Identification of mouse Jun dimerization protein 2 as a novel repressor of ATF-2

The AHR-NRF2-JDP2 gene battery: Ligand-induced AHR transcriptional activation

Aryl hydrocarbon receptor (AHR) and nuclear factor-erythroid 2-related factor 2 (NRF2) can regulate a series of genes encoding the detoxifying phase I and II enzymes, via a signaling crosstalk known as the "AHR-NRF2 gene battery". The chromatin transcriptional regulator Jun dimerization protein 2 (JDP2) plays a central role in thetranscription of AHR gene in response to the phase I enzyme ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin. It forms a transcriptional complex with AHR-AHR nuclear translocator (ARNT) and NRF2-small musculoaponeurotic fibrosarcoma proteins (sMAF), which are then recruited to the respective cis-elements, such as dioxin response elements and antioxidant response elements, respectively, in the AHR promoter. Here, we present a revised description of the AHR-NRF2 gene battery as the AHR-NRF2-JDP2 gene battery for transactivating the AHR promoter by phase I enzyme ligands. The chromatin regulator JDP2 was found to be involved in the movement of AHR-NRF2 complexes from the dioxin response element to the antioxidant response element in the AHR promoter, during its activation in a spatiotemporal manner. This new epigenetic and chromatin remodeling role of AHR-NRF2-JDP2 axis is useful for identifying new therapeutic targets for various diseases, including immunological response, detoxification, development, and cancer-related diseases.

Candidate plasticity gene 16 and jun dimerization protein 2 are involved in the suppression of insulin gene expression in rat pancreatic INS-1 β-cells

Chronic hyperglycemia causes pancreatic β-cell dysfunction, impaired insulin secretion and the suppression of insulin gene expression. This phenomenon is referred to as glucotoxicity, and is a critical component of the pathogenesis of type 2 diabetes. We previously reported that the expression of candidate plasticity gene 16 (CPG16) was higher in rat pancreatic INS-1 β-cells under glucotoxic conditions and CPG16 suppressed insulin promoter activity. However, the molecular mechanisms of the CPG16-mediated suppression of insulin gene expression are unclear. In this study, we found that CPG16 directly bound and phosphorylated jun dimerization protein 2 (JDP2), an AP-1 family transcription factor. CPG16 co-localized with JDP2 in the nucleus of INS-1 cells. JDP2 bound to the G1 element of the insulin promoter and up-regulated promoter activity. Finally, CPG16 suppressed the up-regulation of insulin promoter activity by JDP2 in a kinase activity-dependent manner. These results suggest that CPG16 suppresses insulin promoter activity by phosphorylating JDP2.

JDP2, a Novel Molecular Key in Heart Failure and Atrial Fibrillation?

Heart failure (HF) and atrial fibrillation (AF) are two major life-threatening diseases worldwide. Causes and mechanisms are incompletely understood, yet current therapies are unable to stop disease progression. In this review, we focus on the contribution of the transcriptional modulator, Jun dimerization protein 2 (JDP2), and on HF and AF development. In recent years, JDP2 has been identified as a potential prognostic marker for HF development after myocardial infarction. This close correlation to the disease development suggests that JDP2 may be involved in initiation and progression of HF as well as in cardiac dysfunction. Although no studies have been done in humans yet, studies on genetically modified mice impressively show involvement of JDP2 in HF and AF, making it an interesting therapeutic target.

Genotoxic stress-triggered β-catenin/JDP2/PRMT5 complex facilitates reestablishing glutathione homeostasis

The mechanisms underlying how cells subjected to genotoxic stress reestablish reduction-oxidation (redox) homeostasis to scavenge genotoxic stress-induced reactive oxygen species (ROS), which maintains the physiological function of cellular processes and cell survival, remain unclear. Herein, we report that, via a TCF-independent mechanism, genotoxic stress induces the enrichment of β-catenin in chromatin, where it forms a complex with ATM phosphorylated-JDP2 and PRMT5. This elicits histone H3R2me1/H3R2me2s-induced transcriptional activation by the recruitment of the WDR5/MLL methyltransferase complexes and concomitant H3K4 methylation at the promoters of multiple genes in GSH-metabolic cascade. Treatment with OICR-9429, a small-molecule antagonist of the WDR5-MLL interaction, inhibits the β-catenin/JDP2/PRMT5 complex-reestablished GSH metabolism, leading to a lethal increase in the already-elevated levels of ROS in the genotoxic-agent treated cancer cells. Therefore, our results unveil a plausible role for β-catenin in reestablishing redox homeostasis upon genotoxic stress and shed light on the mechanisms of inducible chemotherapy resistance in cancer.

It is known that genotoxic stress induces high levels of ROS and deplete cellular glutathione stores. Here, Cao et al. uncover a β-catenin-dependent TCF/LEF-independent mechanism that promotes histone-mediated transcriptional activation of glutathione synthesis.

JDP2 and ATF3 deficiencies dampen maladaptive cardiac remodeling and preserve cardiac function

c-Jun dimerization protein (JDP2) and Activating Transcription Factor 3 (ATF3) are closely related basic leucine zipper proteins. Transgenic mice with cardiac expression of either JDP2 or ATF3 showed maladaptive remodeling and cardiac dysfunction. Surprisingly, JDP2 knockout (KO) did not protect the heart following transverse aortic constriction (TAC). Instead, the JDP2 KO mice performed worse than their wild type (WT) counterparts. To test whether the maladaptive cardiac remodeling observed in the JDP2 KO mice is due to ATF3, ATF3 was removed in the context of JDP2 deficiency, referred as double KO mice (dKO). Mice were challenged by TAC, and followed by detailed physiological, pathological and molecular analyses. dKO mice displayed no apparent differences from WT mice under unstressed condition, except a moderate better performance in dKO male mice. Importantly, following TAC the dKO hearts showed low fibrosis levels, reduced inflammatory and hypertrophic gene expression and a significantly preserved cardiac function as compared with their WT counterparts in both genders. Consistent with these data, removing ATF3 resumed p38 activation in the JDP2 KO mice which correlates with the beneficial cardiac function.

Collectively, mice with JDP2 and ATF3 double deficiency had reduced maladaptive cardiac remodeling and lower hypertrophy following TAC. As such, the worsening of the cardiac outcome found in the JDP2 KO mice is due to the elevated ATF3 expression. Simultaneous suppression of both ATF3 and JDP2 activity is highly beneficial for cardiac function in health and disease.

ATF3 and JDP2 deficiency in cancer associated fibroblasts promotes tumor growth via SDF-1 transcription

The activating transcription factor 3 (ATF3) and the c-Jun dimerization protein 2 (JDP2) are members of the basic leucine zipper (bZIP) family of transcription factors. These proteins share a high degree of homology and both can activate or repress transcription. Deficiency of either one of them in the non-cancer host cells was shown to reduce metastases. As ATF3 and JDP2 compensate each other's function, we studied the double deficiency of ATF3 and JDP2 in the stromal tumor microenvironment. Here, we show that mice with ATF3 and JDP2 double deficiency (designated thereafter dKO) developed larger tumors with high vascular perfusion and increased cell proliferation rate compared to wild type (WT) mice. We further identify that the underlying mechanism involves tumor associated fibroblasts which secrete high levels of stromal cell-derived factor 1 (SDF-1) in dKO fibroblasts. SDF-1 depletion in dKO fibroblasts dampened tumor growth and blood vessel perfusion. Furthermore, ATF3 and JDP2 were found to regulate SDF-1 transcription and secretion in fibroblasts, a phenomenon that is potentiated in the presence of cancer cells. Collectively, our results suggest that ATF3 and JDP2 regulate the expression of essential tumor promoting factors expressed by fibroblasts within the tumor microenvironment, and thus restrain tumor growth.

Fipronil-induced toxic effects in zebrafish (Danio rerio) larvae by using digital gene expression profiling

Fipronil residue has caused widespread concern around the world, especially after the recent "toxic eggs" event in seven European countries. To evaluate the effects of fipronil on vertebrates, zebrafish larvae were used as an animal model to examine the lethal effect, developmental phenotypes at high doses, and possible mechanisms of toxicity by employing digital gene expression (DGE) profiling at environmentally relevant doses. The results of acute toxicity test indicated that treatment with fipronil from 75 h post-fertilization (hpf) led to the death of larvae with a 96-h LC50 value of 459 μg/L, as well as abnormal development including bent spine and shortened body length. Besides, we obtained high-quality-sequencing DGE profilings at fipronil concentrations of 0.5, 5, and 50 μg/L, respectively. The results revealed that 44 differentially expressed genes, 10 GO terms, and 3 KEGG pathways were overlapped among the three concentrations. MIDN, one of the 44 differentially expressed genes, showed dose-dependent responses at the transcriptional level, indicating that it was possibly a potential biomarker to reflect fipronil toxicity in zebrafish. Furthermore, we presumed that the changing transcriptional level of AP-1 family was possibly a reason for bent spine and shortened body length in larvae exposed to fipronil. Concurrently, altered abundance of transcripts of the ELOVL family in a key step of fatty acid elongation could possibly lead to the accumulation of long-chain fatty acids. Collectively, our results suggested that exposure to fipronil caused lethal and developmental toxicity in zebrafish larvae, and demonstrated the need for a comprehensive understanding of the potential mechanisms of fipronil toxicity due to fipronil's frequent presence in the environment and its potential threat to human health.

JDP2 overexpression provokes cardiac dysfunction in mice

The transcriptional regulator JDP2 (Jun dimerization protein 2) has been identified as a prognostic marker for patients to develop heart failure after myocardial infarction. We now performed in vivo studies on JDP2-overexpressing mice, to clarify the impact of JDP2 on heart failure progression. Therefore, during birth up to the age of 4 weeks cardiac-specific JDP2 overexpression was prevented by doxycycline feeding in transgenic mice. Then, JDP2 overexpression was started. Already after 1 week, cardiac function, determined by echocardiography, decreased which was also resembled on the cardiomyocyte level. After 5 weeks blood pressure declined, ejection fraction and cardiac output was reduced and left ventricular dilatation developed. Heart weight/body weight, and mRNA expression of ANP, inflammatory marker genes, collagen and fibronectin increased. Collagen 1 protein expression increased, and fibrosis developed. As an additional sign of elevated extracellular matrix remodeling, matrix metalloproteinase 2 activity increased in JDP2 mice. Thus, JDP2 overexpression is deleterious to heart function in vivo. It can be concluded that JDP2 overexpression provokes cardiac dysfunction in adult mice that is accompanied by hypertrophy and fibrosis. Thus, induction of JDP2 is a maladaptive response contributing to heart failure development.

FACS-Seq analysis of Pax3-derived cells identifies non-myogenic lineages in the embryonic forelimb

Skeletal muscle in the forelimb develops during embryonic and fetal development and perinatally. While much is known regarding the molecules involved in forelimb myogenesis, little is known about the specific mechanisms and interactions. Migrating skeletal muscle precursor cells express Pax3 as they migrate into the forelimb from the dermomyotome. To compare gene expression profiles of the same cell population over time, we isolated lineage-traced Pax3⁺ cells (Pax3^EGFP) from forelimbs at different embryonic days. We performed whole transcriptome profiling via RNA-Seq of Pax3⁺ cells to construct gene networks involved in different stages of embryonic and fetal development. With this, we identified genes involved in the skeletal, muscular, vascular, nervous and immune systems. Expression of genes related to the immune, skeletal and vascular systems showed prominent increases over time, suggesting a non-skeletal myogenic context of Pax3-derived cells. Using co-expression analysis, we observed an immune-related gene subnetwork active during fetal myogenesis, further implying that Pax3-derived cells are not a strictly myogenic lineage, and are involved in patterning and three-dimensional formation of the forelimb through multiple systems.

Downregulation of Ap-1 Repressor Jdp2 is Associated with Tumor Metastasis and Poor Prognosis in Patients with Pancreatic Carcinoma

Pancreatic carcinoma is one of the most malignant and aggressive cancers. The identification of prognostic factors is thought to be useful in directing treatment. Transcription factor Jun dimerization protein 2 (JDP2), a member of the activator protein 1 (AP-1) family, acts as an AP-1 inhibitor and has been implicated in many cellular processes including carcinogenesis. The role of JDP2 in the development of pancreatic carcinoma, however, remained elusive. In this study we examined the expression levels of JDP2 in 36 pancreatic carcinoma samples by Western blotting and found that JDP2 expression was significantly downregulated in pancreatic carcinoma samples compared with peritumoral tissues. The decrease in JDP2 expression was correlated with lymph node metastasis and distant metastasis and strongly associated with the post-surgery survival time. These results indicate a possible connection between JDP2 expression and metastasis in pancreatic carcinoma and suggest that JDP2 can serve as a biomarker to predict the prognosis of patients with this cancer.

MicroRNA-30b controls endothelial cell capillary morphogenesis through regulation of transforming growth factor beta 2

The importance of microRNA (miRNA) to vascular biology is becoming increasingly evident; however, the function of a significant number of miRNA remains to be determined. In particular, the effect of growth factor regulation of miRNAs on endothelial cell morphogenesis is incomplete. Thus, we aimed to identify miRNAs regulated by pro-angiogenic vascular endothelial growth factor (VEGF) and determine the effects of VEGF-regulated miRNAs and their targets on processes important for angiogenesis. Human umbilical vein endothelial cells (HUVECs) were thus stimulated with VEGF and miRNA levels assessed using microarrays. We found that VEGF altered expression of many miRNA, and for this study focused on one of the most significantly down-regulated miRNA in HUVECs following VEGF treatment, miR-30b. Using specific miRNA mimics, we found that overexpression of miR-30b inhibited capillary morphogenesis in vitro, while depletion of endogenous miR-30b resulted in increased capillary morphogenesis indicating the potential significance of down-regulation of miR-30b as a pro-angiogenic response to VEGF stimulation. MiR-30b overexpression in HUVEC regulated transforming growth factor beta 2 (TGFβ2) production, which led to increased phosphorylation of Smad2, indicating activation of an autocrine TGFβ signaling pathway. Up-regulation of TGFβ2 by miR-30b overexpression was found to be dependent on ATF2 activation, a transcription factor known to regulate TGFβ2 expression, as miR-30b overexpressing cells exhibited increased levels of phosphorylated ATF2 and depletion of ATF2 inhibited miR-30b-induced TGFβ2 expression. However, miR-30b effects on ATF2 were indirect and found to be via targeting of the known ATF2 repressor protein JDP2 whose mRNA levels were indirectly correlated with miR-30b levels. Increased secretion of TGFβ2 from HUVEC was shown to mediate the inhibitory effects of miR-30b on capillary morphogenesis as treatment with a neutralizing antibody to TGFβ2 restored capillary morphogenesis to normal levels in miR-30b overexpressing cells. These results support that the regulation of miR-30b by VEGF in HUVEC is important for capillary morphogenesis, as increased miR-30b expression inhibits capillary morphogenesis through enhanced expression of TGFβ2.

c-JUN Dimerization Protein 2 (JDP2) Is a Transcriptional Repressor of Follicle-stimulating Hormone β (FSHβ) and Is Required for Preventing Premature Reproductive Senescence in Female Mice

Follicle-stimulating hormone (FSH) regulates follicular growth and stimulates estrogen synthesis in the ovaries. FSH is a heterodimer consisting of an α subunit, also present in luteinizing hormone, and a unique β subunit, which is transcriptionally regulated by gonadotropin-releasing hormone 1 (GNRH). Because most FSH is constitutively secreted, tight transcriptional regulation is critical for maintaining FSH levels within a narrow physiological range. Previously, we reported that GNRH induces FSHβ (Fshb) transcription via induction of the AP-1 transcription factor, a heterodimer of c-FOS and c-JUN. Herein, we identify c-JUN-dimerization protein 2 (JDP2) as a novel repressor of GNRH-mediated Fshb induction. JDP2 exhibited high basal expression and bound the Fshb promoter at an AP-1-binding site in a complex with c-JUN. GNRH treatment induced c-FOS to replace JDP2 as a c-JUN binding partner, forming transcriptionally active AP-1. Subsequently, rapid c-FOS degradation enabled reformation of the JDP2 complex. In vivo studies revealed that JDP2 null male mice have normal reproductive function, as expected from a negative regulator of the FSH hormone. Female JDP2 null mice, however, exhibited early puberty, observed as early vaginal opening, larger litters, and early reproductive senescence. JDP2 null females had increased levels of circulating FSH and higher expression of the Fshb subunit in the pituitary, resulting in elevated serum estrogen and higher numbers of large ovarian follicles. Disruption of JDP2 function therefore appears to cause early cessation of reproductive function, a condition that has been associated with elevated FSH in women.

Host JDP2 expression in the bone marrow contributes to metastatic spread

The c-Jun Dimerization Protein 2, JDP2, is a basic leucine zipper protein member of the activator protein-1 (AP-1) family of transcription factors. JDP2 typically suppresses gene transcription through multiple mechanisms and plays a dual role in multiple cellular processes, including cell differentiation and proliferation which is dependent on AP-1 function. Whereas the role of JDP2 expression within cancer cells has been studied, its role in stromal cells at the tumor microenvironment is largely unknown. Here we show that mice lacking JDP2 (JDP2−/−) display a reduced rate of metastasis in Lewis lung carcinoma (LLC) and polyoma middle T-antigen (PyMT) breast carcinoma mouse models. The replacement of wild-type bone marrow derived cells (BMDCs) with JDP2-deficient BMDCs recapitulates the metastatic phenotype of JDP2−/− tumor-bearing mice. In vitro, conditioned medium of wild-type BMDCs significantly potentiates the migration and invasion capacity of LLC cells as compared to that of JDP2−/− BMDCs. Furthermore, wild-type BMDCs secrete CCL5, a chemokine known to contribute to metastasis, to a greater extent than JDP2−/− BMDCs. The supplementation of CCL5 in JDP2−/− BMDC conditioned medium was sufficient to potentiate the invasion capacity of LLC. Overall, this study suggests that JDP2-expressing BMDCs within the tumor microenvironment contribute to metastatic spread.

Multiple functions of the histone chaperone Jun dimerization protein 2

The Jun dimerization protein 2 (JDP2) is part of the family of stress-responsible transcription factors such as the activation protein-1, and binds the 12-O-tetradecanoylphorbol-13-acetateresponse element and the cAMP response element. It also plays a role as a histone chaperone and participates in diverse processes, such as cell-cycle arrest, cell differentiation, apoptosis, senescence, and metastatic spread, and functions as an oncogene and anti-oncogene, and as a cellular reprogramming factor. However, the molecular mechanisms underlying these multiple functions of JDP2 have not been clarified. This review summarizes the structure and function of JDP2, highlighting the specific role of JDP2 in cellular-stress regulation and prevention.

CARMA1- and MyD88-dependent activation of Jun/ATF-type AP-1 complexes is a hallmark of ABC diffuse large B-cell lymphomas

A hallmark of the diffuse large B-cell lymphoma (DLBCL) of the activated B-cell (ABC) type, a molecular subtype characterized by adverse outcome, is constitutive activation of the transcription factor nuclear factor-κB (NF-κB), which controls expression of genes promoting cellular survival and proliferation. Much less, however, is known about the role of the transcription factor activator protein-1 (AP-1) in ABC DLBCL. Here, we show that AP-1, like NF-κB, was controlled by constitutive activation of the B-cell receptor signaling component caspase recruitment domain-containing membrane-associated guanylate kinase 1 (CARMA1) and/or the Toll-like receptor signaling component myeloid differentiation primary response gene 88 (MyD88) in ABC DLBCL cell lines. In contrast to germinal center (GC) B-cell (GCB) DLBCL, ABC DLBCL cell lines expressed high levels of the AP-1 family members c-Jun, JunB, and JunD, which formed heterodimeric complexes with the AP-1 family members activating transcription factor (ATF) 2, ATF3, and ATF7. Inhibition of these complexes by a dominant-negative approach led to impaired growth of a majority of ABC DLBCL cell lines. Individual silencing of c-Jun, ATF2, or ATF3 decreased cellular survival and revealed c-Jun/ATF2-dependent control of ATF3 expression. As a consequence, ATF3 expression was much higher in ABC vs GCB DLBCL cell lines. Samples derived from DLBCL patients showed a clear trend toward high and nuclear ATF3 expression in nodal DLBCL of the non-GC or ABC subtype. These findings identify the activation of AP-1 complexes of the Jun/ATF-type as an important element controlling the growth of ABC DLBCL.

ATF3-dependent cross-talk between cardiomyocytes and macrophages promotes cardiac maladaptive remodeling

RATIONALE

Pressure overload induces adaptive remodeling processes in the heart. However, when pressure overload persists, adaptive changes turn into maladaptive alterations leading to cardiac hypertrophy and heart failure. ATF3 is a stress inducible transcription factor that is transiently expressed following neuroendocrine stimulation. However, its role in chronic pressure overload dependent cardiac hypertrophy is currently unknown.

OBJECTIVE

The objective of the study was to study the role of ATF3 in chronic pressure overload dependent cardiac remodeling processes.

METHODS AND RESULTS

Pressure overload was induced by phenylephrine (PE) mini-osmotic pumps in various mice models of whole body, cardiac specific, bone marrow (BM) specific and macrophage specific ATF3 ablations. We show that ATF3-KO mice exhibit a significantly reduced expression of cardiac remodeling markers following chronic pressure overload. Consistently, the lack of ATF3 specifically in either cardiomyocytes or BM derived cells blunts the hypertrophic response to PE infusion. A unique cross-talk between cardiomyocytes and macrophages was identified. Cardiomyocytes induce an ATF3 dependent induction of an inflammatory response leading to macrophage recruitment to the heart. Adoptive transfer of wild type macrophages, but not ATF3-KO derived macrophages, into wild type mice potentiates maladaptive response to PE infusion.

CONCLUSIONS

Collectively, this study places ATF3 as a key regulator in promoting pressure overload induced cardiac hypertrophy through a cross-talk between cardiomyocytes and macrophages. Inhibiting this cross-talk may serve as a useful approach to blunt maladaptive remodeling processes in the heart.

Emerging molecules in the interface between skeletal system and innate immunity

Despite the improved treatment of bone destruction, significant unmet medical need remains. For example, there is a limited benefit of continued bisphosphonate therapy for osteoporotic patients, and only minor populations of rheumatoid arthritis patients obtain biologic-free remission. Therefore, the identification of a novel therapeutic target for bone destructive diseases remains an important issue in the field of skeletal biology. To date there has been little progress in identifying osteo-innate-immunological regulators that could be used for the prophylactic treatment of inflammatory bone destruction. Recently, we identified several new molecules that are critical osteo-innate-immunological regulators by using gene targeting technology. These findings may offer an invaluable opportunity to regulate bone-destructive diseases, such as osteoporosis and rheumatoid arthritis.

Cdk1-mediated phosphorylation of human ATF7 at Thr-51 and Thr-53 promotes cell-cycle progression into M phase

Activating transcription factor 2 (ATF2) and its homolog ATF7 are phosphorylated at Thr-69/Thr-71 and at Thr-51/Thr-53, respectively, by stress-activated MAPKs regulating their transcriptional functions in G1 and S phases. However, little is known about the role of ATF2 and ATF7 in G2/M phase. Here, we show that Cdk1-cyclin B1 phosphorylates ATF2 at Thr-69/Thr-71 and ATF7 at Thr-51/Thr-53 from early prophase to anaphase in the absence of any stress stimulation. Knockdown of ATF2 or ATF7 decreases the rate of cell proliferation and the number of cells in M-phase. In particular, the knockdown of ATF7 severely inhibits cell proliferation and G2/M progression. The inducible expression of a mitotically nonphosphorylatable version of ATF7 inhibits G2/M progression despite the presence of endogenous ATF7. We also show that mitotic phosphorylation of ATF7 promotes the activation of Aurora kinases, which are key enzymes for early mitotic events. These results suggest that the Cdk1-mediated phosphorylation of ATF7 facilitates G2/M progression, at least in part, by enabling Aurora signaling.

Cloning and characterization of the mouse JDP2 gene promoter reveal negative regulation by p53

Jun dimerization protein 2 (JDP2) is a repressor of transcription factor AP-1. To investigate the transcriptional regulation of the JDP2 gene, we cloned the 5'-flanking region of the mouse JDP2 gene. Primer extension analysis revealed a new transcription start site (+1). Promoter analysis showed that the region from nt -343 to nt +177 contains basal transcriptional activity. Interestingly, the tumor suppressor p53 significantly repressed the transcriptional activity of the JDP2 promoter. Given that JDP2 inhibits expression of p53, our results suggest a negative feedback loop between JDP2 and p53, and a direct link between JDP2 and a key oncogenic pathway.

Jun dimerization protein 2 is a critical component of the Nrf2/MafK complex regulating the response to ROS homeostasis

Oxidative stress and reactive oxygen species (ROS) are associated with diseases such as cancer, cardiovascular complications, inflammation and neurodegeneration. Cellular defense systems must work constantly to control ROS levels and to prevent their accumulation. We report here that the Jun dimerization protein 2 (JDP2) has a critical role as a cofactor for transcription factors nuclear factor-erythroid 2-related factor 2 (Nrf2) and small Maf protein family K (MafK) in the regulation of the antioxidant-responsive element (ARE) and production of ROS. Chromatin immunoprecipitation–quantitative PCR (qPCR), electrophoresis mobility shift and ARE-driven reporter assays were carried out to examine the role of JDP2 in ROS production. JDP2 bound directly to the ARE core sequence, associated with Nrf2 and MafK (Nrf2–MafK) via basic leucine zipper domains, and increased DNA-binding activity of the Nrf2–MafK complex to the ARE and the transcription of ARE-dependent genes. In mouse embryonic fibroblasts from Jdp2-knockout (Jdp2 KO) mice, the coordinate transcriptional activation of several ARE-containing genes and the ability of Nrf2 to activate expression of target genes were impaired. Moreover, intracellular accumulation of ROS and increased thickness of the epidermis were detected in Jdp2 KO mice in response to oxidative stress-inducing reagents. These data suggest that JDP2 is required to protect against intracellular oxidation, ROS activation and DNA oxidation. qPCR demonstrated that several Nrf2 target genes such as heme oxygenase-1, glutamate–cysteine ligase catalytic and modifier subunits, the notch receptor ligand jagged 1 and NAD(P)H dehydrogenase quinone 1 are also dependent on JDP2 for full expression. Taken together, these results suggest that JDP2 is an integral component of the Nrf2–MafK complex and that it modulates antioxidant and detoxification programs by acting via the ARE.

Preeclamptic plasma induces transcription modifications involving the AP-1 transcriptional regulator JDP2 in endothelial cells

Preeclampsia is a pregnancy disorder characterized by hypertension and proteinuria. In preeclampsia, the placenta releases factors into the maternal circulation that cause a systemic endothelial dysfunction. Herein, we investigated the effects of plasma from women with preeclamptic and normal pregnancies on the transcriptome of an immortalized human umbilical vein endothelial cell line. The cells were exposed for 24 hours to preeclamptic or normal pregnancy plasma and their transcriptome was analyzed using Agilent microarrays. A total of 116 genes were found differentially expressed: 71 were up-regulated and 45 were down-regulated. In silico analysis revealed significant consistency and identified four functional categories of genes: mitosis and cell cycle progression, anti-apoptotic, fatty acid biosynthesis, and endoplasmic reticulum stress effectors. Moreover, several genes involved in vasoregulation and endothelial homeostasis showed modified expression, including EDN1, APLN, NOX4, and CBS. Promoter analysis detected, among the up-regulated genes, a significant overrepresentation of genes containing activation protein-1 regulatory sites. This correlated with down-regulation of JDP2, a gene encoding a repressor of activation protein-1. The role of JDP2 in the regulation of a subset of genes in the human umbilical vein endothelial cells was confirmed by siRNA inhibition. We characterized transcriptional changes induced by preeclamptic plasma on human umbilical vein endothelial cells, and identified, for the first time to our knowledge, JDP2 as a regulator of a subset of genes modified by preeclamptic plasma.

Control of Oxidative Stress and Generation of Induced Pluripotent Stem Cell-like Cells by Jun Dimerization Protein 2

We report here that the Jun dimerization protein 2 (JDP2) plays a critical role as a cofactor for the transcription factors nuclear factor-erythroid 2-related factor 2 (Nrf2) and MafK in the regulation of the antioxidants and production of reactive oxygen species (ROS). JDP2 associates with Nrf2 and MafK (Nrf2-MafK) to increase the transcription of antioxidant response element-dependent genes. Oxidative-stress-inducing reagent led to an increase in the intracellular accumulation of ROS and cell proliferation in Jdp2 knock-out mouse embryonic fibroblasts. In Jdp2-Cre mice mated with reporter mice, the expression of JDP2 was restricted to granule cells in the brain cerebellum. The induced pluripotent stem cells (iPSC)-like cells were generated from DAOY medulloblastoma cell by introduction of JDP2, and the defined factor OCT4. iPSC-like cells expressed stem cell-like characteristics including alkaline phosphatase activity and some stem cell markers. However, such iPSC-like cells also proliferated rapidly, became neoplastic, and potentiated cell malignancy at a later stage in SCID mice. This study suggests that medulloblastoma cells can be reprogrammed successfully by JDP2 and OCT4 to become iPSC-like cells. These cells will be helpful for studying the generation of cancer stem cells and ROS homeostasis.

Comparison of genome-wide binding of MyoD in normal human myogenic cells and rhabdomyosarcomas identifies regional and local suppression of promyogenic transcription factors

Rhabdomyosarcoma is a pediatric tumor of skeletal muscle that expresses the myogenic basic helix-loop-helix protein MyoD but fails to undergo terminal differentiation. Prior work has determined that DNA binding by MyoD occurs in the tumor cells, but myogenic targets fail to activate. Using MyoD chromatin immunoprecipitation coupled to high-throughput sequencing and gene expression analysis in both primary human muscle cells and RD rhabdomyosarcoma cells, we demonstrate that MyoD binds in a similar genome-wide pattern in both tumor and normal cells but binds poorly at a subset of myogenic genes that fail to activate in the tumor cells. Binding differences are found both across genomic regions and locally at specific sites that are associated with binding motifs for RUNX1, MEF2C, JDP2, and NFIC. These factors are expressed at lower levels in RD cells than muscle cells and rescue myogenesis when expressed in RD cells. MEF2C is located in a genomic region that exhibits poor MyoD binding in RD cells, whereas JDP2 exhibits local DNA hypermethylation in its promoter in both RD cells and primary tumor samples. These results demonstrate that regional and local silencing of differentiation factors contributes to the differentiation defect in rhabdomyosarcomas.

The transcription factor Jdp2 controls bone homeostasis and antibacterial immunity by regulating osteoclast and neutrophil differentiation

Jdp2 is an AP-1 family transcription factor that regulates the epigenetic status of histones. Previous in vitro studies revealed that Jdp2 is involved in osteoclastogenesis. However, the roles of Jdp2 in vivo and its pleiotropic functions are largely unknown. Here we generated Jdp2(-/-) mice and discovered its crucial roles not only in bone metabolism but also in differentiation of neutrophils. Jdp2(-/-) mice exhibited osteopetrosis resulting from impaired osteoclastogenesis. Jdp2(-/-) neutrophils were morphologically normal but had impaired surface expression of Ly6G, bactericidal function, and apoptosis. We also found that ATF3 was an inhibitor of neutrophil differentiation and that Jdp2 directly suppresses its expression via inhibition of histone acetylation. Strikingly, Jdp2(-/-) mice were highly susceptible to Staphylococcus aureus and Candida albicans infection. Thus, Jdp2 plays pivotal roles in in vivo bone homeostasis and host defense by regulating osteoclast and neutrophil differentiation.

The bZIP repressor proteins, c-Jun dimerization protein 2 and activating transcription factor 3, recruit multiple HDAC members to the ATF3 promoter

JDP2, is a basic leucine zipper (bZIP) protein displaying a high degree of homology with the stress inducible transcription factor, ATF3. Both proteins bind to cAMP and TPA response elements and repress transcription by multiple mechanisms. Histone deacetylases (HDACs) play a key role in gene inactivation by deacetylating lysine residues on histones. Here we describe the association of JDP2 and ATF3 with HDACs 1, 2-6 and 10. Association of HDAC3 and HDAC6 with JDP2 and ATF3 occurs via direct protein-protein interactions. Only part of the N-terminal bZIP motif of JDP2 and ATF3 basic domain is necessary and sufficient for the interaction with HDACs in a manner that is independent of coiled-coil dimerization. Class I HDACs associate with the bZIP repressors via the DAC conserved domain whereas the Class IIb HDAC6 associates through its C-terminal unique binder of ubiquitin Zn finger domain. Both JDP2 and ATF3 are known to bind and repress the ATF3 promoter. MEF cells treated with histone deacetylase inhibitor, trichostatin A (TSA) display enhanced ATF3 transcription. ATF3 enhanced transcription is significantly reduced in MEF cells lacking both ATF3 and JDP2. Collectively, we propose that the recruitment of multiple HDAC members to JDP2 and ATF3 is part of their transcription repression mechanism.

An introduction to murine models of atrial fibrillation

Understanding the mechanism of re-entrant arrhythmias in the past 30 years has allowed the development of almost curative therapies for many rhythm disturbances. The complex, polymorphic arrhythmias of atrial fibrillation (AF) and sudden death are, unfortunately, not yet well understood, and hence still in need of adequate therapy. AF contributes markedly to morbidity and mortality in aging Western populations. In the past decade, many genetically altered murine models have been described and characterized. Here, we review genetically altered murine models of AF; powerful tools that will enable a better understanding of the mechanisms of AF and the assessment of novel therapeutic interventions.

The transcription factor network associated with the amino acid response in mammalian cells

Mammals exhibit multiple adaptive mechanisms that sense and respond to fluctuations in dietary nutrients. Consumption of reduced total dietary protein or a protein diet that is deficient in 1 or more of the essential amino acids triggers wide-ranging changes in feeding behavior and gene expression. At the level of individual cells, dietary protein deficiency is manifested as amino acid (AA) deprivation, which activates the AA response (AAR). The AAR is composed of a collection of signal transduction pathways that terminate in specific transcriptional programs designed to catalyze adaptation to the nutrient stress or, ultimately, undergo apoptosis. Independently of the AAR, endoplasmic reticulum stress activates 3 signaling pathways, collectively referred to as the unfolded protein response. The transcription factor activating transcription factor 4 is one of the terminal transcriptional mediators for both the AAR and the unfolded protein response, leading to a significant degree of overlap with regard to the target genes for these stress pathways. Over the past 5 y, research has revealed that the basic leucine zipper superfamily of transcription factors plays the central role in the AAR. Formation of both homo- and heterodimers among the activating transcription factor, CCAAT enhancer-binding protein, and FOS/JUN families of basic leucine zipper proteins forms the nucleus of a highly integrated transcription factor network that determines the initiation, magnitude, and duration of the cellular response to dietary protein or AA limitation.

JDP2 inhibits the epithelial-to-mesenchymal transition in pancreatic cancer BxPC3 cells

Pancreatic carcinoma is one of the most malignant and aggressive cancers. Increased motility and invasiveness of pancreatic cancer cells are believed to be associated with epithelial-to-mesenchymal transition (EMT). However, the molecular basis of EMT in pancreatic cancer cells is poorly understood. In this study, we examined the relationship between Jun dimerization protein 2 (JDP2), which is an AP-1 inhibitor, and EMT in human pancreatic carcinoma cells. We demonstrated that transforming growth factor-β1 (TGF-β1) promoted epidermal growth factor (EGF)-induced EMT in co-treated human pancreatic BxPC3 cells and that JDP2 overexpression reversed the EMT that was induced by co-treatment with TGF-β1 and EGF. These results suggest that EGF plays a principal role in EMT through its association with TGF-β1 in human pancreatic BxPC3 cells and that JDP2 may be a molecular target for pancreatic carcinoma intervention.

Overexpression of cAMP-response element modulator causes abnormal growth and development of the atrial myocardium resulting in a substrate for sustained atrial fibrillation in mice

BACKGROUND AND METHODS

Atrial fibrillation (AF) is the most common cardiac arrhythmia in clinical practice. The substrate of AF is composed of a complex interplay between structural and functional changes of the atrial myocardium often preceding the occurrence of persistent AF. However, there are only few animal models reproducing the slow progression of the AF substrate to the spontaneous occurrence of the arrhythmia. Transgenic mice (TG) with cardiomyocyte-directed expression of CREM-IbΔC-X, an isoform of transcription factor CREM, develop atrial dilatation and spontaneous-onset AF. Here we tested the hypothesis that TG mice develop an arrhythmogenic substrate preceding AF using physiological and biochemical techniques.

RESULTS

Overexpression of CREM-IbΔC-X in young TG mice (<8weeks) led to atrial dilatation combined with distension of myocardium, elongated myocytes, little fibrosis, down-regulation of connexin 40, loss of excitability with a number of depolarized myocytes, atrial ectopies and inducibility of AF. These abnormalities continuously progressed with age resulting in interatrial conduction block, increased atrial conduction heterogeneity, leaky sarcoplasmic reticulum calcium stores and the spontaneous occurrence of paroxysmal and later persistent AF. This distinct atrial remodelling was associated with a pattern of non-regulated and up-regulated marker genes of myocardial hypertrophy and fibrosis.

CONCLUSIONS

Expression of CREM-IbΔC-X in TG hearts evokes abnormal growth and development of the atria preceding conduction abnormalities and altered calcium homeostasis and the development of spontaneous and persistent AF. We conclude that transcription factor CREM is an important regulator of atrial growth implicated in the development of an arrhythmogenic substrate in TG mice.

JDP2 suppresses transforming growth factor-β1-induced epithelial-mesenchymal transition in human pancreatic cancer cell line Panc-1

AIM: To determine the correlation between overexpression of Jun dimerization protein 2 (JDP2) and epithelial-mesenchymal transition (EMT) in human pancreatic cancer cell line Panc-1.

METHODS: Panc-1 cells were divided into three groups: negative control group, JDP2-transfected group, and empty vector-transfected group. The JDP2-transfected group and empty vector-transfected group were transiently transfected with PCEFL-HA-JDP2 vector and pCEFL vector, respectively. Untreated Panc-1 cells were used as normal controls. Forty-eight hours after transfection, cells were treated with TGF-β1 (10 ng/mL). Cell morphological alternations were examined by phase-contrast microscopy. The expression of mesenchymal marker vimentin and epithelial marker E-cadherin was detected by RT-PCR and Western blot. Cell migration was determined by Transwell motility assay.

RESULTS: TGF-β1-induced EMT was inhibited in the JDP2-transfected group. Compare to the negative control group, cells in the JDP2-transfected group showed no fibroblastic morphology and no significant changes in the levels of E-cadherin and vimentin and in migration ability (48.0 ± 5.3 vs 52.0 ± 7.2). However, cells in the vector-transfected group showed loss of cell-cell contacts, fibroblastic morphology, decreased expression of E-cadherin (mRNA: P < 0.01; protein: P < 0.05), increased expression of vimentin (P < 0.01) and migration ability (48.0 ± 5.3 vs 81.0 ± 10.7, P < 0.01) when compared to the negative control group.

CONCLUSION: JDP2 can inhibit TGF-β1-induced EMT in Panc-1 cells and may be a molecular target for pancreatic carcinoma therapy.

Binding-folding induced regulation of AF1 transactivation domain of the glucocorticoid receptor by a cofactor that binds to its DNA binding domain

Intrinsically disordered (ID) regions of proteins commonly exist within transcription factors, including the N-terminal domain (NTD) of steroid hormone receptors (SHRs) that possesses a powerful activation function, AF1 region. The mechanisms by which SHRs pass signals from a steroid hormone to control gene expression remain a central unresolved problem. The role of N-terminal activation function AF1, which exists in an intrinsically disordered (ID) conformation, in this process is of immense importance. It is hypothesized that under physiological conditions, ID AF1 undergoes disorder/order transition via inter- and intra-molecular communications, which allows AF1 surfaces to interact with specific co-regulatory proteins, critical for the final outcome of target gene expression regulated by SHRs. However, the means by which AF1 acquires functionally folded conformations is not well understood. In this study, we tested whether binding of jun dimerization protein 2 (JDP2) within the DNA binding domain (DBD) of the glucocorticoid receptor (GR) leads to acquisition of functionally active structure in its AF1/NTD. Our results show that signals mediated from GR DBD:JDP2 interactions in a two domain GR fragment, consisting of the entire NTD and little beyond DBD, significantly increased secondary/tertiary structure formation in the NTD/AF1. This increased structure formation facilitated AF1's interaction with specific co-regulatory proteins and subsequent glucocorticoid response element-mediated AF1 promoter:reporter activity. These results support the hypothesis that inter- and intra-molecular signals give a functionally active structure(s) to the GR AF1, which is important for its transcriptional activity.

Lactobacilli and bifidobacteria induce differential interferon-β profiles in dendritic cells

The health promoting effects of probiotics are well-documented; however, current knowledge on immunostimulatory effects is based on data from a single strain or a limited selection of strains or species. Here, we compared the capacity of 27 lactobacilli and 16 bifidobacteria strains to stimulate bone marrow-derived dendritic cells (DC). Most lactobacilli strains, including Lactobacillus acidophilus, Lactobacillus gasseri, Lactobacillus casei and Lactobacillus plantarum, induced strong IL-12 and TNF-α production and up-regulation of maturation markers. In contrast, all bifidobacteria and certain lactobacilli strains were low IL-12 and TNF-α inducers. IL-10 and IL-6 levels showed less variation and no correlation with IL-12 and TNF-α. DC matured by strong IL-12-inducing strains also produced high levels of interferon (IFN)-β. When combining two strains, low IL-12 inducers inhibited this IFN-β production as well as IL-12 and Th1-skewing chemokines. The IFN-β induction was mediated through c-Jun N-terminal kinase (JNK) irrespective of the stimulating strain. The inhibitory bacteria induced higher levels of the transcription factor c-Jun dimerization protein (JDP)-2, thereby counteracting the effect of JNK. Our data demonstrate that lactobacilli can be divided into two groups of bacteria featuring contrasting effects, while all bifidobacteria exhibit uniform effects. This underlines the importance of selecting the proper strain(s) for probiotic purposes.

Phosphorylation of JDP2 on threonine-148 by the c-Jun N-terminal kinase targets it for proteosomal degradation

JDP2 (c-Jun dimerization protein 2) is a member of the basic leucine zipper family of transcription factors that is ubiquitously expressed in all examined cell types. JDP2 is phosphorylated on Thr148 by JNK (c-Jun N-terminal kinase) and p38 kinase, although the functional role of its phosphorylation is unknown. In the present paper we show that the JDP2 protein level is dramatically reduced in response to serum stimulation, anisomycin treatment, ultraviolet light irradiation and cycloheximide treatment, all of which activate the JNK pathway. In addition, endogenous and overexpressed JDP2 are phosphorylated in response to these stimuli. Replacement of Thr148 with an alanine residue stabilizes ectopically expressed JDP2 in the presence of the stimuli; conversely, substitution with glutamic acid destabilizes it. Serum-induced phosphorylation and degradation of JDP2 are specific to JNK activation since a JNK inhibitor (SP600125) abolishes these effects, whereas p38 and MEK inhibitors (SB203580 and UO126) have no effect. In the presence of cycloheximide, JDP2 is rapidly phosphorylated and degraded due to the combined effects of protein synthesis inhibition and activation of JNK. Pre-treatment of cells with SP600125 prior to cycloheximide treatment significantly prolongs the half-life of JDP2 that is found mainly in the unphosphorylated form. Lastly, the proteasome inhibitor (MG132) rescues JDP2 degradation following cycloheximide treatment and increases the expression of the JDP2 phospho-mimetic T148E mutant. Collectively, these results suggest that phosphorylation of JDP2 on thr148 by JNK targets it to the proteasome for degradation.

Involvement of Jun dimerization protein 2 (JDP2) in the maintenance of Epstein-Barr virus latency

Reactivation of the Epstein-Barr virus from latency is dependent on expression of the BZLF1 viral immediate-early protein. The BZLF1 promoter (Zp) normally exhibits only low basal activity but is activated in response to chemical inducers such as 12-O-tetradecanoylphorbol-13-acetate and calcium ionophore. We found that Jun dimerization protein 2 (JDP2) plays a significant role in suppressing Zp activity. Reporter, EMSA, and ChIP assays of a Zp mutant virus revealed JDP2 association with Zp at the ZII cis-element, a binding site for CREB/ATF/AP-1. Suppression of Zp activity by JDP2 correlated with HDAC3 association and reduced levels of histone acetylation. Although introduction of point mutations into the ZII element of the viral genome did not increase the level of BZLF1 production, silencing of endogenous JDP2 gene expression by RNA interference increased the levels of viral early gene products and viral DNA replication. These results indicate that JDP2 plays a role as a repressor of Zp and that its replacement by CREB/ATF/AP-1 at ZII is crucial to triggering reactivation from latency to lytic replication.

Angiotensin II signaling up-regulates the immediate early transcription factor ATF3 in the left but not the right atrium

The atria respond to various pathological stimuli including pressure and volume overload with remodeling and dilatation. Dilatation of the left atrium is associated with atrial fibrillation. The mechanisms involved in chamber-specific hypertrophy are largely unknown. Angiotensin II is hypothesized to take part in mediating this response. ATF3 is an immediate early gene found at the receiving end of multiple stress and growth stimuli. Here we characterize ATF3 as a direct target gene for angiotensin II. ATF3 expression is regulated by angiotensin receptor-mediated signaling in vivo and in vitro at the transcriptional level. ATF3 induction is mediated by cooperation between both the AT(1A) and AT₂ receptor subtypes. While AT₂R blocker (PD123319) efficiently blocks ATF3 induction in response to angiotensin II injection, it results in an increase in blood pressure indicating that the effect of angiotensin II on ATF3 is independent of its effect on blood pressure. In contrast to adrenergic stimulation that induces ATF3 in all heart chambers, ATF3 induction in response to angiotensin II occurs primarily in the left chambers. We hypothesize that the activation of differential signaling pathways accounts for the chamber-specific induction of ATF3 expression in response to angiotensin II stimulation. Angiotensin II injection rapidly activates the EGFR-dependent pathways including ERK and PI3K-AKT in the left but not the right atrium. EGF receptor inhibitor (Gefitinib/Iressa) as well as the AKT inhibitor (Triciribine) significantly abrogates ATF3 induction by angiotensin II in the left chambers. Collectively, our data strongly place ATF3 as a unique nuclear protein target in response to angiotensin II stimulation in the atria. The spatial expression of ATF3 may add to the understanding of the signaling pathways involved in cardiac response to neuro-hormonal stimulation, and in particular to the understanding of left atrial-generated pathology such as atrial fibrillation.

Jun dimerization protein 2 controls senescence and differentiation via regulating histone modification

Transcription factor, Jun dimerization protein 2 (JDP2), binds directly to histones and DNAs and then inhibits the p300-mediated acetylation both of core histones and of reconstituted nucleosomes that contain JDP2 recognition DNA sequences. JDP2 plays a key role as a repressor of adipocyte differentiation by regulation of the expression of the gene C/EBPδ via inhibition of histone acetylation. Moreover, JDP2-deficient mouse embryonic fibroblasts (JDP2^−/− MEFs) are resistant to replicative senescence. JDP2 inhibits the recruitment of polycomb repressive complexes (PRC1 and PRC2) to the promoter of the gene encoding p16^Ink4a, resulting from the inhibition of methylation of lysine 27 of histone H3 (H3K27). Therefore, it seems that chromatin-remodeling factors, including the PRC complex controlled by JDP2, may be important players in the senescence program. The novel mechanisms that underline the action of JDP2 in inducing cellular senescence and suppressing adipocyte differentiation are reviewed.

Histone chaperone Jun dimerization protein 2 (JDP2): role in cellular senescence and aging

Transcription factor Jun dimerization protein 2 (JDP2) binds directly to histones and DNA, and inhibits p300-mediated acetylation of core histones and reconstituted nucleosomes that contain JDP2-recognition DNA sequences. The region of JDP2 that encompasses its histone-binding domain and DNA-binding region is essential to inhibit histone acetylation by histone acetyltransferases. Moreover, assays of nucleosome assembly in vitro demonstrate that JDP2 also has histone-chaperone activity. The mutation of the region responsible for inhibition of histone acetyltransferase activity within JDP2 eliminates repression of transcription from the c-jun promoter by JDP2, as well as JDP2-mediated inhibition of retinoic-acid-induced differentiation. Thus JDP2 plays a key role as a repressor of cell differentiation by regulating the expression of genes with an activator protein 1 (AP-1) site via inhibition of histone acetylation and/or assembly and disassembly of nucleosomes. Senescent cells show a series of alterations, including flatten and enlarged morphology, increase in nonspecific acidic β-galactosidase activity, chromatin condensation, and changes in gene expression patterns. The onset and maintenance of senescence are regulated by two tumor suppressors, p53 and retinoblastoma proteins. The expression of p53 and retinoblastoma proteins is regulated by two distinct proteins, p16(Ink4a) and Arf, respectively, which are encoded by cdkn2a. JDP2 inhibits recruitment of the polycomb repressive complexes 1 and 2 (PRC-1 and PRC-2) to the promoter of the gene that encodes p16(Ink4a) and inhibits the methylation of lysine 27 of histone H3 (H3K27). The PRCs associate with the p16(Ink4a)/Arf locus in young proliferating cells and dissociate from it in senescent cells. Therefore, it seems that chromatin-remodeling factors that regulate association and dissociation of PRCs, and are controlled by JDP2, might play an important role in the senescence program. The molecular mechanisms that underlie the action of JDP2 in cellular aging and replicative senescence by mediating the dissociation of PRCs from the p16(Ink4a)/Arf locus are discussed.

Suppression of cell-cycle progression by Jun dimerization protein-2 (JDP2) involves downregulation of cyclin-A2

We report here a novel role for Jun dimerization protein-2 (JDP2) as a regulator of the progression of normal cells through the cell cycle. To determine the role of JDP2 in vivo, we generated Jdp2-knockout (Jdp2KO) mice by targeting exon-1 to disrupt the site of initiation of transcription. The epidermal thickening of skin from the Jdp2KO mice after treatment with 12-O-tetradecanoylphorbol 13-acetate (TPA) proceeded more rapidly than that of control mice, and more proliferating cells were found at the epidermis. Fibroblasts derived from embryos of Jdp2KO mice proliferated faster and formed more colonies than fibroblasts from wild-type mice. JDP2 was recruited to the promoter of the gene for cyclin-A2 (ccna2) at the AP-1 site. Cells lacking Jdp2 had elevated levels of cyclin-A2 mRNA. Furthermore, reintroduction of JDP2 resulted in the repression of transcription of ccna2 and of cell-cycle progression. Thus, transcription of the gene for cyclin-A2 appears to be a direct target of JDP2 in the suppression of cell proliferation.

Bifidobacterium bifidum actively changes the gene expression profile induced by Lactobacillus acidophilus in murine dendritic cells

Dendritic cells (DC) play a pivotal regulatory role in activation of both the innate as well as the adaptive immune system by responding to environmental microorganisms. We have previously shown that Lactobacillus acidophilus induces a strong production of the pro-inflammatory and Th1 polarizing cytokine IL-12 in DC, whereas bifidobacteria do not induce IL-12 but inhibit the IL-12 production induced by lactobacilli. In the present study, genome-wide microarrays were used to investigate the gene expression pattern of murine DC stimulated with Lactobacillus acidophilus NCFM and Bifidobacterium bifidum Z9. L. acidophilus NCFM strongly induced expression of interferon (IFN)-β, other virus defence genes, and cytokine and chemokine genes related to the innate and the adaptive immune response. By contrast, B. bifidum Z9 up-regulated genes encoding cytokines and chemokines related to the innate immune response. Moreover, B. bifidum Z9 inhibited the expression of the Th1-promoting genes induced by L. acidophilus NCFM and had an additive effect on genes of the innate immune response and Th2 skewing genes. The gene encoding Jun dimerization protein 2 (JDP2), a transcription factor regulating the activation of JNK, was one of the few genes only induced by B. bifidum Z9. Neutralization of IFN-β abrogated L. acidophilus NCFM-induced expression of Th1-skewing genes, and blocking of the JNK pathway completely inhibited the expression of IFN-β. Our results indicate that B. bifidum Z9 actively inhibits the expression of genes related to the adaptive immune system in murine dendritic cells and that JPD2 via blocking of IFN-β plays a central role in this regulatory mechanism.

Epigenetic regulation of p16Ink4a and Arf by JDP2 in cellular senescence

In response to accumulating cellular stress, cells protect themselves from abnormal growth by entering the senescent stage. Senescence is controlled mainly by gene products from the p16Ink4a/Arf locus. In mouse cells, the expression of p16Ink4a and Arf increases continuously during proliferation in cell culture. Transcription from the locus is under complex control. p16Ink4a and Arf respond independently to positive and negative signals, and the entire locus is epigenetically suppressed by histone methylation that depends on the Polycomb repressive complex-1 and -2 (PRC1 and PRC2). In fact, the PRCs associate with the p16Ink4a/Arf locus in young proliferating cells and dissociate in aged senescent cells. Thus, it seems that chromatin-remodeling factors that regulate association and dissociation of PRCs might be important players in the senescence program. Here, we summarize the molecular mechanisms that mediate cellular aging and introduce the Jun dimerization protein 2 (JDP2) as a factor that regulates replicative senescence by mediating dissociation of PRCs from the p16Ink4a/Arf locus.

The AP-1 repressor protein, JDP2, potentiates hepatocellular carcinoma in mice

Background

The AP-1 transcription factor plays a major role in cell proliferation, apoptosis, differentiation and developmental processes. AP-1 proteins are primarily considered to be oncogenic. Gene disruption studies placed c-Jun as an oncogene at the early stage of a mouse model of hepatocellular carcinoma. Mice lacking c-Jun display reduced number and size of hepatic tumors attributed to elevated p53 expression and increased apoptosis. This suggests that c-Jun inhibition may serve as a therapeutic target for liver cancer. The c-Jun dimerization protein 2, JDP2 is an AP-1 repressor protein that potently inhibits AP-1 transcription. On the other hand, the JDP2 locus was found at a recurring viral integration site in T-cell lymphoma. We sought to examine the potential of JDP2 to inhibit c-Jun/AP-1 oncogenic activity in mice. Towards this end, we generated a tetracycline inducible transgenic mouse expressing JDP2 specifically in the liver. We used diethylnitrosamine (DEN) injection to initiate liver cancer in mice and assessed the extent of liver cancer in JDP2-transgenic and wild type control mice by biochemical and molecular biology techniques.

Results

JDP2-transgenic mice display normal liver function. JDP2-transgenic mice displayed potentiation of liver cancer, higher mortality and increased number and size of tumors. The expression of JDP2 at the promotion stage was found to be the most critical for enhancing liver cancer severity.

Conclusions

This study suggests that JDP2 expression may play a critical role in liver cancer development by potentiating the compensatory proliferative response and increased inflammation in the DEN liver cancer model.

Relationship of JDP2 with invasion and metastasis of pancreatic cancer

AIM: To investigate the expression and the clinical pathological significance of JDP2 protein in pancreatic cancer.

METHODS: The expression of JDP2 protein in 36 pancreatic cancer tissues and matched non-cancerous adjacent tissues were detected by Western blot. The association between the expression of JDP2 protein and the prognosis of patients were analyzed by Log-rank test.

RESULTS: The expression of JDP2 protein significantly decreased in pancreatic cancer compared with the matched non-cancerous adjacent tissues (0.287 ± 0.052 vs 0.517 ± 0.172, P < 0.05). The expression of JDP2 protein was closely associated with tumor size, histological type, invasion degree, lymph node metastasis, distant metastasis and clinical stage (P < 0.05). The survival time of the patients with low JDP2 expression significantly shortened (P < 0.01).

CONCLUSION: JDP2 may be closely associated with the proliferation, invasion, metastasis and prognosis of pancreatic cancer.

Activation of alternative Jdp2 promoters and functional protein isoforms in T-cell lymphomas by retroviral insertion mutagenesis

Retroviral insertional mutagenesis has been instrumental for the identification of genes important in cancer development. The molecular mechanisms involved in retroviral-mediated activation of proto-oncogenes influence the distribution of insertions within specific regions during tumorigenesis and hence may point to novel gene structures. From a retroviral tagging screen on tumors of 1767 SL3-3 MLV-infected BALB/c mice, intron 2 of the AP-1 repressor Jdp2 locus was found frequently targeted by proviruses resulting in upregulation of non-canonical RNA subspecies. We identified several promoter regions within 1000 bp upstream of exon 3 that allowed for the production of Jdp2 protein isoforms lacking the histone acetylase inhibitory domain INHAT present in canonical Jdp2. The novel Jdp2 isoforms localized to the nucleus and over-expression in murine fibroblast cells induced cell death similar to canonic Jdp2. When expressed in the context of oncogenic NRAS both full length Jdp2 and the shorter isoforms increased anchorage-independent growth. Our results demonstrate a biological function of Jdp2 lacking the INHAT domain and suggest a post-genomic application for the use of retroviral tagging data in identifying new gene products with a potential role in tumorigenesis.

JDP2 (Jun Dimerization Protein 2)-deficient mouse embryonic fibroblasts are resistant to replicative senescence

JDP2 (Jun dimerization protein 2, an AP-1 transcription factor) is involved in the regulation of the differentiation and proliferation of cells. We report here that JDP2-deficient mouse embryonic fibroblasts (Jdp2(-/-) MEF) are resistant to replicative senescence. In the absence of JDP2, the level of expression of p16(Ink4a), which is known to rise as normal fibroblasts age, fell significantly when cells were cultured for more than 2 months. Conversely, the overexpression of JDP2 induced the expression of genes for p16(Ink4a) and p19(Arf). Moreover, at the promoter of the gene for p16(Ink4a) in Jdp2(-/-) MEF, the extent of methylation of lysine 27 of histone H3 (H3K27), which is important for gene silencing, increased. Polycomb-repressive complexes (PRC-1 and PRC-2), which are responsible for histone methylation, bound efficiently to the promoter to repress the expression of the gene for p16(Ink4a). As a result, JDP2-deficient MEF became resistant to replicative senescence. Our results indicate that JDP2 is involved in the signaling pathway for senescence via epigenetic regulation of the expression of the gene for p16(Ink4a).

The ubiquitously expressed bZIP inhibitor, JDP2, suppresses the transcription of its homologue immediate early gene counterpart, ATF3

JDP2 is a ubiquitously expressed bZIP repressor protein. JDP2 binds TPA response element and cyclic AMP response element located within various promoters. JDP2 displays a high degree of homology to the immediate early gene ATF3. ATF3 plays a crucial role in the cellular adaptive response to multiple stress insults as well as growth stimuli. We have identified ATF3 as a potential target gene for JDP2 repression. JDP2 regulates the ATF3 promoter potentially through binding to both the consensus ATF/CRE site and a non-consensus ATF3 auto-repression DNA-binding element. Expression of ATF3 protein in wild-type mouse embryo fibroblast (MEF) cells is below the detectable levels, whereas, JDP2 disrupted MEF cells display noticeable level of ATF3 protein. Following either serum or ER stress stimulation, ATF3 expression is potentiated in JDP2-KO fibroblast cells as compared with wild-type cells. Mice with either JDP2 over-expression or JDP2 disruption display undetectable level of ATF3 protein. However, ATF3 induction in response to either growth or stress signals is dependent on JDP2 expression level. ATF3 induction is attenuated in JDP2 over-expressing mice whereas is potentiated in JDP2-KO mice as compared with the corresponding wild-type mice. Collectively, the data presented strongly suggest that JDP2 plays a role in the determination of the ATF3 adaptive cellular threshold response to different stress insults and growth stimuli.

PCTA: a new player in TGF-beta signaling

Transforming growth factor beta (TGF-beta) regulates a wide variety of biological activities by binding to cell surface serine/threonine kinase receptors. Canonical TGF-beta signaling is mediated by Smad proteins, which transduce the TGF-beta signal from the cell surface into the nucleus to regulate transcription. Upon TGF-beta binding and receptor activation, the TGF-beta receptor phosphorylates Smad2 and Smad3. SARA (Smad anchor for receptor activation) and cPML (cytoplasmic promyelocytic leukemia protein) recruit Smad2 and Smad3 for phosphorylation by the TGF-beta receptor. cPML is sequestered in the nucleus by the homeodomain protein TGIF (TG-interacting factor), a negative regulator of TGF-beta signaling. Recently, PCTA (PML competitor for TGIF association) has been shown to compete with cPML for binding to TGIF, resulting in the accumulation of cPML in the cytoplasm, where it mediates the interaction between Smad2/3 and SARA and coordinates the phosphorylation of Smad2 and Smad3 by the TGF-beta receptor. Accordingly, PCTA promotes TGF-beta-mediated transcriptional regulation and growth inhibition. Thus, PCTA defines a new regulator in TGF-beta signaling.

IRF2-binding protein-1 is a JDP2 ubiquitin ligase and an inhibitor of ATF2-dependent transcription

Jun-dimerization protein 2 (JDP2) is a member of the activating protein-1 (AP-1) family of transcription factors. JDP2 dimerizes with other AP-1 proteins such as activating transcription factor-2 (ATF2) and Jun to repress transcription from promoters that contain a cyclic AMP-responsive element (CRE). Interferon regulatory factor-2-binding protein-1 (IRF2-BP1), which is reported to be a transcriptional corepressor of IRF2, was isolated as a JDP2-binding protein using an epitope-tagging method. As anticipated from the presence of a RING-finger domain, IRF2-BP1 enhanced the polyubiquitination of JDP2. Moreover, IRF2-BP1 repressed ATF2-mediated transcriptional activation from a CRE-containing promoter.