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Etoposide is a second-line chemotherapy agent widely used for metastatic colorectal cancer. However, we discovered that etoposide treatment induced greater motility potential in four colorectal cancer cell lines. Therefore, we used microarrays to test the mRNA of these cancer cell lines to investigate the mechanisms of etoposide promoting colorectal cancer metastasis. Differentially expressed genes (DEGs) were identified by comparing the gene expression profiles in samples from etoposide-treated cells and untreated cells in all four colorectal cancer cell lines. Next, these genes went through the Gene Set Enrichment Analysis (GSEA), Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) Pathway analysis. Among the top 10 genes including the upregulated and downregulated, eight genes had close interaction according to the STRING database: FAS, HMMR, JUN, LMNB1, MLL3, PLK2, STAG1 and TBL1X. After etoposide treatment, the cell cycle, metabolism-related and senescence signaling pathways in the colorectal cancer cell lines were significantly downregulated, whereas necroptosis and oncogene pathways were significantly upregulated. We suggest that the differentially expressed genes LMNB1 and JUN are potential targets for predicting colorectal cancer metastasis. These results provide clinical guidance in chemotherapy, and offer direction for further research in the mechanism of colorectal cancer metastasis. [ABSTRACT FROM AUTHOR]

Osteoarthritis (OA) is a chronic degenerative disease characterized by articular cartilage destruction and subchondral bone reconstruction in the early stages. Bergenin (Ber) is a cytoprotective polyphenol found in many medicinal plants. It has been proven to have anti-inflammatory, antioxidant, and other biological activities, which may reveal its potential role in the treatment of OA. This study aimed to determine the potential efficacy of Ber in treating OA and explore the possible underlying mechanism through network pharmacology and validation experiments. The potential co-targets and processes of Ber and OA were predicted by using network pharmacology, including a Venn diagram for intersection targets, a protein‒protein interaction (PPI) network to obtain key potential targets, and GO and KEGG pathway enrichment to reveal the probable mechanism of action of Ber on OA. Subsequently, validation experiments were carried out to investigate the effects and mechanisms of Ber in treating OA in vitro and vivo. Ber suppressed IL-1β-induced chondrocyte apoptosis and extracellular matrix catabolism by inhibiting the STAT3, NF-κB and Jun signalling pathway in vitro. Furthermore, Ber suppressed the expression of osteoclast marker genes and RANKL-induced osteoclastogenesis. Ber alleviated the progression of OA in DMM-induced OA mice model. These results demonstrated the protective efficacy and potential mechanisms of Ber against OA, which suggested that Ber could be adopted as a potential therapeutic agent for treating OA. [ABSTRACT FROM AUTHOR]

Hepatocellular carcinoma, as a common liver cirrhosis complication, has become the sixth most common cancer worldwide, and its increasing incidence has resulted in considerable medical and economic burdens. As a natural polyphenolic compound, kaempferol has exhibits a wide range of antitumor activities against multiple cancer targets. In this study, the Autodock software was used for molecular docking to simulate the interaction process between kaempferol and HCC targets and the PyMOL software was used for visualization. Proliferation of kaempferol HepG2 cells under the effect of kaempferol was detected using Cell Counting Kit-8 (CCK-8) assay, and the apoptosis rate of HepG2 cells was detected using flow cytometry. The expressions of proteins BAX, CDK1, and JUN protein expressions were detected by Western blot. Molecular docking found that the kaempferol ligand has 3 rotatable bonds, 6 nonpolar hydrogen atoms, and 12 aromatic carbon atoms, and can form complexes with the kaempferol targets P53, BAX, AR, CDK1, and JUN through electrostatic energy. GO (Gene Ontology) enrichment analysis suggests that kaempferol regulates the biological function of hepatocellular carcinoma cells and is related to apoptosis. Cell Counting Kit-8 assay suggested that Kaempferol can significantly inhibited HepG2 cell proliferation, and the inhibition rate increased with the increase in drug concentration and incubation time. Moreover, kaempferol can promoted HepG2 cell apoptosis in a dose-dependent manner. This compound upregulated BAX and JUN expression and downregulated CDK1 expression. Thus, Kaempferol can promote HepG2 cell apoptosis, and the regulatory mechanism may be related to the regulation of the expression levels of the apoptosis-related proteins BAX, CDK1, and JUN. [ABSTRACT FROM AUTHOR]

The kinetic patterns of CpG methylation of the cis-regulatory region of heat stress–related genes on exposed to heat stress (at 42 °C) between the Sahiwal and Frieswal cattle was compared in the present study. Using an in vitro whole blood culture model, cells were continuously exposed to heat stress (at 42 °C) for 6 h. Methylation levels of five genes, viz., GPX1, HSP70, HSP90, c-FOS, and JUN were estimated by SyberGreen-based quantitative methylation-specific PCR (qMSP) assay. CpG methylation kinetics at different time points of heat stress (0.5, 1, 2, 4, 6 h) were analyzed using mixed ANOVA. The initial methylation level, estimated at 37 °C, of HSP70 was significantly high in the Sahiwal breed. A significant (p<0.001) time-dependent hypomethylation of an antioxidant gene (GPX1) CpG islands was detected at the acute phase of the stress. Heat shock protein gene (HSP70) showed a similar CpG methylation kinetics where the hypomethylation was prominent from 1 h and persisted up to 4 h. The heat stress responses of both Sahiwal and Frieswal cattle were identical as there was no distinctiveness in the methylation kinetics of CpG islands of studied genes. The acclimatization of Frieswal cattle—a breed developed in India over the years to the tropical climatic conditions, maybe one of the reasons for this similarity. Thus, the present study results could pave a path to understand the molecular mechanism of heat stress and adaptation of indigenous and crossbred cattle populations to the changing scenario in tropical climate conditions. [ABSTRACT FROM AUTHOR]

The sex determination and control of poultry is a key problem in production and scientific research despite few studies on regulatory factors, especially transcription factors in sex determination. In the early stage of this study, high-throughput sequencing was used to screen the differentially expressed gene JUN in male and female embryonic stem cells (ESCs) and primordial germ cells (PGCs). The qRT-PCR discovered that the JUN gene significantly increased from embryonic days (E) 2.5 later in chicken embryo development, and the female gonad expression was much higher than that of the male after E14.5. Lentivirus shRNA-JUN, shRNA-Smad2 interference, and OE-JUN overexpression vectors were successfully constructed. After interfering with JUN in vivo, male characteristics appeared in ZW embryonic gonads at E18.5. Meanwhile, the male-specific genes DMRT1 and Sox9 were upregulated, the female-specific genes FOXL2, ESR1, and CYP19A1 were downregulated, and the estradiol in the gonads was significantly decreased. The situation was reversed after the overexpression of JUN, ZZ chicken embryo developed into female sexual characteristics. The double luciferase report has found that the Smad2 promoter activity was significantly upregulated after interference with JUN, and significantly increased after the deletion of the JUN binding site. After the injection of the Smad2-shRNA vector into the blood vessel in vivo, it was discovered that DMRT1 and Sox9 of ZW embryos at E18.5 were downregulated, FOXL2 and CYP19A1 were significantly upregulated, and the gonads show femininity. In conclusion, this study proves that JUN is a key regulator in the process of chicken female sex differentiation, which can inhibit the transcription of Smad2 and promote the synthesis of estradiol, and participate in the process of chicken sex differentiation. This study lays a foundation for the analysis of the molecular mechanism of chicken sex determination and the development of poultry sex control technology. [ABSTRACT FROM AUTHOR]

Sepsis is a fetal immunological disorder and its complication worsens in the patients with hemodialysis which may increase the risk of death. In the present study, we aimed to investigate the effect of homeodomain-interacting protein kinase 3 (HIPK3) on inflammatory factors and oxidative stress markers in monocytes of rats with sepsis by regulating the c-Jun amino-terminal kinase (JNK)/c-Jun signaling pathway. A rat model of sepsis was initially established using cecal ligation and puncture (CLP) and was further identified by enlarged spleen tissues, inflammation, and oxidative stress. Monocytes were isolated from rats with CLP-induced sepsis. HIPK3 was observed to be downregulated while JUN was upregulated in monocytes from rats with CLP-induced sepsis. Furthermore, isolated monocytes were transduced with lentiviral vectors expressing HIPK3 or shRNA against HIPK3 to explore the effect of HIPK3 on viability and apoptosis of monocytes as well as inflammatory factors and oxidative stress markers. The obtained data exhibited that overexpression of HIPK3 or inhibition of the JNK signaling pathway enhanced proliferation, reduced apoptosis of monocytes, alleviated inflammation, and oxidative stress injury. Consistently, our results may provide evidence that HIPK3 could inhibit the JNK/c-Jun signaling pathway, thereby potentially retarding the progression of sepsis. [ABSTRACT FROM AUTHOR]

The non-virion (NV) protein of viral haemorrhagic septicaemia virus (VHSV), an economically important fish novirhabdovirus, has been implicated in the interference of some host innate mechanisms (i.e. apoptosis) in vitro. This work aimed to characterise the immune-related transcriptome changes in rainbow trout induced by NV protein that have not yet been established in vivo. For that purpose, immune-targeted microarrays were used to analyse the transcriptomes from head kidney and spleen of rainbow trout ( Oncorhynchus mykiss) after injection of recombinant NV (rNV). Results showed the extensive downregulation (and in some cases upregulation) of many innate and adaptive immune response genes not related previously to VHSV infection. The newly identified genes belonged to VHSV-induced genes ( vigs), tumour necrosis factors, Toll-like receptors, antigen processing and presentation, immune co-stimulatory molecules, interleukins, macrophage chemotaxis, transcription factors, etc. Classification of differentially downregulated genes into rainbow trout immune pathways identified stat1 and jun/atf1 transcription factor genes as the most representative of the multipath gene targets of rNV. Altogether, these results contribute to define the role and effects of NV in trout by orchestrating an immunosuppression of the innate immune responses for favouring viral replication upon VHSV infection. Finally, these transcriptome results open up the possibility to find out new strategies against VHSV and better understand the interrelationships between some immune pathways in trout. [ABSTRACT FROM AUTHOR]

In the world, hepatocellular carcinoma (HCC) is one of the most common and most lethal cancers. Currently, standard therapy for unresectable HCC is a local-regional therapy with transarterial chemoembolisation (TACE). In this study, we sought to assess whether plasma circulating microRNAs (miRNAs) can be used to predict the prognosis of HCC patients receiving the TACE treatment. Firstly, we systematically examined TACE therapeutic effectiveness-related circulating miRNAs through miRNA Profiling Chips. As a result, we identified 19 circulating miRNAs to be significantly differentially expressed between the TACE-response group and the TACE-nonresponse group. In the second stage, we performed quantitative analyses of these candidate miRNAs in additional HCC patients treated with TACE and validated two of the aforementioned 19 miRNAs (miR-1285-3p and miR-4741) as candidate biomarkers for predicting prognosis of TACE. Interestingly, we found that miR-1285-3p could directly repress JUN oncogene expression in HCC cells, indicating miR-1285-3p could act as a potential tumor suppressor. In conclusion, our data indicate that circulating miR-1285-3p and miR-4741 was predictive of response to TACE therapy in HCC. [ABSTRACT FROM AUTHOR]

Contamination of cereals with the trichothecene deoxynivalenol (DON) is a global problem in agriculture. DON-related cytotoxicity results from inhibition of translation preceded by a ribotoxic stress response, which is characterized by phosphorylation of the mitogen-activated protein kinases and activation of downstream transcription factors. In this study, we measured the expression of AP-1 associated transcription factor mRNA levels in six human cell lines (Hep-G2, A549, U937, A204, Jurkat, and CaCo-2) by using real-time RT-PCR. Previous work suggested that transcription factors mRNA and protein levels are affected by DON in Hep-G2 cells. In this study, we found significant cell-specific differences in mRNA levels for the transcription factors JUN, JUND, FOS, FOSL2, ATF3, and EGR1. After exposure to 1 µmol/l DON for 3 h, the induction of the transcription factor JUN was highest in the Jurkat (342-fold) and Hep-G2 (84-fold) cell lines. JUND expression was mainly affected in the immunocompetent cell-lines U937 (11-fold) and Jurkat (12-fold), whereas significant FOSL2 induction (5-fold) was only found in Jurkat cells. DON-induced expression of FOS was mainly observed in Hep-G2 (96-fold) and U937 cells (59-fold). In contrast, response of A549 cells to DON was characterized by a distinct induction of ATF3 (44-fold) and EGR1 (92-fold). Time- and concentration-dependent induction of the transcription factors by DON was studied in detail for Hep-G2, A549, A204, and U937 cells. Considering the chronic dietary exposure of humans, broader investigations on DON influence on cell signaling pathways are required to understand the impact of this mycotoxin on human health. [ABSTRACT FROM AUTHOR]

Stabilization of cytoplasmic β-catenin is a hallmark of a variety of cancers. The stabilized β-catenin is able to translocate to the nucleus, where it acts as a transcriptional activator of T-cell factor (TCF)-regulated genes. β-Catenin may cross-talk with many signalling cascades to activate target genes. Whether β-catenin cooperates with AP-1, another transcriptional complex activated during tumorigenesis is not fully clarified. We show that β-catenin co-immunoprecipitates with c-Jun and c-Fos. GST pull-down experiments indicate a physical association of the armadillo repeat domain of β-catenin with the DNA-binding domain of c-Jun and of the C-terminal domain of β-catenin with the N-terminal domain of c-Fos. Promoter studies indicate that overexpression of AP-1 activates the transcription of two β-catenin target genes, cyclin D1 and c-myc, by a mechanism independent of the AP-1 site, and fully dependent on the TCF-binding site. We further demonstrate that AP-1/β-catenin synergism is involved during serum-induced cyclin D1 transcriptional activation. We identify a TCF-binding site on the cyclin D1 promoter which binds in vivo a complex induced by serum, containing β-catenin, TCF4, c-Fos, c-Jun, JunB and JunD. This novel mechanism of interaction between two signalling cascades might contribute to the potentiation of malignancy.Oncogene (2007) 26, 3492–3502. doi:10.1038/sj.onc.1210133; published online 4 December 2006 [ABSTRACT FROM AUTHOR]

Metastasis, the aggressive spread of a malignant tumor to distant organs, is a major cause of death in cancer patients. Despite this critical role in cancer outcomes, the molecular mechanisms that control this process are just beginning to be understood. Metastasis is largely dependent upon the ability of tumor cells to invade the barrier formed by the basement membrane and to migrate through neighboring tissues. This review will summarize the evidence that tumor cell invasion is the result of oncogene-mediated signal transduction pathways that control the expression of a specific set of genes that together mediate tumor cell invasion. We focus on the role of the transcription factor AP-1 to both induce the expression of genes that function as invasion effectors and repress other genes that function as invasion suppressors. This identifies AP-1 as a critical regulator of a complex program of gene expression that defines the invasive phenotype.Oncogene (2007) 26, 1–10. doi:10.1038/sj.onc.1209759; published online 26 June 2006 [ABSTRACT FROM AUTHOR]

The p63α isoforms of the p53 family have been demonstrated to play a crucial role in the development and differentiation of the skin. We show that expression of the TAp63α isoform leads to an upregulation of the cutaneous papillomavirus HPV 20 promoter, which is increased at least three-fold when c-Jun is co-expressed, in contrast to a minimal increase in activity in the presence of c-Jun alone. Co-expression of TAp63α with JunB or JunD, respectively, and in combination, leads to a reduction in the viral promoter activation measured by the expression of TAp63α alone. JunB and JunD also inhibits the additive effect exerted on the TAp63α activation by c-Jun. Co-immunoprecipitation assays demonstrate a complex formation of c-Jun, JunB and JunD with TAp63α through the SAM domain mediating protein–protein interactions, which is characteristic for p63α. Co-expression of p53 mutant R248W not only downregulates the differential modulation of the viral promoter by TAp63α alone and in the presence of the Jun family members, but leads to a reduction in the protein levels of the overexpressed c-Jun, JunB, JunD, as well as TAp63α. This model system provides insight into yet unknown pathways through which TAp63α and Jun may cooperate in the pathogenesis of HPV associated cutaneous lesions.Oncogene (2006) 25, 3914–3923. doi:10.1038/sj.onc.1209420; published online 13 February 2006 [ABSTRACT FROM AUTHOR]

Maf b-Zip transcription factors are involved in both terminal differentiation and oncogenesis. To investigate this apparent contradiction, we used two different primary cell types and performed an extensive analysis of transformation parameters induced by Maf proteins. We show that MafA and c-Maf are potent oncogenes in chicken embryo fibroblasts, while MafB appears weaker. We also provide the first evidence that MafA can confer growth factor independence and promote cell division at low density. Moreover, using MafA as a model, we identified several parameters that are critical for Maf transforming activities. Indeed, MafA ability to induce anchorage-independent cell growth was sensitive to culture conditions. In addition, the transforming activity of MafA was dependent on its phosphorylation state, since mutation on Ser65 impaired its ability to induce growth at low density and anchorage-independent growth. We next examined transforming activity of large Maf proteins in embryonic neuroretina cells, where they are known to induce differentiation. Unlike v-Jun, MafA, MafB and c-Maf did not show oncogenic activity in these cells. Moreover, they counteracted transformation induced by constitutive activation of the Ras/Raf/MEK pathway. Taken together, our results show that Maf proteins could display antagonistic functions in oncogenesis depending on the cellular context, and support a dual role for Maf as both oncogenes and tumor suppressor-like proteins.Oncogene (2006) 25, 1299–1310. doi:10.1038/sj.onc.1209171; published online 17 October 2005 [ABSTRACT FROM AUTHOR]

Estrogen is critical to both normal mammary gland and breast cancer development. Circulating levels of estrogen in premenopausal women are primarily determined by the action of aromatase in ovarian granulosa cells that converts testosterone to estradiol. In the current study, we unraveled an important role of Jun proteins in modulating ovary-specific aromatase expression. Ectopic expression of the Jun proteins in a human granulosa cell line significantly inhibited an ovary-specific promoter (PII) of the aromatase gene, whereas expression of dominant-negative mutants of Jun led to increased promoter activity. The Jun-mediated repression was specific to the aromatase promoter, as Jun proteins stimulated known AP1-responsive promoters in the same cellular context. Both the activation and basic leucine zipper domains of Jun were required for the transcriptional repression. Electrophoretic gel mobility assay showed that endogenous Jun proteins bound to a functionally important cAMP-responsive element (CRE) in the PII promoter-proximal region. Alteration of the CRE-like site impaired both the cAMP-responsive transcriptional activation and Jun-mediated repression. Furthermore, chromatin immunoprecipitation indicated the presence of cJun at the proximal region of the native PII promoter. Taken together, our work suggests that Jun proteins may attenuate estrogen biosynthesis by directly downregulating transcription of the aromatase gene in ovarian granulosa cells.Oncogene (2005) 24, 2236-2246. doi:10.1038/sj.onc.1208415 Published online 31 January 2005 [ABSTRACT FROM AUTHOR]

p21SNFT (21?kDa small nuclear factor isolated from T cells) is a human basic leucine zipper transcription factor that can repress AP-1-mediated transcription. We show here that overexpression of p21SNFT in HepG2 cells leads to repression of matrix metalloproteinase-1 by 70-80%. p21SNFT interacted with Jun at the matrix metalloproteinase-1 promoter-88 Ets/AP-1 enhancer element, where Jun is known to activate transcription via interaction with Fos and Ets proteins. When p21SNFT/Jun dimers bound the element in the presence of Ets, DNA was protected differently than when Fos was paired with Jun. The data suggest a difference in overall conformation between p21SNFT-containing and Fos-containing complexes that may be involved in the repression of matrix metalloproteinase-1 by p21SNFT. Overexpression of p21SNFT led to a reduction in invasiveness of HepG2 cells through type I collagen and reconstituted basement membrane, an effect similar to that obtained via direct immunodepletion of matrix metalloproteinase-1. The results indicate that the mechanism of repression of matrix metalloproteinase-1 by p21SNFT may be exploited in inhibiting pathological matrix remodeling during cancer progression in vivo.Oncogene (2004) 23, 8805-8814. doi:10.1038/sj.onc.1208109 Published online 27 September 2004 [ABSTRACT FROM AUTHOR]

Mesenchymal-epithelial interactions are increasingly considered to be of vital importance for epithelial homeostasis and regeneration. In skin, the transcription factor AP-1 was shown to be critically involved in the communication between keratinocytes and dermal fibroblasts. After skin injury, the release of IL-1 from keratinocytes induces the activity of the AP-1 subunits c-Jun and JunB in fibroblasts leading to a global change in gene expression. To identify AP-1 target genes in fibroblasts, which are involved in the process of cutaneous repair, we performed gene expression profiling of wild-type, c-jun- and junB-deficient fibroblasts in response to IL-1, mimicking the initial phase of wound healing. Using a 15K cDNA collection, over 1000 genes were found to be Jun-dependent and additional 300 clones showed IL-1 responsiveness. Combinatorial evaluation allowed for the dissection of the specific contribution of either AP-1 subunit to gene regulation. Besides previously identified genes that are involved in cutaneous repair, we have identified novel genes regulated during wound healing in vivo and showed their expression by fibroblasts on wound sections. The identification of novel Jun target genes should provide a basis for understanding the molecular mechanisms underlying mesenchymal-epithelial interactions and the critical contribution of AP-1 to tissue homeostasis and repair.Oncogene (2004) 23, 7005-7017. doi:10.1038/sj.onc.1207938 Published online 26 July 2004 [ABSTRACT FROM AUTHOR]

Targets of the oncogenic transcription factor v-Jun in the murine cell line C3H 10T1/2 cells have been identified using DNA microarrays. Two targets, Akap12 and Marcks, are downregulated in transformed cells and are known tumor suppressor genes. Overexpression of either Akap12 or Marcks in v-Jun-transformed cells reverses the transformed phenotype and leads to the re-expression of the other tumor suppressor gene, suggesting that these two genes cooperate in the establishment of the nontransformed state. Reverted cells continue to express v-Jun at high levels and also re-express c-Jun, which is normally repressed by v-Jun. A panel of six cell lines has been generated to evaluate the expression levels of other v-Jun targets in 10T1/2 cells. With these cells, we find that the upregulated target Sprr1a has an expression pattern that correlates with the transformed phenotype.Oncogene (2004) 23, 5703-5706. doi:10.1038/sj.onc.1207737 Published online 10 May 2004 [ABSTRACT FROM AUTHOR]

c-Fos and v-Fos belong to a group of proteins forming the transcription factor AP-1 that is important for regulation of proliferation, differentiation and programmed cell death in multiple cell types. In this study, we examined the role of c-Fos and v-Fos proteins in v-myb-transformed BM2 monoblasts. We show that while the v-Fos protein prolongs the G0G1 phase of the BM2 cell cycle, c-Fos leaves the cell cycle unaffected and, rather, induces programmed cell death. The apoptosis-promoting activity of the c-Fos protein is markedly enhanced in cells cultivated under serum-free conditions. c-Fos-induced apoptosis of BM2 cells occurred in the presence of Bcl-2 and was not dependent on the transcription activation function of the c-Fos protein. No differentiation-promoting activity of the Fos proteins was observed. The effects of Fos proteins on BM2 cells differ from those induced by Jun proteins, suggesting differential roles of individual components of the AP-1 transcription factor in regulation of essential cellular processes. [ABSTRACT FROM AUTHOR]

The v-myb oncogene of avian myeloblastosis virus transforms myelomonocytic cells in vitro. The line of v-myb-transformed chicken monoblasts BM2 can be induced to terminal differentiation using phorbol esters. The fact that Jun proteins are up-regulated in the phorbol ester-treated BM2 cells prompted us to investigate the role of the Jun proteins in regulation of myeloid differentiation. We ectopically expressed v-jun and c-jun in BM2 cells and evaluated their effects on differentiation and proliferation. c-Jun up-regulated the transactivation activity of v-Myb and induced a proliferation block and differentiation of BM2 cells. In contrast, v-Jun down-regulated v-Myb transactivation causing no dramatic effects on BM2 cells. This confirms that there is no strong correlation between transcriptional activation and strength of oncogenic transformation by v-Myb. Both c-Jun and v-Jun proteins affected sensitivity of BM2 cells to retinoic acid and phorbol ester. Sensitivity of BM2 cells to retinoic acid was enhanced by both Jun proteins, while sensitivity to phorbol 12-myristate 13-acetate was reduced by v-Jun. These data suggest thate Jun plays a major role in macrophage differentiation. [ABSTRACT FROM AUTHOR]

In order to adapt to and to cope with an often hostile host environment, many viruses have evolved to encode products that are homologous to cellular proteins. These proteins exploit the existing host machinery and allow viruses to readily integrate into the host functional network. As a result, viruses are able to maneuver their journey seemingly effortlessly inside the host cell to achieve ultimate survival. Such molecular mimicries sometime go overboard, allowing viruses to overtake the cellular pathways or evade the immune system as do many of the retroviral oncogenes. Retroviral oncogenes are derived directly from host genes, and they are virtually identical to host genes in sequences except those mutations that make them unregulatable by host. Oncogenic herpesviruses also encode oncogenes, or transforming genes, which have independently evolved and are distantly related to host genes. However, these genes do share consensus structural motifs with cellular genes involved in cell growth and apoptosis and are functional analogues to host genes. The Marek's disease virus oncoprotein, MEQ, is one such example. MEQ is a basic region-leucine zipper (bZIP) transactivator which shares extensive homology with the Jun/Fos family of transcription factors within the bZIP domain, but not in other regions. Like all other bZIP proteins, MEQ is capable of dimerizing with itself and with a variety of bZIP partners including c-Jun, B-Jun, c-Fos, CREB, ATF-1, ATF-2, and SNF. MEQ-Jun heterodimers bind to a TRE/CRE-like sequence in the meq promoter region and have been shown to up-regulate MEQ expression in both chicken embryo fibroblasts and F9 cells. In addition, the bZIP and transactivation domains are interchangeable between MEQ and c-Jun in terms of transforming potential; i.e. MEQ can functionally substitute for c-Jun. These properties enable MEQ to engage in host cell processes by disguising itself as c-Jun. On the other hand, there are properties of MEQ notably different from c-Jun, which include its capability to bind RNA, to bind a CACAC-bent DNA structure as a homodimer, to inhibit apoptosis, and to interact with CDK2. MEQ’s subcellular localization in the nucleolus and coiled body, is also different from Jun/Fos family of transactivators. These unique features may provide the MEQ with additional facility in regulating MDV replication, establishing latency, and cellular transformation. In this review, we will attempt to summarize the past research progress on MDV meq, with a focused on the similarities and differences between MEQ and cellular proteins, and between MEQ and other viral oncoproteins. [ABSTRACT FROM AUTHOR]

In order to investigate the regulatory mechanisms involved in the expression of fos and jun family members by glucocorticoids, and the effect of ras transformation in intestinal epithelial cells, we used the rat cell line IEC-6. Dexamethasone treatment induced transiently c-jun mRNAs, in contrast to the sustained expression of c-fos, whereas its effect on junB expression resulted in a later increase. Dexamethasone-dependent stimulation of c-fos and c-jun was modulated predominantly at the level of transcription. Sustained levels of induced c-fos and c-jun proteins were observed after dexamethasone treatment. AP-1 DNA-binding capacity of c-fos, and to a smaller extent c-jun, was increased by glucocorticoids later than after serum treatment. To analyse the effect of ras on the glucocorticoid response of AP-1 components, we studied several IEC-6 cell clones transformed by the Ha-ras oncogene. In comparison to normal cells, these transformants displayed increased AP- 1 DNA-binding activity with higher levels of junB and variable levels of c-jun in the AP-1 complex. Ras transformation repressed the growth-inhibitory properties of glucocorticoids. Furthermore, ras inhibited the glucocorticoid-dependent induction of c-fos protein and mRNA, leading to changes in AP-1 composition as compared to normal cells. As assessed by transient transfection luciferase assays, glucocorticoids induced significantly a minimal promoter containing 3 copies of an AP-1 DNA-binding site as well as the murine c-fos -276 to +112 promoter in non-transformed cell lines. In contrast, glucocorticoid addition did not induce these constructs in two ras transformed cells. These results suggest that ras negatively modulates specific responses of intestinal epithelial cells to glucocorticoids. [ABSTRACT FROM AUTHOR]

The mammalian proto-oncogenes c-jun and c-fos are situated at the end of multiple signal transduction pathways and activation of their products Jun and Fos, components of the transcription factor AP-1, are able to regulate gene transcription in response to extracellular stimuli. Djun and Dfos, the products of the Drosophila proto-oncongenes Djun and Dfos, are similar in size and sequence to their mammalian counterparts c-Jun and c-Fos and are related to their mammalian counterparts by their antigenic properties. However, very little is known about how they are regulated through signal transduction pathways. This paper has investigated the response of their mRNA abundance levels to three signal transduction pathways in Drosophila cultured cells. Various agonists and anagonists that stimulate and inhibit specific enzymes in the pathways have been tested. The results suggest that Djun and Dfos mRNA are continuously expressed and their abundance levels are transiently regulated by multiple signaling pathways, the peak response coming at 1–2 hours after perturbation. Dfos is more highly regulated than Djun which is only modulated. The receptor tyrosine kinase pathways positively regulate Dfos and Djun. The cAMP-mediated pathway positively regulates Dfos but negatively regulates Djun. The protein kinase C-activated pathway does not affect Djun whereas it negatively regulates Dfos. [ABSTRACT FROM AUTHOR]

Dimerisation of leucine zippers results from the parallel association of α-helices to form a coiled coil. Coiled coils comprise a heptad repeat, denoted as ( abcdefg), where residues at positions a and d are hydrophobic and constitute the core of the dimer interface. Charged amino acids at the e and g positions of the coiled coil are thought to be the major influence on dimerisation specificity through the formation of attractive and repulsive interhelical electrostatic interactions. However, the variability of a-position residues in leucine zipper transcription factors prompted us to investigate their influence on dimerisation specificity. We demonstrate that mutation of a single interfacial a-position Ala residue to either Val, Ile or Leu significantly alters the homo- and heterodimerisation specificities of the leucine zipper domain from the c-Jun transcription factor. These results illustrate the importance of a-position residues in controlling leucine zipper dimerisation specificity in addition to providing substantial contributions to dimer stability. [ABSTRACT FROM AUTHOR]

Jun and Fos, b-ZIP transcription factors, form a heterodimer and bind to DNA enhancer elements, thereby regulating the expression of target genes. The present study was undertaken to investigate the molecular mechanism underlying nuclear translocation of the Jun/Fos complex. For this purpose, normal rat kidney cells were microinjected with a DNA expression vector containing wild-type or mutant c- or v- jun together with c- or v- fos, followed by detection of the subcellular localization of Jun or Fos by immunofluorescence staining. The nuclear accumulation of Fos was markedly enhanced by the presence of wild-type Jun, but not by Jun mutants lacking nuclear targeting or zipper dimerization functions, implying that Jun and Fos mutually interact via their leucine zippers and translocate from the cytoplasm to the nucleus using the markedly stronger nuclear localization signal of Jun. [ABSTRACT FROM AUTHOR]

Interactions between proteins affect a wide variety of biological processes, such as signal transduction and control of gene expression. In order to facilitate the study of protein-protein interactions we have developed a new method for specifically detecting the heterodimerization of two heterologous proteins in the bacterium Escherichia coli. The assay is based on the simultaneous use of protein fusions with an altered specificity and a wild-type LexA repressor DNA-binding domain. We have tested this system with two well known eukaryotic dimerization domains (the Fos and Jun leucine zippers). The two interacting proteins were, respectively, fused to a wild-type and a mutant LexA DNA-binding domain. Their hetero-association is specifically measured by the transcriptional repression of a reporter gene ( lacZ) controlled by a hybrid operator containing a wild-type half-site (CTGT) and a mutated operator half-site (CCGT). The hybrid operator/lacZ construct was integrated into the chromosome of the reporter strain (SU202) to avoid possible artefacts due to variations in plasmid copy number. This method should be particularly useful in those cases where one or both partners are also able to form homodimers, since the assay described here is sensitive only to the formation of heterodimers. Furthermore, this assay gives rise to a screenable red/white phenotype on MacConkey-lactose indicator plates, allowing for a genetic study of the specificity of the interaction. [ABSTRACT FROM AUTHOR]

The epidermis is a tissue that undergoes a very complex and tightly controlled differentiation program. The elaboration of this program is generally flawless, resulting in the production of an effective protective barrier for the organism. Many of the genes expressed during keratinocyte differentiation are expressed in a coordinate manner; this suggests that common regulatory models may emerge. The simplest model envisions a 'common regulatory element' that is possessed by all genes that are regulated together (e.g., involucrin and transglutaminase type 1). Studies to date, however, have not identified any such elements and, if anything, the available studies suggest that appropriate expression of each gene is achieved using sometime subtly and sometime grossly different mechanisms. Recent studies indicate that a variety of transcription factors (AP1, AP2, POU domain, Sp1, STAT factors) are expressed in the epidermis and, in many cases, multiple members of several families are present (e.g., AP1 and POU domain factors). The simultaneous expression of multiple members of a single transcription factor family provides numerous opportunities for complex regulation. Some studies suggest that specific members of these families interact with specific keratinocyte genes. The best studied of these families in epidermis is the AP1 family of factors. All of the known AP1 factors are expressed in epidermis [52] and each is expressed in a specific spatial pattern that suggests the potential to regulate multiple genes. It will be important to determine the role of each of these members in regulating keratinocyte gene expression. Finally, information is beginning to emerge regarding signal transduction in keratinocytes. Some of the early events in signal transduction have been identified (e.g., PLC and PKC activation, etc.) and some of the molecular targets of these pathways (e.g., AP1 transcription factors) are beginning to be identified. Eventually we can expect to elucidation of all of the steps between the interaction of the stimulating agent with its receptor and the activation of target gene expression. [ABSTRACT FROM AUTHOR]

Various members of the bZip and bHLH-Zip families of eukaryotic transcription factors,including Jun, Fos, and Myc, have been identified as oncoproteins; mutation or deregulatedexpression of these proteins leads to certain types of cancer. These proteins can only bind totheir cognate DNA enhancer sites following homodimerization, or heterodimerization withanother family member, via their leucine zipper domain. Thus, a novel anticancer strategywould be to inhibit dimerization of these proteins, thereby blocking their DNA binding andtransactivation functions. In this paper we show that it is possible to rationally design leucinezipper peptides that bind with high affinity to the leucine zipper dimerization domains of c-Jun and c-Fos, thus preventing the formation of functional c-Jun homodimers and c-Jun:c-Fosheterodimers; we refer to such peptides as superzippers (SZs). In vivo, c-Jun:SZ and c-Fos:SZheterodimers should be nonfunctional as they lack one of the two basic domains that areessential for DNA binding. While the transport of a peptidic agent into cells often poses asevere obstacle to its therapeutic use, we show that a 46-residue leucine zipper peptide canbe transported into HeLa cells by coupling it to a 17-residue carrier peptide from theAntennapedia homeodomain, thus paving the way for detailed studies of the therapeuticpotential of superzipper peptides. [ABSTRACT FROM AUTHOR]

The nuclear factor Fos participates in the transcriptional regulation of genes that contain a functional AP-1 binding site. Hyperosmotic stress induces Fos-like immunoreactivity in neurons of the hypothalamus. Fos appears to depend on the co-expression of the nuclear factor Jun, with which it dimerizes, to complete its regulatory role. The immunocytochemical co-localization of both peptides, however, has not been reported. The present study was designed to analyze the distribution of Fos and Jun by double immunofluorescence staining in Long-Evans rats that were osmotically challenged by a single intraperitoneal injection of 1.5 M NaCl. Non-injected and isotonic saline-injected animals were used as controls. Hypertonic saline injection induced Jun immunoreactivity in cell nuclei in the supraoptic nucleus, paraventricular nucleus, and median preoptic nucleus. The immunofluorescence for Jun was strong in the supraoptic and paraventricular nuclei, but weak in the median preoptic nucleus. The immunofluorescence for Fos in all 3 nuclei followed a similar pattern to that for Jun. Double immunofluorescence staining revealed colocalization of Jun with Fos in 87.4% of the cells of the supraoptic nucleus. Neither Jun nor Fos immunofluorescence was detected in control animals. The data support a role for Jun in transcriptional regulation of genes in hypothalamic neurons during acute hyperosmotic stress. Moreover, the findings are compatible with the suggestion that Fos and Jun act cooperatively in the regulation of gene transcription in neuroendocrine systems involved in the control of water balance during acute hyperosmotic stimulation. [ABSTRACT FROM AUTHOR]

The cellular pathophysiology of septic shock is characterized by the activation of genes in response to exposure of cells to bacterial lipopolysaccharide, Tumour necrosis factor-α (TNF-α) or endotoxin induce the activation of two major transcription factors, NF-κB (nuclear factor-kappaB) and AP-1 (activating protein-1), which in turn induce genes involved in chronic and acute inflammatory responses. The activity of both of them is regulated by phosphorylation and subsequent interaction with the coactivator protein CBP (CREB-binding protein). Thus, the limiting CBP may play an important role in the development of critical illness. [ABSTRACT FROM AUTHOR]