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

Opposing effects of KDM6A and JDP2 on glucocorticoid sensitivity in T-ALL

Glucocorticoids (GCs) are the cornerstone of acute lymphoblastic leukemia (ALL) therapy. Although mutations in NR3C1, which encodes the GC receptor (GR), and other genes involved in GC signaling occur at relapse, additional mechanisms of adaptive GC resistance are uncertain. We transplanted and treated 10 primary mouse T-lineage acute lymphoblastic leukemias (T-ALLs) initiated by retroviral insertional mutagenesis with GC dexamethasone (DEX). Multiple distinct relapsed clones from 1 such leukemia (T-ALL 8633) exhibited discrete retroviral integrations that upregulated Jdp2 expression. This leukemia harbored a Kdm6a mutation. In the human T-ALL cell line CCRF-CEM, enforced JDP2 overexpression conferred GC resistance, whereas KDM6A inactivation unexpectedly enhanced GC sensitivity. In the context of KDM6A knockout, JDP2 overexpression induced profound GC resistance, counteracting the sensitization conferred by KDM6A loss. These resistant "double mutant" cells with combined KDM6A loss and JDP2 overexpression exhibited decreased NR3C1 mRNA and GR protein upregulation upon DEX exposure. Analysis of paired samples from 2 patients with KDM6A-mutant T-ALL in a relapsed pediatric ALL cohort revealed a somatic NR3C1 mutation at relapse in 1 patient and a markedly elevated JDP2 expression in the other. Together, these data implicate JDP2 overexpression as a mechanism of adaptive GC resistance in T-ALL, which functionally interacts with KDM6A inactivation.

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 is directly regulated by ATF4 and modulates TRAIL sensitivity by suppressing the ATF4-DR5 axis

Jun dimerization protein 2 (JDP2) is a bZip‐type transcription factor, which acts as a repressor or activator of several cellular processes, including cell differentiation and chromatin remodeling. Previously, we found that a stress‐responsive transcription factor, known as activating transcription factor 4 (ATF4), enhances JDP2 gene expression in human astrocytoma U373MG and cervical cancer HeLa cells; however, the role of JDP2 in the ATF4‐mediated stress response remained unclear. Here, we reported that siRNA‐mediated JDP2 knockdown enhances the expression of several ATF4 target genes, including ASNS, and death receptors 4 and 5 (DR4 and DR5) in HeLa cells. In addition, the results of a transient reporter assay indicate that JDP2 overexpression represses ER stress‐mediated DR5 promoter activation suggesting that JDP2 negatively regulates ATF4‐mediated gene expression. Curiously, knockdown of JDP2 increases the sensitivity of cells to TNF‐related apoptosis‐inducing ligand (TRAIL), which induces apoptosis in cancer cells through DR4 and DR5. These results indicate that JDP2 functions as a negative feedback regulator of the ATF4 pathway and contributes to TRAIL resistance in cancer cells.

Anti-cancer potential of persimmon (Diospyros kaki) leaves via the PDGFR-Rac-JNK pathway

Persimmon leaves are known to have some beneficial effects, including ROS elimination, lipid circulation, and neuronal protection. However, their anti-cancer properties and the underlying mechanisms remain unclear. Herein, we show that treatment with the ethanol extract of persimmon, Diospyros kaki, leaves (EEDK) induces cancer cell death and inhibits cell proliferation. Using fluorescence resonance energy transfer (FRET) technology with genetically-encoded biosensors, we first found that EEDK stimulates a PDGFR-Rac signaling cascade in live cells. Moreover, we found that downstream of the PDGFR-Rac pathway, JNKs are activated by EEDK. In contrast, JNK-downstream inhibitors, such as CoCl2, T-5224, and pepstatin A, attenuated EEDK-induced cell death. Thus, we illustrate that the PDGFR-Rac-JNK signaling axis is triggered by EEDK, leading to cancer cell death, suggesting the extract of persimmon leaves may be a promising anti-cancer agent.

A Forward Genetic Screen Targeting the Endothelium Reveals a Regulatory Role for the Lipid Kinase Pi4ka in Myelo- and Erythropoiesis

Given its role as the source of definitive hematopoietic cells, we sought to determine whether mutations initiated in the hemogenic endothelium would yield hematopoietic abnormalities or malignancies. Here, we find that endothelium-specific transposon mutagenesis in mice promotes hematopoietic pathologies that are both myeloid and lymphoid in nature. Frequently mutated genes included previously recognized cancer drivers and additional candidates, such as Pi4ka, a lipid kinase whose mutation was found to promote myeloid and erythroid dysfunction. Subsequent validation experiments showed that targeted inactivation of the Pi4ka catalytic domain or reduction in mRNA expression inhibited myeloid and erythroid cell differentiation in vitro and promoted anemia in vivo through a mechanism involving deregulation of AKT, MAPK, SRC, and JAK-STAT signaling. Finally, we provide evidence linking PI4KAP2, previously considered a pseudogene, to human myeloid and erythroid leukemia.

miR-501 acts as an independent prognostic factor that promotes the epithelial-mesenchymal transition through targeting JDP2 in hepatocellular carcinoma

Hepatocellular carcinoma (HCC), the second common cancer, was a kind of primary liver cancer with high incidence. miR-501, identified as a novel regulator, was acted as a potential biomarker in several diseases. JDP2, acted as a repressor of AP-1 complex, was a member of the basic leucine zipper (bZIP) transcription factor family. RT-qPCR was applied to evaluate miR-501 and JDP2 expression level and we found that miR-501 was upregulated in HCC tissues and cells. miR-501 ectopic expression promoted HCC cell invasion and epithelial-mesenchymal transition (EMT), while low expression present the opposite results. JDP2 was downregulated in HCC tissues and cells, and overexpressed JDP2 facilitated HCC cell invasion and EMT. Furthermore, luciferase reporter assay indicated that JDP2 was a target of miR-501 and altered miR-501 expression the JPD2 mRNA may changed. The expression of miR-501 and JDP2 had negative connection in HCC tissues. In addition, Kaplan-Meier method revealed that miR-501 upregulation or JDP2 downregulation predicted poor prognosis in HCC patients. miR-501 promoted cell invasion and EMT by regulated JDP2 in hepatocellular carcinoma. The newly identified miR-501/JDP2 axis provides novel insight into the pathogenesis of hepatocellular carcinoma.

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: An oncogenic bZIP transcription factor in T cell acute lymphoblastic leukemia

A substantial subset of patients with T cell acute lymphoblastic leukemia (T-ALL) develops resistance to steroids and succumbs to their disease. JDP2 encodes a bZIP protein that has been implicated as a T-ALL oncogene from insertional mutagenesis studies in mice, but its role in human T-ALL pathogenesis has remained obscure. Here we show that JDP2 is aberrantly expressed in a subset of T-ALL patients and is associated with poor survival. JDP2 is required for T-ALL cell survival, as its depletion by short hairpin RNA knockdown leads to apoptosis. Mechanistically, JDP2 regulates prosurvival signaling through direct transcriptional regulation of MCL1. Furthermore, JDP2 is one of few oncogenes capable of initiating T-ALL in transgenic zebrafish. Notably, thymocytes from rag2:jdp2 transgenic zebrafish express high levels of mcl1 and demonstrate resistance to steroids in vivo. These studies establish JDP2 as a novel oncogene in high-risk T-ALL and implicate overexpression of MCL1 as a mechanism of steroid resistance in JDP2-overexpressing cells.

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.

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.

Deregulated Nras expression in knock-in animals harboring a gammaretroviral long terminal repeat at the Nras/Csde1 locus

To investigate mechanisms and phenotypic effects of insertional mutagenesis by gammaretroviruses, we have developed mouse lines containing a single Akv 1-99 long terminal repeat (LTR) and a floxed PGK/Tn5 neomycin cassette at the Nras proto-oncogene at positions previously identified as viral integration sites in Akv 1-99 induced tumors. The insert did not compromise the embryonic development, however, the cassette had an effect on Nras expression in all tissues analyzed. Cre-mediated excision of the PGK/Tn5 neomycin cassette in two of the lines caused upregulation of Nras. Altogether, the knock-in alleles are characterized by modulation of expression of the target gene from more than ten-fold upregulation to three-fold downregulation and exemplify various mechanisms of deregulation by insertional mutagenesis. LTR knock-in mice may serve as a tool to investigate mechanisms of retroviral insertional mutagenesis and as a way of constitutive or induced modulation of expression of a target gene.

Jdp2 downregulates Trp53 transcription to promote leukaemogenesis in the context of Trp53 heterozygosity

We performed a genetic screen in mice to identify candidate genes that are associated with leukaemogenesis in the context of Trp53 heterozygosity. To do this we generated Trp53 heterozygous mice carrying the T2/Onc transposon and SB11 transposase alleles to allow transposon-mediated insertional mutagenesis to occur. From the resulting leukaemias/lymphomas that developed in these mice, we identified nine loci that are potentially associated with tumour formation in the context of Trp53 heterozygosity, including AB041803 and the Jun dimerization protein 2 (Jdp2). We show that Jdp2 transcriptionally regulates the Trp53 promoter, via an atypical AP-1 site, and that Jdp2 expression negatively regulates Trp53 expression levels. This study is the first to identify a genetic mechanism for tumour formation in the context of Trp53 heterozygosity.

Septin9 is involved in septin filament formation and cellular stability

Septin9 (Sept9) is a member of the filament-forming septin family of structural proteins and is associated with a variety of cancers and with hereditary neuralgic amyotrophy. We have generated mice with constitutive and conditional Sept9 knockout alleles. Homozygous deletion of Sept9 results in embryonic lethality around day 10 of gestation whereas mice homozygous for the conditional allele develop normally. Here we report the consequences of homozygous loss of Sept9 in immortalized murine embryonic fibroblasts. Proliferation rate was not changed but cells without Sept9 had an altered morphology compared to normal cells, particularly under low serum stress. Abnormal, fragmented, and multiple nuclei were more frequent in cells without Sept9. Cell migration, as measured by gap-filling and filter-invasion assays, was impaired, but individual cells did not move less than wild-type cells. Sept9 knockout cells showed a reduced resistance to hypo-osmotic stress. Stress fiber and vinculin staining at focal adhesion points was less prominent. Long septin filaments stained for Sept7 disappeared. Instead, staining was found in short, often curved filaments and rings. Furthermore, Sept7 was no longer localized to the mitotic spindle. Together, these data reveal the importance of Sept9 for septin filament formation and general cell stability.

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.

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.

Antisense transcription in gammaretroviruses as a mechanism of insertional activation of host genes

Transcription of retroviruses is initiated at the U3-R region boundary in the integrated provirus and continues unidirectionally to produce genomic and mRNA products of positive polarity. Several studies have recently demonstrated the existence of naturally occurring protein-encoding transcripts of negative polarity in complex retroviruses. We report here on the identification of transcripts of negative polarity in simple murine leukemia virus (MLV). In T-cell and B-cell lymphomas induced by SL3-3 and Akv MLV, antisense transcripts initiated in the U3 region of the proviral 5' long terminal repeat (LTR) and continued into the cellular proto-oncogenes Jdp2 and Bach2 to create chimeric transcripts consisting of viral and host sequence. The phenomenon was validated in vivo using a knock-in mouse model homozygous for a single LTR at a position known to activate Nras in B-cell lymphomas. A 5' rapid amplification of cDNA ends (RACE) analysis indicated a broad spectrum of initiation sites within the U3 region of the 5' LTR. Our data show for the first time transcriptional activity of negative polarity initiating in the U3 region of simple retroviruses and suggest a novel mechanism of insertional activation of host genes. Elucidation of the nature and potential regulatory role of 5' LTR antisense transcription will be relevant to the design of therapeutic vectors and may contribute to the increasing recognition of pervasive eukaryotic transcription.