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Sandor K.,Debrecen University | Daniel B.,Debrecen University | Daniel B.,Sanford Burnham Prebys Medical Discovery Institute at Lake Nona | Kiss B.,Debrecen University | And 2 more authors.
Biochimica et Biophysica Acta - Gene Regulatory Mechanisms | Year: 2016

Transglutaminase 2 (TGM2) is a ubiquitously expressed multifunctional protein, which participates in various biological processes including thymocyte apoptosis. As a result, the transcriptional regulation of the gene is complex and must depend on the cell type. Previous studies from our laboratory have shown that in dying thymocytes the expression of Tgm2 is induced by external signals derived from engulfing macrophages, such as retinoids, transforming growth factor (TGF)-β and adenosine, the latter triggering the adenylate cyclase signaling pathway. The existence of TGF-β and retinoid responsive elements in the promoter region of Tgm2 has already been reported, but the intergenic regulatory elements participating in the regulation of Tgm2 have not yet been identified. Here we used publicly available results from DNase I hypersensitivity analysis followed by deep sequencing and chromatin immunoprecipitation followed by deep sequencing against CCCTC-binding factor (CTCF), H3K4me3, H3K4me1 and H3K27ac to map a putative regulatory element set for Tgm2 in thymocytes. By measuring eRNA expressions of these putative enhancers in retinoid, rTGF-β or dibutiryl cAMP-exposed thymocytes we determined which of them are functional. By applying ChIP-qPCR against SMAD4, retinoic acid receptor, retinoid X receptor, cAMP response element binding protein, P300 and H3K27ac under the same conditions, we identified two enhancers of Tgm2, which seem to act as integrators of the TGF-β, retinoid and adenylate cyclase signaling pathways in dying thymocytes. Our study describes a novel strategy to identify and characterize the signal-specific functional enhancer set of a gene by integrating genome-wide datasets and measuring the production of enhancer specific RNA molecules. © 2016 Elsevier B.V..

Szaloki N.,Debrecen University | Krieger J.W.,German Cancer Research Center | Komaromi I.,Hungarian Academy of Sciences | Komaromi I.,Debrecen University | And 3 more authors.
Molecular and Cellular Biology | Year: 2015

The c-Fos and c-Jun transcription factors, members of the activator protein 1 (AP-1) complex, form heterodimers and bind to DNA via a basic leucine zipper and regulate the cell cycle, apoptosis, differentiation, etc. Purified c-Jun leucine zipper fragments could also form stable homodimers, whereas c-Fos leucine zipper homodimers were found to be much less stable in earlier in vitro studies. The importance of c-Fos overexpression in tumors and the controversy in the literature concerning c-Fos homodimerization prompted us to investigate Fos homodimerization. Förster resonance energy transfer (FRET) and molecular brightness analysis of fluorescence correlation spectroscopy data from live HeLa cells transfected with fluorescent-proteintagged c-Fos indicated that c-Fos formed homodimers. We developed a method to determine the absolute concentrations of transfected and endogenous c-Fos and c-Jun, which allowed us to determine dissociation constants of c-Fos homodimers (Kd = 6.7 ± 1.7 μM) and c-Fos- c-Jun heterodimers (on the order of 10 to 100 nM) from FRET titrations. Imaging fluorescence cross-correlation spectroscopy (SPIM-FCCS) and molecular dynamics modeling confirmed that c-Fos homodimers were stably associated and could bind to the chromatin. Our results establish c-Fos homodimers as a novel form of the AP-1 complex that may be an autonomous transcription factor in c-Fos-overexpressing tissues and could contribute to tumor development. © 2015, American Society for Microbiology.

Chen J.,Dana-Farber Cancer Institute | Li J.-L.,Sanford Burnham Prebys Medical Discovery Institute at Lake Nona | Chen Z.,University of Florida | Griffin J.D.,Dana-Farber Cancer Institute | Wu L.,University of Florida
BMC Cancer | Year: 2015

Background: Mucoepidermoid carcinoma (MEC) arises from multiple organs and accounts for the most common types of salivary gland malignancies. Currently, patients with unresectable and metastatic MEC have poor long-term clinical outcomes and no targeted therapies are available. The majority of MEC tumors contain a t(11;19) chromosomal translocation that fuses two genes, CRTC1 and MAML2, to generate the chimeric protein CRTC1-MAML2. CRTC1-MAML2 displays transforming activity in vitro and is required for human MEC cell growth and survival, partially due to its ability to constitutively activate CREB-mediated transcription. Consequently, CRTC1-MAML2 is implicated as a major etiologic molecular event and a therapeutic target for MEC. However, the molecular mechanisms underlying CRTC1-MAML2 oncogenic action in MEC have not yet been systematically analyzed. Elucidation of the CRTC1-MAML2-regulated transcriptional program and its underlying mechanisms will provide important insights into MEC pathogenesis that are essential for the development of targeted therapeutics. Methods: Transcriptional profiling was performed on human MEC cells with the depletion of endogenous CRTC1-MAML2 fusion or its interacting partner CREB via shRNA-mediated gene knockdown. A subset of target genes was validated via real-time RT-PCR assays. CRTC1-MAML2-perturbed molecular pathways in MEC were identified through pathway analyses. Finally, comparative analysis of CRTC1-MAML2-regulated and CREB-regulated transcriptional profiles was carried out to assess the contribution of CREB in mediating CRTC1-MAML2-induced transcription. Results: A total of 808 differentially expressed genes were identified in human MEC cells after CRTC1-MAML2 knockdown and a subset of known and novel fusion target genes was confirmed by real-time RT-PCR. Pathway Analysis revealed that CRTC1-MAML2-regulated genes were associated with network functions that are important for cell growth, proliferation, survival, migration, and metabolism. Comparison of CRTC1-MAML2-regulated and CREB-regulated transcriptional profiles revealed common and distinct genes regulated by CRTC1-MAML2 and CREB, respectively. Conclusion: This study identified a specific CRTC1-MAML2-induced transcriptional program in human MEC cells and demonstrated that CRTC1-MAML2 regulates gene expression in CREB-dependent and independent manners. Our data provide the molecular basis underlying CRTC1-MAML2 oncogenic functions and lay a foundation for further functional investigation of CRTC1-MAML2-induced signaling in MEC initiation and maintenance. © 2015 Chen et al.

Sousounis K.,University of Dayton | Qi F.,Sanford Burnham Prebys Medical Discovery Institute at Lake Nona | Yadav M.C.,Sanford Burnham Institute for Medical Research | Millan J.L.,Sanford Burnham Institute for Medical Research | And 6 more authors.
eLife | Year: 2015

Newts have the ability to repeatedly regenerate their lens even during ageing. However, it is unclear whether this regeneration reflects an undisturbed genetic activity. To answer this question, we compared the transcriptomes of lenses, irises and tails from aged newts that had undergone lens regeneration 19 times with the equivalent tissues from young newts that had never experienced lens regeneration. Our analysis indicates that repeatedly regenerated lenses showed a robust transcriptional program comparable to young never-regenerated lenses. In contrast, the tail, which was never regenerated, showed gene expression signatures of ageing. Our analysis strongly suggests that, with respect to gene expression, the regenerated lenses have not deviated from a robust transcriptional program even after multiple events of regeneration throughout the life of the newt. In addition, our study provides a new paradigm in biology, and establishes the newt as a key model for the study of regeneration in relation to ageing. © Sousounis et al.

Chen Z.,University of Florida | Li J.-L.,Sanford Burnham Prebys Medical Discovery Institute at Lake Nona | Lin S.,University of Florida | Cao C.,University of Florida | And 11 more authors.
Journal of Clinical Investigation | Year: 2016

The LKB1 tumor suppressor gene is frequently mutated and inactivated in non-small cell lung cancer (NSCLC). Loss of LKB1 promotes cancer progression and influences therapeutic responses in preclinical studies; however, specific targeted therapies for lung cancer with LKB1 inactivation are currently unavailable. Here, we have identified a long noncoding RNA (lncRNA) signature that is associated with the loss of LKB1 function. We discovered that LINC00473 is consistently the most highly induced gene in LKB1-inactivated human primary NSCLC samples and derived cell lines. Elevated LINC00473 expression correlated with poor prognosis, and sustained LINC00473 expression was required for the growth and survival of LKB1-inactivated NSCLC cells. Mechanistically, LINC00473 was induced by LKB1 inactivation and subsequent cyclic AMP-responsive element-binding protein (CREB)/CREB-regulated transcription coactivator (CRTC) activation. We determined that LINC00473 is a nuclear lncRNA and interacts with NONO, a component of the cAMP signaling pathway, thereby facilitating CRTC/CREB-mediated transcription. Collectively, our study demonstrates that LINC00473 expression potentially serves as a robust biomarker for tumor LKB1 functional status that can be integrated into clinical trials for patient selection and treatment evaluation, and implicates LINC00473 as a therapeutic target for LKB1-inactivated NSCLC. © 2016, American Society for Clinical Investigation. All rights reserved.

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