP4 receptors as well as cAMP analog mimic the effect of PGE2 to upregulate MMP-9. In the presence of PKA, PI3K or ERK inhibitors, PGE2-induced MMP-9 production is abolished. Furthermore, PGE2-induced c-Fos expression mediated through ERK activation is required for the binding of AP-1 transcription factor to the MMP-9 promoter. In the presence of ERK inhibitors, PGE2-induced AP-1 binding is abrogated. Our results describe a new molecular mechanism for the effect of PGE on MMP-9 production in DCs, which could lead to a new therapeutic approach by using ERK inhibitors to regulate DC migration.

Construction of Iuciferase reporter vectors harboring DC-SIGN promoters without AP-1 or ETS-1 transcription factor binding site and detection of their activity

Objective To detect the role of AP-1 or ETS-1 transcription factor binding sites (TFBS) in activity of DC-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN) pro-moter. Methods Genomic DNA was extracted from peripheral blood. Complete DC-SIGN promoter and those without AP-1 or ETS-1 TFBS were amplified by PCR using designed primers. The PCR products were digested with MLu Ⅰ and Bgl Ⅱ and then ligated into MLu Ⅰ and Bgl Ⅱ digested pGL-3/Basic and pGL-3/En-hancer vectors. Transfection in Hacat and 293 cells was accomplished with Trans Fast liposome. Activity of luciferase was detected after 48 h. Results The DC-SIGN promoters without AP-1 or ETS-1 TFBS and the recombined pGL-3 vectors were correctly constructed. The activity of DC-SIGN promoters without AP-1 was reduced 20% (293) and 10% (Hacat), which was 40%-50% with enhancer. The activity of DC-SIGN pro-moters without ETS-1 was nearly vanished, no matter with or without enhancer. Conclusion ETS-1 TFBS, not AP-1 TFBS, plays an important role in activity of DC-SIGN promoter. Key words: HIV; DC-SIGN; Promoter; Transcription factor binding site; Reporter vector

Overexpression of Protease-Activated Receptor-1 Contributes to Melanoma Metastasis via Regulation of Connexin 43

Protease-activated receptor-1 (PAR-1) is a key player in melanoma metastasis with higher expression seen in metastatic melanoma cell lines and tissue specimens. cDNA microarray and Western blot analyses reveal that the gap junctional intracellular communication molecule connexin 43 (Cx-43), known to be involved in tumor cell diapedesis and attachment to endothelial cells, is significantly decreased after PAR-1 silencing in metastatic melanoma cell lines. Furthermore, Cx-43 promoter activity was significantly inhibited in PAR-1-silenced cells, suggesting that PAR-1 regulates Cx-43 at the transcriptional level. Chromatin immunoprecipitation studies showed a reduction in the binding of SP-1 and AP-1 transcription factors to the promoter of Cx-43. Both transcription factors have been shown previously to be required for maximal Cx-43 promoter activity. These results were corroborated by mutating the AP-1 and SP-1 binding sites resulting in decreased Cx-43 promoter activity in PAR-1-positive cells. Moreover, as Cx-43 has been shown to facilitate arrest of circulating tumor cells at the vascular endothelium, melanoma cell attachment to endothelial cells was significantly decreased in PAR-1-silenced cells, with this effect being abrogated after PAR-1 rescue. Herein, we report that up-regulation of PAR-1 expression, seen in melanoma progression, mediates high levels of Cx-43 expression. As both SP-1 and AP-1 transcription factors act as positive regulators of Cx-43, our data provide a novel mechanism for the regulation of Cx-43 expression by PAR-1. Indeed, Cx-43 expression was restored following PAR-1 rescue in PAR-1-silenced cells. Taken together, our data support the tumor promoting function of Cx-43 in melanoma.

AP-1 and ERK1 but not p38 nor JNK is required for CRPV early protein 2-dependent MMP-9 promoter activation in rabbit epithelial cells

Human papillomaviruses (HPV) are the known cause for a variety of cancers including cervical and epithelial cancers. The cottontail-rabbit papillomavirus (CRPV) serves as a suitable animal model to study the development of these cancers in vivo. We have previously demonstrated that CRPV-induced skin carcinomas express high levels of MMP-9, a metalloproteinase contributing to cancer progression by extracellular matrix remodelling. Based on our previously reported finding that CRPV early protein 2 can activate a truncated human 670 bp MMP-9 promoter fragment, we hypothesized that MMP-9 expression in the rabbit carcinomas is a consequence of activation of the rabbit MMP-9 promoter in-trans by CRPV early protein 2. Further elucidation of the mechanism revealed the requirement for both a proximal and distal AP-1 transcription factor binding site in the rabbit MMP-9 promoter and the AP-1 complex as demonstrated by the inhibitory effect of TAM67, a trans-activation deficient c-jun mutant. The characterization of signal-transduction requirements revealed predominantly ERK1 to be required for CRPV early protein 2-dependent MMP-9 promoter activation, but not JNK nor p38. In summary CRPV early protein 2 activates the expression of MMP-9 in-trans through AP-1 and ERK1 and may contribute to cancer development and progression via this mechanism within the animal model.

Lysyl oxidase like 4, a novel target gene of TGF-β1 signaling, can negatively regulate TGF-β1-induced cell motility in PLC/PRF/5 hepatoma cells

Transforming growth factor-β1 (TGF-β1) is a multi-functional cytokine involved in the regulation of cell proliferation, differentiation and extracellular matrix formation. In search for novel genes mediating the TGF-β1 function at downstream signaling, we performed a cDNA microarray analysis and identified 60 genes whose expression is regulated by TGF-β1 in the liver cancer cell line PLC/PRF/5. Among them, we report here lysyl oxidase like 4 (LOXL4) as a novel target of TGF-β1 signaling, and provide experimental evidence for its expression regulation and function. LOXL4 was found to be the only member of LOX family whose expression is induced by TGF-β1 in hepatoma cells. Deletion mapping of the LOXL4 promoter indicated that the TGF-β1 regulation of LOXL4 expression is mediated through the binding of AP1 transcription factor to a conserved region of the promoter. This was confirmed by the chromatin immunoprecipitation assay that captured c-Fos-bound chromatin from TGF-β1-treated cells. Forced expression of LOXL4 in PLC/PRF/5 cells resulted in inhibition of cell motility through Matrigel in the presence of TGF-β1 treatment. In parallel, LOXL4 suppressed the expression of laminins and α3 integrin and the activity of MMP2. These results suggest that LOXL4 may function as a negative feedback regulator of TGF-β1 in cell invasion by inhibiting the metabolism of extracellular matrix (ECM) components.