@article{OttoKastnerSchmidtetal.2022, author = {Otto, Christoph and Kastner, Carolin and Schmidt, Stefanie and Uttinger, Konstantin and Baluapuri, Apoorva and Denk, Sarah and Rosenfeldt, Mathias T. and Rosenwald, Andreas and Roehrig, Florian and Ade, Carsten P. and Schuelein-Voelk, Christina and Diefenbacher, Markus E. and Germer, Christoph-Thomas and Wolf, Elmar and Eilers, Martin and Wiegering, Armin}, title = {RNA polymerase I inhibition induces terminal differentiation, growth arrest, and vulnerability to senolytics in colorectal cancer cells}, series = {Molecular Oncology}, volume = {16}, journal = {Molecular Oncology}, number = {15}, doi = {10.1002/1878-0261.13265}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-312806}, pages = {2788-2809}, year = {2022}, abstract = {Ribosomal biogenesis and protein synthesis are deregulated in most cancers, suggesting that interfering with translation machinery may hold significant therapeutic potential. Here, we show that loss of the tumor suppressor adenomatous polyposis coli (APC), which constitutes the initiating event in the adenoma carcinoma sequence for colorectal cancer (CRC), induces the expression of RNA polymerase I (RNAPOL1) transcription machinery, and subsequently upregulates ribosomal DNA (rDNA) transcription. Targeting RNAPOL1 with a specific inhibitor, CX5461, disrupts nucleolar integrity, and induces a disbalance of ribosomal proteins. Surprisingly, CX5461-induced growth arrest is irreversible and exhibits features of senescence and terminal differentiation. Mechanistically, CX5461 promotes differentiation in an MYC-interacting zinc-finger protein 1 (MIZ1)- and retinoblastoma protein (Rb)-dependent manner. In addition, the inhibition of RNAPOL1 renders CRC cells vulnerable towards senolytic agents. We validated this therapeutic effect of CX5461 in murine- and patient-derived organoids, and in a xenograft mouse model. These results show that targeting ribosomal biogenesis together with targeting the consecutive, senescent phenotype using approved drugs is a new therapeutic approach, which can rapidly be transferred from bench to bedside.}, language = {en} } @phdthesis{Solvie2023, author = {Solvie, Daniel Alexander}, title = {Molecular Mechanisms of MYC as Stress Resilience Factor}, doi = {10.25972/OPUS-30539}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-305398}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2023}, abstract = {Cancer is one of the leading causes of death worldwide. The underlying tumorigenesis is driven by the accumulation of alterations in the genome, eventually disabling tumor suppressors and activating proto-oncogenes. The MYC family of proto-oncogenes shows a strong deregulation in the majority of tumor entities. However, the exact mechanisms that contribute to MYC-driven oncogenesis remain largely unknown. Over the past decades, the influence of the MYC protein on transcription became increasingly apparent and was thoroughly investigated. Additionally, in recent years several publications provided evidence for so far unreported functions of MYC that are independent of a mere regulation of target genes. These findings suggest an additional role of MYC in the maintenance of genomic stability and this role is strengthened by key findings presented in this thesis. In the first part, I present data revealing a pathway that allows MYC to couple transcription elongation and DNA double-strand break repair, preventing genomic instability of MYC-driven tumor cells. This pathway is driven by a rapid transfer of the PAF1 complex from MYC onto RNAPII, a process that is mediated by HUWE1. The transfer controls MYC-dependent transcription elongation and, simultaneously, the remodeling of chromatin structure by ubiquitylation of histone H2B. These regions of open chromatin favor not only elongation but also DNA double-strand break repair. In the second part, I analyze the ability of MYC proteins to form multimeric structures in response to perturbation of transcription and replication. The process of multimerization is also referred to as phase transition. The observed multimeric structures are located proximal to stalled replication forks and recruit factors of the DNA-damage response and transcription termination machinery. Further, I identified the HUWE1-dependent ubiquitylation of MYC as an essential step in this phase transition. Cells lacking the ability to form multimers display genomic instability and ultimately undergo apoptosis in response to replication stress. Both mechanisms present MYC as a stress resilience factor under conditions that are characterized by a high level of transcriptional and replicational stress. This increased resilience ensures oncogenic proliferation. Therefore, targeting MYC's ability to limit genomic instability by uncoupling transcription elongation and DNA repair or disrupting its ability to multimerize presents a therapeutic window in MYC-dependent tumors.}, subject = {MYC}, language = {en} } @phdthesis{Hofstetter2022, author = {Hofstetter, Julia Eva Ines}, title = {MYC shapes the composition of RNA polymerase II through direct recruitment of transcription elongation factors}, doi = {10.25972/OPUS-24035}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-240358}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2022}, abstract = {The transcription factor MYC is a onco-protein, found to be deregulated in many human cancers. High MYC levels correlate with an aggressive tumor outcome and poor survival rates. Despite MYC being discovered as an oncogene already in the 1970s, how MYC regulates transcription of its target genes, which are involved in cellular growth and proliferation, is not fully understood yet. In this study, the question how MYC influences factors interacting with the RNA polymerase II ensuring productive transcription of its target genes was addressed using quantitative mass spectrometry. By comparing the interactome of RNA polymerase II under varying MYC levels, several potential factors involved in transcriptional elongation were identified. Furthermore, the question which of those factors interact with MYC was answered by employing quantitative mass spectrometry of MYC itself. Thereby, the direct interaction of MYC with the transcription elongation factor SPT5, a subunit of the DRB-sensitivity inducing factor, was discovered and analyzed in greater detail. SPT5 was shown to be recruited to chromatin by MYC. In addition, the interaction site of MYC on SPT5 was narrowed down to its evolutionary conserved NGN-domain, which is the known binding site for SPT4, the earlier characterized second subunit of the DRB-sensitivity inducing factor. This finding suggests a model in which MYC and SPT4 compete for binding the NGN-domain of SPT5. Investigations of the SPT5-interacting region on MYC showed binding of SPT5 to MYC's N-terminus including MYC-boxes 0, I and II. In order to analyze proteins interacting specifically with the N-terminal region of MYC, a truncated MYC-mutant was used for quantitative mass spectrometric analysis uncovering reduced binding for several proteins including the well-known interactor TRRAP and TRRAP-associated complexes. Summarized, ...}, subject = {Transkription }, language = {en} } @article{HartmannReisslandMaieretal.2021, author = {Hartmann, Oliver and Reissland, Michaela and Maier, Carina R. and Fischer, Thomas and Prieto-Garcia, Cristian and Baluapuri, Apoorva and Schwarz, Jessica and Schmitz, Werner and Garrido-Rodriguez, Martin and Pahor, Nikolett and Davies, Clare C. and Bassermann, Florian and Orian, Amir and Wolf, Elmar and Schulze, Almut and Calzado, Marco A. and Rosenfeldt, Mathias T. and Diefenbacher, Markus E.}, title = {Implementation of CRISPR/Cas9 Genome Editing to Generate Murine Lung Cancer Models That Depict the Mutational Landscape of Human Disease}, series = {Frontiers in Cell and Developmental Biology}, volume = {9}, journal = {Frontiers in Cell and Developmental Biology}, issn = {2296-634X}, doi = {10.3389/fcell.2021.641618}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-230949}, year = {2021}, abstract = {Lung cancer is the most common cancer worldwide and the leading cause of cancer-related deaths in both men and women. Despite the development of novel therapeutic interventions, the 5-year survival rate for non-small cell lung cancer (NSCLC) patients remains low, demonstrating the necessity for novel treatments. One strategy to improve translational research is the development of surrogate models reflecting somatic mutations identified in lung cancer patients as these impact treatment responses. With the advent of CRISPR-mediated genome editing, gene deletion as well as site-directed integration of point mutations enabled us to model human malignancies in more detail than ever before. Here, we report that by using CRISPR/Cas9-mediated targeting of Trp53 and KRas, we recapitulated the classic murine NSCLC model Trp53fl/fl:lsl-KRasG12D/wt. Developing tumors were indistinguishable from Trp53fl/fl:lsl-KRasG12D/wt-derived tumors with regard to morphology, marker expression, and transcriptional profiles. We demonstrate the applicability of CRISPR for tumor modeling in vivo and ameliorating the need to use conventional genetically engineered mouse models. Furthermore, tumor onset was not only achieved in constitutive Cas9 expression but also in wild-type animals via infection of lung epithelial cells with two discrete AAVs encoding different parts of the CRISPR machinery. While conventional mouse models require extensive husbandry to integrate new genetic features allowing for gene targeting, basic molecular methods suffice to inflict the desired genetic alterations in vivo. Utilizing the CRISPR toolbox, in vivo cancer research and modeling is rapidly evolving and enables researchers to swiftly develop new, clinically relevant surrogate models for translational research.}, language = {en} } @phdthesis{Endres2021, author = {Endres, Theresa}, title = {PAF1 complex and MYC couple transcription elongation with double-strand break repair}, doi = {10.25972/OPUS-24955}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-249557}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2021}, abstract = {The oncogene MYC is deregulated and overexpressed in a high variety of human cancers and is considered an important driver in tumorigenesis. The MYC protein binds to virtually all active promoters of genes which are also bound by the RNA Polymerase II (RNAPII). This results in the assumption that MYC is a transcription factor regulating gene expression. The effects of gene expression are weak and often differ depending on the tumor entities or MYC levels. These observations could argue that the oncogene MYC has additional functions independent of altering gene expression. In relation to this, the high diversity of interaction partners might be important. One of them is the RNAPII associated Factor I complex (PAF1c). In this study, direct interaction between PAF1c and MYC was confirmed in an in-vitro pulldown assay. ChIP sequencing analyses revealed that knockdown of PAF1c components resulted in reduced MYC occupancy at active promoters. Depletion or activation as well as overexpression of MYC led to reduced or enhanced global occupancy of PAF1c in the body of active genes, arguing that MYC and PAF1c bind cooperatively to chromatin. Upon PAF1c knockdown cell proliferation was reduced and additionally resulted in an attenuation of activation or repression of MYC-regulated genes. Interestingly, knockdown of PAF1c components caused an accumulation in S-phase of cells bearing oncogenic MYC levels. Remarkably, enhanced DNA damage, measured by elevated gH2AX and pKAP1 protein levels, was observed in those cells and this DNA damage occurs specifically during DNA synthesis. Strikingly, MYC is involved in double strand break repair in a PAF1c-dependent manner at oncogenic MYC levels. Collectively the data show that the transfer of PAF1c from MYC onto the RNAPII couples the transcriptional elongation with double strand break repair to maintain the genomic integrity in MYC-driven tumor cells.}, language = {en} } @phdthesis{Baluapuri2021, author = {Baluapuri, Apoorva}, title = {Molecular Mechanisms of MYC's impact on Transcription Elongation}, doi = {10.25972/OPUS-24380}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-243806}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2021}, abstract = {Expression of the MYC oncoprotein, which binds the DNA at promoters of most transcribed genes, is controlled by growth factors in non-tumor cells, thus stimulating cell growth and proliferation. Here in this thesis, it is shown that MYC interacts with SPT5, a subunit of the RNA polymerase II (Pol II) elongation factor DSIF. MYC recruits SPT5 to promoters of genes and is required for its association with Pol II. The transfer of SPT5 is mediated by CDK7 activity on TFIIE, which evicts it from Pol II and allows SPT5 to bind Pol II. MYC is required for fast and processive transcription elongation, consistent with known functions of SPT5 in yeast. In addition, MYC increases the directionality of promoters by stimulating sense transcription and by suppressing the synthesis of antisense transcripts. The results presented in this thesis suggest that MYC globally controls the productive assembly of Pol II with general elongation factors to form processive elongation complexes in response to growth-factor stimulation of non-tumour cells. However, MYC is found to be overexpressed in many tumours, and is required for their development and progression. In this thesis it was found that, unexpectedly, such overexpression of MYC does not further enhance transcription but rather brings about squelching of SPT5. This reduces the processivity of Pol II on selected set of genes that are known to be repressed by MYC, leading to a decrease in growth-suppressive gene transcription and uncontrolled tumour growth}, language = {en} } @article{KunzBommertKruketal.2020, author = {Kunz, Viktoria and Bommert, Kathryn S. and Kruk, Jessica and Schwinning, Daniel and Chatterjee, Manik and St{\"u}hmer, Thorsten and Bargou, Ralf and Bommert, Kurt}, title = {Targeting of the E3 ubiquitin-protein ligase HUWE1 impairs DNA repair capacity and tumor growth in preclinical multiple myeloma models}, series = {Scientific Reports}, volume = {10}, journal = {Scientific Reports}, doi = {10.1038/s41598-020-75499-3}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-230632}, year = {2020}, abstract = {Experimental evidence suggests that ubiquitin-protein ligases regulate a number of cellular processes involved in tumorigenesis. We analysed the role of the E3 ubiquitin-protein ligase HUWE1 for pathobiology of multiple myeloma (MM), a still incurable blood cancer. mRNA expression analysis indicates an increase in HUWE1 expression levels correlated with advanced stages of myeloma. Pharmacologic as well as RNAi-mediated HUWE1 inhibition caused anti-proliferative effects in MM cell lines in vitro and in an MM1.S xenotransplantation mouse model. Cell cycle analysis upon HUWE1 inhibition revealed decreased S phase cell fractions. Analyses of potential HUWE1-dependent molecular functions did not show involvement in MYC-dependent gene regulation. However, HUWE1 depleted MM cells displayed increased DNA tail length by comet assay, as well as changes in the levels of DNA damage response mediators such as pBRCA1, DNA-polymerase beta, gamma H2AX and Mcl-1. Our finding that HUWE1 might thus be involved in endogenous DNA repair is further supported by strongly enhanced apoptotic effects of the DNA-damaging agent melphalan in HUWE1 depleted cells in vitro and in vivo. These data suggest that HUWE1 might contribute to tumour growth by endogenous repair of DNA, and could therefore potentially be exploitable in future treatment developments.}, language = {en} } @article{EffenbergerBommertKunzetal.2017, author = {Effenberger, Madlen and Bommert, Kathryn S. and Kunz, Viktoria and Kruk, Jessica and Leich, Ellen and Rudelius, Martina and Bargou, Ralf and Bommert, Kurt}, title = {Glutaminase inhibition in multiple myeloma induces apoptosis via MYC degradation}, series = {Oncotarget}, volume = {8}, journal = {Oncotarget}, number = {49}, doi = {10.18632/oncotarget.20691}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-170168}, pages = {85858-85867}, year = {2017}, abstract = {Multiple Myeloma (MM) is an incurable hematological malignancy affecting millions of people worldwide. As in all tumor cells both glucose and more recently glutamine have been identified as important for MM cellular metabolism, however there is some dispute as to the role of glutamine in MM cell survival. Here we show that the small molecule inhibitor compound 968 effectively inhibits glutaminase and that this inhibition induces apoptosis in both human multiple myeloma cell lines (HMCLs) and primary patient material. The HMCL U266 which does not express MYC was insensitive to both glutamine removal and compound 968, but ectopic expression of MYC imparted sensitivity. Finally, we show that glutamine depletion is reflected by rapid loss of MYC protein which is independent of MYC transcription and post translational modifications. However, MYC loss is dependent on proteasomal activity, and this loss was paralleled by an equally rapid induction of apoptosis. These findings are in contrast to those of glucose depletion which largely affected rates of proliferation in HMCLs, but had no effects on either MYC expression or viability. Therefore, inhibition of glutaminolysis is effective at inducing apoptosis and thus serves as a possible therapeutic target in MM.}, language = {en} } @phdthesis{Kettler2019, author = {Kettler, Julia}, title = {Der antiproliferative Effekt des epigenetischen BRD4- Inhibitors JQ1 auf den proliferativen Ph{\"a}notyp humaner kolorektaler Karzinomzellen}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-176418}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2019}, abstract = {Der niedermolekulare Inhibitor JQ1 bindet an der Bromodom{\"a}ne von BRD4, ein auf epigenetischer Ebene agierendes Protein. Der antiproliferative Effekt von JQ1 wurde bisher bei verschiedenen Tumorentit{\"a}ten vor allem des lymphatischen und blutbildenden Systems gezeigt. In dieser Arbeit wurde der antiproliferative Effekt von JQ1 an f{\"u}nf humanen kolorektalen Karzinomzelllinien im Vergleich zu nicht transformierten Kontrollzellen (Fibroblasten) in Normoxie, Hypoxie und in der Langzeitkultur nachgewiesen. Außerdem verringerte JQ1 die Expression von MYC auf Protein- und mRNA-Ebene und steigerte die Transkription des durch MYC negativ regulierten Zielegens p21. Diese Steigerung korrelierte mit einem Zellzyklusarrest in der G0/G1-Phase in vier von f{\"u}nf kolorektalen Karzinomzelllinien.}, subject = {MYC}, language = {de} } @article{LorenzinBenaryBaluapurietal.2016, author = {Lorenzin, Francesca and Benary, Uwe and Baluapuri, Apoorva and Walz, Susanne and Jung, Lisa Anna and von Eyss, Bj{\"o}rn and Kisker, Caroline and Wolf, Jana and Eilers, Martin and Wolf, Elmar}, title = {Different promoter affinities account for specificity in MYC-dependent gene regulation}, series = {eLife}, volume = {5}, journal = {eLife}, doi = {10.7554/eLife.15161}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-162913}, pages = {e15161}, year = {2016}, abstract = {Enhanced expression of the MYC transcription factor is observed in the majority of tumors. Two seemingly conflicting models have been proposed for its function: one proposes that MYC enhances expression of all genes, while the other model suggests gene-specific regulation. Here, we have explored the hypothesis that specific gene expression profiles arise since promoters differ in affinity for MYC and high-affinity promoters are fully occupied by physiological levels of MYC. We determined cellular MYC levels and used RNA- and ChIP-sequencing to correlate promoter occupancy with gene expression at different concentrations of MYC. Mathematical modeling showed that binding affinities for interactions of MYC with DNA and with core promoter-bound factors, such as WDR5, are sufficient to explain promoter occupancies observed in vivo. Importantly, promoter affinity stratifies different biological processes that are regulated by MYC, explaining why tumor-specific MYC levels induce specific gene expression programs and alter defined biological properties of cells.}, language = {en} } @phdthesis{Dejure2018, author = {Dejure, Francesca Romana}, title = {Investigation of the role of MYC as a stress responsive protein}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-158587}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2018}, abstract = {The transcription factor MYC is deregulated in over 70\% of all human tumors and, in its oncogenic form, plays a major role in the cancer metabolic reprogramming, promoting the uptake of nutrients in order to sustain the biosynthetic needs of cancer cells. The research presented in this work aimed to understand if MYC itself is regulated by nutrient availability, focusing on the two major fuels of cancer cells: glucose and glutamine. Initial observations showed that endogenous MYC protein levels strongly depend on the availability of glutamine, but not of glucose. Subsequent analysis highlighted that the mechanism which accounts for the glutamine-mediated regulation of MYC is dependent on the 3´-untranslated region (3´-UTR) of MYC. Enhanced glutamine utilization by tumors has been shown to be directly linked to MYC oncogenic activity and MYC-dependent apoptosis has been observed under glutamine starvation. Such effect has been described in experimental systems which are mainly based on the use of MYC transgenes that do not contain the 3´-UTR. It was observed in the present study that cells are able to survive under glutamine starvation, which leads to cell cycle arrest and not apoptosis, as previously reported. However, enforced expression of a MYC transgene, which lacks the 3´-UTR, strongly increases the percentage of apoptotic cells upon starvation. Evaluation of glutamine-derived metabolites allowed to identify adenosine nucleotides as the specific stimulus responsible for the glutamine-mediated regulation of MYC, in a 3´-UTR-dependent way. Finally, glutamine-dependent MYC-mediated effects on RNA Polymerase II (RNAPII) function were evaluated, since MYC is involved in different steps of global transcriptional regulation. A global loss of RNAPII recruitment at the transcriptional start site results upon glutamine withdrawal. Such effect is overcome by enforced MYC expression under the same condition. This study shows that the 3´UTR of MYC acts as metabolic sensor and that MYC globally regulates the RNAPII function according to the availability of glutamine. The observations presented in this work underline the importance of considering stress-induced mechanisms impinging on the 3´UTR of MYC.}, subject = {Myc}, language = {en} } @phdthesis{Lorenzin2016, author = {Lorenzin, Francesca}, title = {Regulation of transcription by MYC - DNA binding and target genes}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-150766}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2016}, abstract = {MYC is a transcription factor, whose expression is elevated or deregulated in many human cancers (up to 70\%) and is often associated with aggressive and poorly differentiated tumors. Although MYC is extensively studied, discrepancies have emerged about how this transcription factor works. In primary lymphocytes, MYC promotes transcriptional amplification of virtually all genes with an open promoter, whereas in tumor cells MYC regulates specific sets of genes that have significant prognostic value. Furthermore, the set of target genes that distinguish MYC's physiological function from the pathological/oncogenic one, whether it exists or not, has not been fully understood yet. In this study, it could be shown that MYC protein levels within a cell and promoter affinity (determined by E-box presence or interaction with other proteins) of target genes toward MYC are important factors that influence MYC activity. At low levels, MYC can amplify a certain transcriptional program, which includes high affinity binding sites, whereas at high levels MYC leads to the specific up- and down regulation of genes with low affinity. Moreover, the promoter affinity characterizes different sets of target genes which can be distinguished in the physiological or oncogenic MYC signatures. MYC-mediated repression requires higher MYC levels than activation and formation of a complex with MIZ1 is necessary for inhibiting expression of a subset of MYC target genes.}, subject = {MYC}, language = {en} } @article{PeterBultinckMyantetal.2014, author = {Peter, Stefanie and Bultinck, Jennyfer and Myant, Kevin and Jaenicke, Laura A. and Walz, Susanne and M{\"u}ller, Judith and Gmachl, Michael and Treu, Matthias and Boehmelt, Guido and Ade, Casten P. and Schmitz, Werner and Wiegering, Armin and Otto, Christoph and Popov, Nikita and Sansom, Owen and Kraut, Norbert and Eilers, Martin}, title = {H Tumor cell-specific inhibition of MYC function using small molecule inhibitors of the HUWE1 ubiquitin ligase}, series = {EMBO Molecular Medicine}, volume = {6}, journal = {EMBO Molecular Medicine}, number = {12}, issn = {1757-4684}, doi = {10.15252/emmm.201403927}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-118132}, pages = {1525-41}, year = {2014}, abstract = {Deregulated expression of MYC is a driver of colorectal carcinogenesis, necessitating novel strategies to inhibit MYC function. The ubiquitin ligase HUWE1 (HECTH9, ARF-BP1, MULE) associates with both MYC and the MYC-associated protein MIZ1. We show here that HUWE1 is required for growth of colorectal cancer cells in culture and in orthotopic xenograft models. Using high-throughput screening, we identify small molecule inhibitors of HUWE1, which inhibit MYC-dependent transactivation in colorectal cancer cells, but not in stem and normal colon epithelial cells. Inhibition of HUWE1 stabilizes MIZ1. MIZ1 globally accumulates on MYC target genes and contributes to repression of MYC-activated target genes upon HUWE1 inhibition. Our data show that transcriptional activation by MYC in colon cancer cells requires the continuous degradation of MIZ1 and identify a novel principle that allows for inhibition of MYC function in tumor cells.}, language = {en} } @article{BerendzenWeisteWankeetal.2012, author = {Berendzen, Kenneth W. and Weiste, Christoph and Wanke, Dierk and Kilian, Joachim and Harter, Klaus and Dr{\"o}ge-Laser, Wolfgang}, title = {Bioinformatic cis-element analyses performed in Arabidopsis and rice disclose bZIP- and MYB-related binding sites as potential AuxRE-coupling elements in auxin-mediated transcription}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-75138}, year = {2012}, abstract = {Background: In higher plants, a diverse array of developmental and growth-related processes is regulated by the plant hormone auxin. Recent publications have proposed that besides the well-characterized Auxin Response Factors (ARFs) that bind Auxin Response Elements (AuxREs), also members of the bZIP- and MYB-transcription factor (TF) families participate in transcriptional control of auxin-regulated genes via bZIP Response Elements (ZREs) or Myb Response Elements (MREs), respectively. Results: Applying a novel bioinformatic algorithm, we demonstrate on a genome-wide scale that singular motifs or composite modules of AuxREs, ZREs, MREs but also of MYC2 related elements are significantly enriched in promoters of auxin-inducible genes. Despite considerable, species-specific differences in the genome structure in terms of the GC content, this enrichment is generally conserved in dicot (Arabidopsis thaliana) and monocot (Oryza sativa) model plants. Moreover, an enrichment of defined composite modules has been observed in selected auxin-related gene families. Consistently, a bipartite module, which encompasses a bZIP-associated G-box Related Element (GRE) and an AuxRE motif, has been found to be highly enriched. Making use of transient reporter studies in protoplasts, these findings were experimentally confirmed, demonstrating that GREs functionally interact with AuxREs in regulating auxin-mediated transcription. Conclusions: Using genome-wide bioinformatic analyses, evolutionary conserved motifs have been defined which potentially function as AuxRE-dependent coupling elements to establish auxin-specific expression patterns. Based on these findings, experimental approaches can be designed to broaden our understanding of combinatorial, auxin-controlled gene regulation.}, subject = {Arabidopsis}, language = {en} } @phdthesis{CardosoeCastro2012, author = {Cardoso e Castro, In{\^e}s Sofia}, title = {Epigenetic switch induced by MYC in Non-Small-Cell Lung Cancer}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-76713}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2012}, abstract = {Non-Small-Cell Lung Cancer (NSCLC) is the most frequent human lung cancer and a major cause of death due to its high rate of metastasis1. These facts emphasize the urgent need for the investigation of new targets for anti-metastatic therapy. Up to now a number of genes and gene products have been identified that positively or negatively affect the probability of established human tumor cell lines to metastasize2. Previously, together with the group of Professor Ulf Rapp, we have described the first conditional mouse model for metastasis of NSCLC and identified a gene, c-MYC, that is able to orchestrate all steps of this process. We could identify potential markers for detection of metastasis and highlighted GATA4, which is exclusively expressed during lung development, as a target for future therapeutic intervention2. However, the mechanism underlying this metastatic conversion remained to be identified, and was therefore the focus of the present work. Here, GATA4 is identified as a MYC target in the development of metastasis and epigenetic alterations at the GATA4 promoter level are shown after MYC expression in NSCLC in vivo and in vitro. Such alterations include site-specific demethylation that accompanies the displacement of the MYC-associated zinc finger protein (MAZ) from the GATA4 promoter, which leads to GATA4 expression. Histone modification analysis of the GATA4 promoter revealed a switch from repressive histone marks to active histone marks after MYC binding, which corresponds to active GATA4 expression. This work identifies a novel epigenetic mechanism by which MYC activates GATA4 leading to metastasis in NSCLC, suggesting novel potential targets for the development of anti-metastatic therapy.}, subject = {Nicht-kleinzelliges Bronchialkarzinom}, language = {en} }