Jun Activation Domain-binding Protein Research Articles

Oxidative Stress-Mediated RUNX3 Mislocalization Occurs Via Jun Activation Domain-Binding Protein 1 and Histone Modification.

Runt domain transcription factor 3 (RUNX3) suppresses many different cancer types and is disabled by mutations, epigenetic repression, or cytoplasmic mislocalization. In this study, we investigated whether oxidative stress is associated with RUNX3 accumulation from the nucleus to the cytoplasm in terms of histone modification. Oxidative stress elevated histone deacetylase (HDAC) level and lowered that of histone acetyltransferase. In addition, oxidative stress decreased the expression of mixed lineage leukemia (MLL), a histone methyltransferase, but increased the expression of euchromatic histone-lysine N-methyltransferase 2 (EHMT2/G9a), which is also a histone methyltransferase. Moreover, oxidative stress-induced RUNX3 phosphorylation, Src activation, and Jun activation domain-binding protein 1 (JAB1) expression were inhibited by knockdown of HDAC and G9a, restoring the nuclear localization of RUNX3 under oxidative stress. Cytoplasmic RUNX3 localization was followed by oxidative stress-induced histone modification, activated Src along with RUNX3 phosphorylation, and induction of JAB1, resultingin RUNX3 inactivation.

Kinase Inhibitor Protein 1 and Jun Activation Domain Binding Protein 1 as Molecular Targets of a Human Tongue Cancer Cells Induced by Ethanolic Extract of Salacca zalacca peel

Salacca zalacca (gaertn.) voss is an Indonesian tropical fruit which is a superior commodity from Sleman city, Yogyakarta, Indonesia. Its peel contains the main compounds which have various therapeutic effects. In the present study, Kinase inhibitor protein 1(Kip 1) and Jun activation domain binding protein 1(Jab 1) as molecular targets of a human tongue cancer (H357) cells induced by ethanolic extract of Salacca zalacca peel was examined.

Interaction between SCP3 and JAB1 Confers Cancer Therapeutic Resistance and Stem-like Properties through EGF Expression.

Synaptonemal complex protein 3 (SCP3), a member of the Cor1 family, has been implicated in cancer progression, and therapeutic resistance, as well as cancer stem cell (CSC)-like properties. Previously, we demonstrated that SCP3 promotes these aggressive phenotypes via hyperactivation of the AKT signaling pathway; however, the underlying mechanisms responsible for SCP3-induced AKT activation remain to be elucidated. In this study, we demonstrated that the EGF-EGFR axis is the primary route through which SCP3 acts to activate AKT signaling. SCP3 triggers the EGFR-AKT pathway through transcriptional activation of EGF. Notably, neutralization of secreted EGF by its specific monoclonal antibody reversed SCP3-mediated aggressive phenotypes with a concomitant reversal of EGFR-AKT activation. In an effort to elucidate the molecular mechanisms underlying SCP3-induced transcriptional activation of EGF, we identified Jun activation domain-binding protein 1 (JAB1) as a binding partner of SCP3 using a yeast two-hybrid (Y2H) assay system, and we demonstrated that SCP3 induces EGF transcription through physical interaction with JAB1. Thus, our findings establish a firm molecular link among SCP3, EGFR, and AKT by identifying the novel roles of SCP3 in transcriptional regulation. We believe that these findings hold important implications for controlling SCP3high therapeutic-refractory cancer.

Identification of a seven-long non-coding RNA signature associated with Jab1/CSN5 in predicting hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a leading cause of cancer death worldwide, accounting for over 700,000 deaths each year. The lack of predictive and prognostic biomarkers for HCC, with effective therapy, remains a significant challenge for HCC management. Long non-coding RNAs (lncRNAs) play a key role in tumorigenesis and have clinical value as potential biomarkers in the early diagnosis and prediction of HCC. Jun activation domain-binding protein 1 (Jab1, also known as COP9 signalosome subunit 5, CSN5) is a potential oncogene that plays a critical role in the occurrence of HCC. Here, we performed a comprehensive analysis for Jab1/CSN5-associated lncRNAs to predict the prognosis of HCC. The differentially expressed (DE) lncRNAs between in HCC were analyzed based on the TCGA RNA-seq data. We detected 1031 upregulated lncRNAs in 371 HCC tissues and identified a seven-lncRNA signature strongly correlated with Jab1/CSN5 (SNHG6, CTD3065J16.9, LINC01604, CTD3025N20.3, KB-1460A1.5, RP13-582O9.7, and RP11-29520.2). We further evaluated the prognostic significance of these lncRNAs by GEPIA (http://gepia.cancer-pku.cn/). The expression data in 364 liver tumors indicated that this seven-lncRNA signature could better predict worse survival in HCC patients. Moreover, 35 clinical HCC samples were evaluated to assess the validity and reproducibility of the bioinformatic analysis. We found that the targeted lncRNAs were upregulated, with a strong association with Jab1/CSN5 and prognostic value in HCC. Functional enrichment analysis by Gene Ontology (GO) showed that these seven prognostic lncRNAs exhibit oncogenic properties and are associated with prominent hallmarks of cancer. Overall, our findings demonstrate the clinical implication of Jab1/CSN5 with the seven‐lncRNAs in predicting survival for patients with HCC.

A new activator of esterase D decreases blood cholesterol level through ESD/JAB1/ABCA1 pathway.

Excessively high cholesterol content in the blood leads to nonalcoholfatty liver disease (NAFLD) and arteriosclerosis. Although there are increasing publications and patent applications to lower blood cholesterol with small chemical molecules, limited effective drugs can be available in clinic. It is necessary to uncover new targets and drugs to alleviate high cholesterol. Esterase D (ESD) is abundant in liver and it remains unknown about its role in cholesterol metabolism. Here we reported that small chemical molecule fluorescigenic pyrazoline derivative 5 (FPD5), a new ESDactivator, could effectively reverse high blood cholesterol level and prevent fatty liver and arteriosclerosis in apoE-/- mice fed the high-fat diet. We also observed that FPD5 could reduce oxidized low density lipoprotein (oxLDL)-induced formation of foam cells. To further investigate the mechanism of FPD5 action on blood cholesterol modulation, we found that ESD trigged by FPD5 was aggregated in lysosome and interacted with Jun activation domain binding protein 1 (JAB1). ESD served as a deacetylase to remove Thr89 acetylation of JAB1 and increased its activity; thus,promoting the ATP-binding cassette transporters A1 (ABCA1) to accelerate cholesterol efflux. Our findings demonstrate that FPD5 decreases blood cholesterol level to ameliorate NAFLD and arteriosclerosis through ESD/JAB1/ABCA1 pathway, and ESD functions as a novel nonclassical deacetylase that hydrolyzes serine/threonine acetyl group. Our findings not only highlight that FPD5 may be a pioneer drug for alleviating blood cholesterolbut also indicate that ESD is a potential drug target that promotes cholesterol metabolism.

Nuclear β-catenin expression is positively regulated by JAB1 in human colorectal cancer cells

Wnt/β-catenin signaling is important for development and progression of colorectal cancer (CRC). The degradation complex for β-catenin is functionally impaired in CRC cells, thereby resulting in the accumulation of β-catenin and its translocation into the nucleus. Nuclear β-catenin interacts with and co-activates T cell factor4 (TCF4), resulting in β-catenin/TCF4-dependent transcription. Therefore, nuclear β-catenin has been categorized as the main driving force in the tumorigenesis of CRC. Recent studies reveal that Jun activation domain-binding protein 1 (JAB1) enhances the degradation of seven in absentia homolog-1 (SIAH-1), a putative E3 ubiquitin ligase of β-catenin, and positively regulates the expression of total β-catenin in human CRC cells. An another recent study also shows that nuclear β-catenin is ubiquitinated and degraded by an E3 ubiquitin ligase, tripartite motif-containing protein 33 (TRIM33). However, the regulatory mechanism for the expression of nuclear β-catenin remains to be fully understood. In this study, we have demonstrated that JAB1 positively regulates the expression of nuclear β-catenin, c-MYC as a β-catenin/TCF4 target, and cell cycle regulators, such as Ki-67 and topoisomerase IIα, in human CRC cells. Taken together, these results suggest that JAB1 is considered as a promising target for novel CRC therapy.

The crucial p53-dependent oncogenic role of JAB1 in osteosarcoma in vivo.

Osteosarcoma (OS) is the most common primary bone cancer and ranks amongst the leading causes of cancer mortality in young adults. Jun activation domain binding protein 1 (JAB1) is overexpressed in many cancers and has recently emerged as a novel target for cancer treatment. However, the role of JAB1 in osteosarcoma was virtually unknown. In this study, we demonstrate that JAB1-knockdown in malignant osteosarcoma cell lines significantly reduced their oncogenic properties, including proliferation, colony formation, and motility. We also performed RNA-sequencing analysis in JAB1-knockdown OS cells and identified 4110 genes that are significantly differentially expressed. This demonstrated for the first time that JAB1 regulates a large and specific transcriptome in cancer. We also found that JAB1 is overexpressed in human OS and correlates with a poor prognosis. Moreover, we generated a novel mouse model that overexpresses Jab1 specifically in osteoblasts upon a TP53 heterozygous sensitizing background. Interestingly, by 13 months of age, a significant proportion of these mice spontaneously developed conventional OS. Finally, we demonstrate that a novel, highly specific small molecule inhibitor of JAB1, CSN5i-3, reduces osteosarcoma cell viability and has specific effects on the ubiquitin-proteasome system in OS. Thus, we show for the first time that the overexpression of JAB1 in vivo can result in accelerated spontaneous tumor formation in a p53-dependent manner. In summary, JAB1 might be a unique target for the treatment of osteosarcoma and other cancers.

Nongenetic optical modulation of neural stem cell proliferation and neuronal/glial differentiation

Photostimulation has been widely used in neuromodulation. However, existing optogenetics techniques require genetic alternation of the targeted cell or tissue. Here, we report that neural stem cells (NSCs) constitutionally express blue/red light-sensitive photoreceptors. The proliferation and regulation of NSCs to neuronal or glial cells are wavelength-specific. Our results showed a 4.3-fold increase in proliferation and 2.7-fold increase in astrocyte differentiation for cells under low-power blue monochromatic light exposure (455 nm, 300 μW/cm2). The melanopsin (Opn4)/transient receptor potential channel 6 (TRPC6) non-visual opsin serves as a key photoreceptor response to blue light irradiation. Two-dimensional gel electrophoresis coupled with mass spectrometry further highlighted the Jun activation domain-binding protein 1 (Jab1) as a novel and specific modulator in phototransduction pathways induced by blue light exposure. Quiescent adult NSCs reside in specific regions of the mammalian brain. Therefore, we showed that melanopsin/TRPC6 expressed in these regions and blue light stimulation through optical fibers could directly stimulate the NSCs in vivo. Upconversion nanoparticles (UCNPs) converted deep-penetrating near-infrared (NIR) light into specific wavelengths of visible light. Accordingly, we demonstrated that UCNP-mediated NIR light could be used to modulate in vivo NSC differentiation in a less invasive manner. In the future, this light-triggered system of NSCs will enable nongenetic and noninvasive neuromodulation with therapeutic potential for central nervous system diseases.

Both Ser361 phosphorylation and the C-arrestin domain of thioredoxin interacting protein are important for cell cycle blockade at the G1/S checkpoint.

Thioredoxin interacting protein (TXNIP) is a novel tumor suppressor that is down‐regulated in several cancer tissues and tumor cell lines. Overexpression of TXNIP causes cell cycle arrest at the G1/S checkpoint in the hepatocellular carcinoma cell line HuH‐7. TXNIP contains putative phosphorylation sites, but the effects of its phosphorylation have not been fully characterized. TXNIP also contains two α‐arrestin domains (N‐arrestin and C‐arrestin) whose functions are not fully understood. Here, we reveal an association between TXNIP and cell cycle regulatory proteins (p27kip1, Jun activation domain‐binding protein 1 (JAB1), Cdk2, and cyclin E), suggesting its participation in cell cycle regulation. We observed phosphorylation of TXNIP and used both in vivo and in vitro kinase assays to demonstrate that TXNIP can be phosphorylated by p38 mitogen‐activated protein kinase. Furthermore, we also identified Ser361 in TXNIP as one of the major phosphorylation sites. Cell cycle analysis showed that Ser361 phosphorylation participates in TXNIP‐mediated cell cycle arrest. In addition, the C‐arrestin domain may also play an important role in cell cycle arrest. We also showed that phosphorylation at Ser361 may be important for the association of TXNIP with JAB1 and that the C‐arrestin domain is necessary for the nuclear localization of this molecule. Collectively, these studies reveal that TXNIP participates in cell cycle regulation through association with regulatory proteins, especially JAB1, and that C‐arrestin‐dependent nuclear localization is important for this function. This work may facilitate the development of a new cancer therapy strategy that targets TXNIP as a key molecule inhibiting cancer cell growth via cell cycle blockade at the G1/S checkpoint.

GLYCOLYTIC 2-DEOXY-D-GLUCOSE PERIOCULAR INHIBITOR SEBAGAI TERAPI ADJUVANT PADA RETINOBLASTOMA

Retinoblastoma is the most common intraocular tumor in children. Retinoblastoma tumors consist of areas with high angiogenic activity and other areas with low oxygen pressure conditions. Tumor cells that survive in this hypoxic region have been shown to be resistant to chemotherapy and radiation, namely standard retinoblastoma therapy which selectively targets rapidly dividing cell populations, so that therapy is needed that can reach up to the hypoxic cells. 2-deoxy-D-glucose (2-DG) has been shown to be effective in reducing hypoxic areas in tumors, reducing tumor buds, and inhibiting angiogenesis. to discuss the glycolytic 2-DG inhibitors as adjuvant therapy in retinoblastoma. The authors searched for medical articles in the PubMed and ResearchGate literature databases with the keywords treatment, 2-deoxy-D-glucose, 2-DG, retinoblastoma, and cancer. The words are combined with OR or AND using Boolean logic. Based on the selection according to the inclusion and exclusion criteria, 4 articles were used as the main reference for writing this review literature. 2-DG will disregulate (inhibit) the process of angiogenesis through upregulation of Estrogen Receptor 1 Nuclear (ESR 1), ubiquitin, jun activation domain binding protein 1 (JAB1), G-protein alpha S, and CAPER in the apical part of the tumor and B3GNT1 upregulation , CEPT1, PABPC1, myotrophin, HAX1 in the postero-lateral part of the tumor. H3, DTX1, RPL12, and bone morphogenic (BMP) histones are also upregulated so that hypoxia can be inhibited. With this mechanism, the tumor burden can be suppressed. Glycolytic 2-DG inhibitors with anti-angiogenesis and anti-hypoxic abilities can be developed as adjuvant therapy for advanced retinoblastoma patients.

Expression of Jun activation domain-binding protein 1 and p27 Kip1 in endometrial polyps and uterine leiomyomas

Expression of Jun activation domain-binding protein 1 and p27 Kip1 in endometrial polyps and uterine leiomyomas

Dual gain and loss of cullin 3 function mediates familial hyperkalemic hypertension.

Familial hyperkalemic hypertension is caused by mutations in with-no-lysine kinases (WNKs) or in proteins that mediate their degradation, kelch-like 3 (KLHL3) and cullin 3 (CUL3). Although the mechanisms by which WNK and KLHL3 mutations cause the disease are now clear, the effects of the disease-causing CUL3Δ403-459 mutation remain controversial. Possible mechanisms, including hyperneddylation, altered ubiquitin ligase activity, decreased association with the COP9 signalosome (CSN), and increased association with and degradation of KLHL3 have all been postulated. Here, we systematically evaluated the effects of Cul3Δ403-459 using cultured kidney cells. We first identified that the catalytically active CSN subunit jun activation domain-binding protein-1 (JAB1) does not associate with the deleted Cul3 4-helix bundle domain but instead with the adjacent α/β1 domain, suggesting that altered protein folding underlies the impaired binding. Inhibition of deneddylation with JAB1 siRNA increased Cul3 neddylation and decreased KLHL3 abundance, similar to the Cul3 mutant. We next determined that KLHL3 degradation has both ubiquitin ligase-dependent and -independent components. Proteasomal KLHL3 degradation was enhanced by Cul3Δ403-459; however, autophagic degradation was also upregulated by this Cul3 mutant. Finally, to evaluate whether deficient substrate adaptor was responsible for the disease, we restored KLHL3 to wild-type (WT) Cul3 levels. In the absence of WT Cul3, WNK4 was not degraded, demonstrating that Cul3Δ403-459 itself cannot degrade WNK4; conversely, when WT Cul3 was present, as in diseased humans, WNK4 degradation was restored. In conclusion, deletion of exon 9 from Cul3 generates a protein that is itself ubiquitin-ligase defective but also capable of enhanced autophagocytic KLHL3 degradation, thereby exerting dominant-negative effects on the WT allele.

JAB1 regulates CPNE1-related differentiation via direct binding to CPNE1 in HiB5 hippocampal progenitor cells

Copine1 (CPNE1), has tandem C2 domains and an A domain. We previously demonstrated that CPNE1 directly induces neuronal differentiation via Protein kinase B (AKT) phosphorylation in the hippocampal progenitor cell line, HiB5. To better understand its cellular function, we carried out a yeast two-hybrid screening to find CPNE1 binding partners. Among the identified proteins, Jun activation domain-binding protein 1 (JAB1) appears to directly interact with CPNE1. Between CPNE1 and JAB1, the physical interaction was confirmed in vitro and in vivo. In addition the specific binding regions of CPNE1 and JAB1 was confirmed with truncated mutant assay. Furthermore, our results also demonstrate that AKT phosphorylation and expression of the neuronal marker protein are increased when JAB1 is overexpressed in CPNE1 high expressed HiB5 cells. Moreover, overexpression of both CPNE1 and JAB1 in HiB5 cells effectively increased neurite outgrowth.Collectively, our findings suggest that JAB1 activates the neuronal differentiation ability of CPNE1 through the binding of C2A domain in CPNE1 with MPN domain in JAB1.

Decoction of Chinese Herbal Medicine Fuzheng Kang-Ai Induces Lung Cancer Cell Apoptosis via STAT3/Bcl-2/Caspase-3 Pathway.

Decoction of Chinese herbal medicine (CHM) Fuzheng Kang-Ai (FZKA for short) has been applied as adjuvant treatment strategy in advanced lung cancer patients for decades. We previously showed that FZKA decoction inhibited proliferation of non-small cell lung cancer (NSCLC) cells through activation of AMP-activated protein kinase alpha (AMPKα) signaling pathway, followed by inducing insulin-like growth factor (IGF) binding protein 1 (IGFBP1) and forkhead homeobox type O3a (FOXO3a) proteins, and enhanced the inhibition effect of gefitinib in lung cancer cell growth via inactivating PI3-K/Akt-mediated suppressing of cell surface-associated mucin-1 (MUC1) expression. In this study, we investigated the molecular mechanism by which FZKA decoction affected cell apoptosis in lung cancer cells. Our results show that FZKA induced apoptosis in lung cancer cells. Mechanistically, FZKA activated the caspase-3, PARP, and caspase-9 activities. Both antiapoptotic and proapoptotic proteins from Bcl-2 family were deregulated by FZKA exposure in lung cancer cells. In addition, FZKA reduced protein expressions of signal transducer and activator of transcription 3 (STAT3) and Jun activation domain-binding protein 1 (Jab1), while it concomitantly increased p21 protein. Moreover, the inhibitor of caspase-3 resisted the effect of FZKA on induction of apoptosis. Finally, exogenous overexpression of STAT3 overcame FZKA-inhibited protein expressions of Bcl-2 and myeloid cell leukemia-1 (Mcl-1) as well as Bax and blocked FZKA-induced activities of caspase-3 and caspase-9. Our results show that FZKA decoction promotes lung cancer cell apoptosis through STAT3/Bcl-2/caspase-3 signaling pathways. This study unveils potential novel molecular mechanism by which FZKA controls growth of human lung cancer cells.

JAB1-STAT3 activation loop is associated with recurrence following 5-fluorouracil-based adjuvant chemotherapy in human colorectal cancer.

Jun activation domain-binding protein 1 (JAB1) has been shown to have multiple roles in tumorigenesis, including the degradation of tumor suppressor proteins such as p53, Smad7, Runx3 and the cyclin-dependent kinase inhibitor p27Kip1, and the activation of oncogenic transcription factors, such as c-Jun and hypoxia-inducible factor-1α. In addition, our previous study revealed that JAB1 positively regulates signal transducer and activator of transcription 3 (STAT3) DNA-binding activity in human colon cancer cells. In turn, the oncogenic transcription factor STAT3 positively regulates JAB1 expression, indicative of a positive feedback loop. Furthermore, high JAB1 expression is associated with a poor prognosis in numerous malignant carcinomas. However, the association between JAB1 expression and prognosis in colorectal cancer remains unclear. The aim of the present study was to elucidate the association between JAB1 and STAT3 expression and recurrence in colorectal cancer. In the present study, it was found that high JAB1 expression in primary colorectal cancer tissues is an independent predictor of recurrence following 5-fluorouracil (5-FU)-based adjuvant chemotherapy in colorectal cancer patients, and that high expression of both JAB1 and STAT3 in primary colorectal cancer tissues is associated with a lower recurrence-free survival rate following 5-FU-based adjuvant chemotherapy compared to high expression of only JAB1 or STAT3. Overall, these results suggest that JAB1 is a novel predictive marker of recurrence following 5-FU-based adjuvant chemotherapy in colorectal cancer patients, and that the JAB1-STAT3 activation loop may be a potential therapeutic target in recurrent colorectal cancer following 5-FU-based adjuvant chemotherapy.

Oxidized LDL-induced JAB1 influences NF-\u03baB independent inflammatory signaling in human macrophages during foam cell formation

BackgroundOxidized low-density lipoprotein (oxLDL) mediates the transformation of macrophages (MΦ) to cholesterol-rich foam cells and the release of pro-inflammatory cytokines during atherogenesis. JAB1 (Jun activation domain binding protein-1) is present in all stages of human plaques, involved in the Toll-like receptor-mediated activation of p38 mitogen-activated protein kinase (MAPK) and controls nuclear factor-kappa B (NF-κB) activation. Thus, we were interested in the role of JAB1 during foam cell formation of MΦ after oxLDL exposition.Methods and resultsWe found that JAB1 was present in CD68-immunoreactive (−ir) MΦ in atherosclerotic plaques of apolipoprotein E knockout (ApoE−/−) mice after a high cholesterol/fat diet. Furthermore, differentiated human U937 MΦ - incubated with oxLDL (4 h) to induce foam cell formation – showed a significant increase of JAB1 (50 μg/ml: 1.39 + 0.15-fold; 100 μg/ml: 1.80 + 0.26-fold; 200 μg/ml: 2.05 + 0.30-fold; p < 0.05) on the protein level compared to the control. Independent from JAB1 silencing, we found an increase of total cholesterol (TC), free cholesterol (FC) and cholesteryl ester (CE) after oxLDL exposition. However, siJAB1-MФ showed a reduction of tumor necrosis factor-alpha (TNF-α) (36%; p < 0.05 vs. non-transfected MФ) and interleukin (IL)-6 (30%; p < 0.05 vs. non-transfected MФ) mRNA expression, as well as TNF-α (46%; p < 0.05 vs. non-transfected MФ) and IL-6 (32%; p < 0.05 vs. non-transfected MФ) protein secretion after oxLDL exposition. In parallel with an upregulation of inflammatory cytokines (TNF-α, IL-6) after oxLDL exposition, we found a significant (p < 0.05) increase of 37% in p38 MAPK activation after 4 h oxLDL-treatment, independent from NF-kB signaling. In this context, we showed regional co-localization of JAB1 with p38 MAPK in atherosclerotic plaques of ApoE−/− mice. Moreover, we detected interaction of JAB1 with p38 MAPK in U937 cells.ConclusionWe demonstrate that oxLDL induces JAB1 expression and influences its cellular localization, whereby the p38 MAPK signaling pathway is modified with consequences for inflammation of human MΦ in foam cells and atherosclerotic lesions.

Jab1 is a T2-dependent coactivator or a T3-dependent corepressor of TRB1-mediated gene regulation.

Thyroid hormones (THs) induce pleiotropic effects in vertebrates, mainly through the activation or repression of gene expression. These mechanisms involve thyroid hormone binding to thyroid hormone receptors, an event that is followed by the sequential recruitment of coactivator or corepressor proteins, which in turn modify the rate of transcription. In the present study, we looked for specific coregulators recruited by the long isoform of the teleostean thyroid hormone receptor beta 1 (L-Trb1) when bound to the bioactive TH, 3,5-T2 (T2). We found that jun activation domain-binding protein1 (Jab1) interacts with L-Trb1 + T2 complex. Using both the teleostean and human TRB1 isoforms, we characterized the Jab1-TRB1 by yeast two-hybrid, pull-down and transactivation assays. Our results showed that the TRB1-Jab1 interaction was ligand dependent and involved the single Jab1 nuclear receptor box, as well as the ligand-binding and N-terminal domains of TRB1. We also provide evidence of ligand-dependent, dual coregulatory properties of Jab1. Indeed, when T2 is bound to L-Trb1 or hTRB1, Jab1 acts as a coactivator of transcription, whereas it has corepressor activity when interacting with the T3-bound S-Trb1 or hTRB1. These mechanisms could explain some of the pleiotropic actions exerted by THs to regulate diverse biological processes.

Jab1 promotes glioma cell proliferation by regulating Siah1/β-catenin pathway.

Jab1 (Jun activation domain-binding protein 1), also known as CSN5 (COP9 signalosome subunit 5), is frequently overexpressed in several cancer types. However, the biological functions and the molecular mechanisms of the Jab1 protein in human gliomas have not been investigated. In this study, we found that Jab1 protein was increasingly expressed in human glioma tissues comparing with normal brain tissues (Non-tumor). This suggested that Jab1 might be involved in the development of glioma. Thus, the role of Jab1 in glioma cell proliferation was investigated using Jab1 loss- and gain-of-function. The results showed that downregulation of Jab1 significantly inhibited glioma cell proliferation, while overexpression of Jab1 promoted it. Further investigation on molecular targets revealed that silencing of Jab1 obviously increased the p53 protein level thereby promoting the transcription of ubiquitin ligase Siah1 (Seven in absentia homolog 1), which aggravates the degradation of β-catenin. In contrast, overexpression of Jab1 had the opposite effect. Taken together, these findings suggest that Jab1 promotes glioma cell proliferation and increased expression of Jab1 in glioma patients may amplify β-catenin signaling to contribute to glioma cell proliferation.

Associations and prognostic significance of p27Kip1, Jab1 and Skp2 in non-Hodgkin lymphoma.

Non-Hodgkin lymphoma (NHL) is a primary tumor arising in lymph nodes and lymphoid tissue. The incidence of NHL is increasing at an annual rate of 3%. The human Jun activation domain-binding protein 1/COP9 signalosome subunit 5 (Jab1/CSN5) is a negative regulator of the cell cycle inhibitor p27Kip1 and abnormal expression of Jab1 is correlated with reduced p27 expression and associated with advanced tumor stage and poor prognosis in several human cancers. F-box protein S-phase kinase-interacting protein-2 (Skp2), the substrate recognition subunit of the Skp1-Cul1-F-box protein ubiquitin protein ligase complex, is required for the ubiquitination and consequent degradation of p27. The Skp2 protein is overexpressed in several human cancers and is associated with the degree of differentiation and the prognosis. The aim of the present study was to investigate the expression status of p27Kip1, Jab1 and Skp2 by immunohistochemistry, and assess their prognostic significance in patients with NHL. Immunohistochemical analysis revealed an inverse association between Jab1 and p27 in NHL tissue samples. Kaplan-Meier analysis demonstrated that Jab1 overexpression, Skp2 overexpression and low p27 expression were significantly associated with poor prognosis. Among clinicopathological parameters, overexpression of Jab1 was significantly associated with tumor size and International Prognostic Index (IPI), whereas Skp2 expression was significantly associated with metastasis and IPI. These findings suggest that the overexpression of Jab1 or Skp2 plays an important role in the pathogenesis of NHL. Thus, the expression of p27Kip1, Jab1 and Skp2 provided a clinical reference for the treatment of NHL.

Ligand independent aryl hydrocarbon receptor inhibits lung cancer cell invasion by degradation of Smad4

The aryl hydrocarbon receptor (AhR) is a ligand-dependent-activated transcriptional factor that regulates the metabolism of xenobiotic and endogenous compounds. Although AhR plays a crucial role in air toxicant-induced carcinogenesis, AhR expression was shown to negatively regulate tumorigenesis. Therefore, in the present study, we investigated the effect of AhR without ligand treatment on cancer invasion in lung cancer cell lines. Lung cancer cells expressing lower levels of AhR showed higher invasion ability (H1299 cells) compared with cells expressing higher levels of AhR (A549 cells). Overexpression of AhR in H1299 cells inhibited the invasion ability. We found that vimentin expression was inhibited in AhR-overexpressing H1299 cells. Additionally, the expression of EMT-related transcriptional factors Snail and ID-1 decreased. Interestingly, we found that Smad4 degradation was induced in AhR-overexpressing H1299 cells. Our data showed that AhR could interact with Jun-activation domain binding protein (Jab1) and Smad4, which may cause degradation of Smad4 by the proteasome. Our data suggest that AhR affects the transforming growth factor-β signaling pathway by inducing Smad4 degradation by the proteasome and suppressing tumor metastasis via epithelial to mesenchymal transition reduction in lung cancer cells.