Project description:TP53 is mutated in 50% of all cancers, and is often functionally compromised in cancers where it is not mutated. We demonstrate that the pro-tumorigenic/metastatic Six1 homeoprotein decreases p53 levels through a mechanism that does not involve the negative regulator of p53, MDM2. Instead, Six1 regulates p53 via a dual mechanism involving upregulation of microRNA-27a and downregulation of the ribosomal protein L26 (RPL26), a positive regulator of p53 translation. Mutation analysis confirms that RPL26, whose expression inversely correlates with Six1 expression in numerous tumor types, inhibits miR-27a binding to the p53 3’UTR and prevents microRNA-mediated translational inhibition of p53. Thus, through simultaneous downregulation of RPL26 and upregulation of miR-27a, Six1 efficiently lowers p53 levels despite regulation of p53 at the level of the proteasome. Consequently, Six1 overexpression, which is observed in numerous tumor types, leads to dramatic resistance to nutlins, as well as other therapies targeting the p53-MDM2 interaction.
Project description:TP53 is mutated in 50% of all cancers, and is often functionally compromised in cancers where it is not mutated. We demonstrate that the pro-tumorigenic/metastatic Six1 homeoprotein decreases p53 levels through a mechanism that does not involve the negative regulator of p53, MDM2. Instead, Six1 regulates p53 via a dual mechanism involving upregulation of microRNA-27a and downregulation of the ribosomal protein L26 (RPL26), a positive regulator of p53 translation. Mutation analysis confirms that RPL26, whose expression inversely correlates with Six1 expression in numerous tumor types, inhibits miR-27a binding to the p53 3’UTR and prevents microRNA-mediated translational inhibition of p53. Thus, through simultaneous downregulation of RPL26 and upregulation of miR-27a, Six1 efficiently lowers p53 levels despite regulation of p53 at the level of the proteasome. Consequently, Six1 overexpression, which is observed in numerous tumor types, leads to dramatic resistance to nutlins, as well as other therapies targeting the p53-MDM2 interaction.
Project description:MicroRNAs are well known to mediate translational repression and mRNA degradation in the cytoplasm. Various microRNAs have also been detected in membrane-compartmentalized organelles, but the functional significance has remained elusive. Here we report that miR-1, a microRNA specifically induced during myogenesis, efficiently enters the mitochondria where it unexpectedly stimulates, rather than represses, the translation of specific mitochondrial genome-encoded transcripts. We show that this positive effect requires specific miR:mRNA base-pairing and Ago2, but not its functional partner GW182, which is excluded from the mitochondria. We provide evidence for the direct action of Ago2 in mitochondrial translation by Ago2 CrossLinking ImmunoPrecipitation coupled with sequencing (CLIP-seq), functional rescue with mitochondria-targeted Ago2, and selective inhibition of the microRNA machinery in the cytoplasm. These findings unveil a positive function of microRNA in mitochondrial translation and suggest a highly coordinated myogenic program via miR-1 mediated translational stimulation in the mitochondria and repression in the cytoplasm. Examination of miRNA's regulation function in mitochondria in C2C12 myoblasts cells and myotubes cells with CLIP-seq (Ago2).
Project description:We have recently confirmed miR-27a-3p as a crucial regulator of human adipogenesis (Wu H, Pula T, Tews D, Amri E-Z, Debatin K-M, Wabitsch M, Fischer-Posovszky P, Roos J. microRNA-27a-3p but Not -5p Is a Crucial Mediator of Human Adipogenesis. Cells. 2021; 10(11):3205. https://doi.org/10.3390/cells10113205 ). MiR-27a-5p did not impair human adipogenesis. However, since several publications state that miR-27a ist also a crucial regulator of UCP1, we were interested if miR-27a-3p or miR-27a-5p regulatas UCP1 and other thermogenesis related genes. We found a strong regulation of UCP1 with functional relevance for the cellular metabolism by miR-27a-5p.To asesse the mRNA gene expression pattern, mRNA sequencing was performed.
Project description:MicroRNAs are well known to mediate translational repression and mRNA degradation in the cytoplasm. Various microRNAs have also been detected in membrane-compartmentalized organelles, but the functional significance has remained elusive. Here we report that miR-1, a microRNA specifically induced during myogenesis, efficiently enters the mitochondria where it unexpectedly stimulates, rather than represses, the translation of specific mitochondrial genome-encoded transcripts. We show that this positive effect requires specific miR:mRNA base-pairing and Ago2, but not its functional partner GW182, which is excluded from the mitochondria. We provide evidence for the direct action of Ago2 in mitochondrial translation by Ago2 CrossLinking ImmunoPrecipitation coupled with sequencing (CLIP-seq), functional rescue with mitochondria-targeted Ago2, and selective inhibition of the microRNA machinery in the cytoplasm. These findings unveil a positive function of microRNA in mitochondrial translation and suggest a highly coordinated myogenic program via miR-1 mediated translational stimulation in the mitochondria and repression in the cytoplasm.
Project description:The knock down of T-cell intracellular antigen (TIA) proteins enhances the acquisition of aberrant cellular phenotypes promoting uncontrolled cell and tumor growth. Hereby, we report that inducible expression of either TIA1 or TIAR in human embryonic kidney (HEK293) cells represses cell proliferation. Mechanistically, the sustained expression of either TIA1 or TIAR protein abolishes endogenous TIA1/TIAR protein expression via regulating splicing of their own pre-mRNAs. This event is concomitant with cell cycle arrest and cell death by apoptosis. Based on genome-wide analysis of the transcript expression patterns in HuR-, TIA1- or TIAR-expressing HEK293 cells, we found regulatory links among the up-regulation on a select subset of p53 pathway genes involved in G1/S cell-cycle and apoptosis control. Finally, nude mice injected with TIA1- or TIAR-expressing HEK293 cells decrease, and even abolishing, the growth of tumor xenografts relative to control cells. Collectively, these observations show that TIA proteins can function as tumor suppressor genes. Two independent biological replicates were performed per sample type. Agilent SurePrint G3 Human Gene Expression 8x60K v2 array were used in all cases (single-channel hybridizations)
Project description:Rap1GAP is a critical tumor suppressor gene that is down-regulated in multiple aggressive cancers such as head and neck squamous cell carcinoma, melanoma and pancreatic cancer. However, the mechanistic basis of rap1GAP down-regulation in cancers is poorly understood. By employing an integrative approach, we demonstrate polycomb-mediated repression of rap1GAP that involves EZH2, a histone methyltransferase in head and neck cancers. We further concomitant down-regulation of rap1GAP in head and neck cancers. EZH2 represses rap1GAP by facilitating the trimethylation of H3K27, a mark of gene repression, and also hypermethylation of rap1GAP promoter. These results provide a conceptual framework involving a microRNA-oncogene-tumor suppressor axis to understand head and neck cancer progression. OSCC3-siRNA Non-Targeting Vs. siRNA EZH2 with dye-swap, HOK-Adeno CMV Vs. Adeno EZH2.
Project description:The homeodomain transcription factor SIX1 plays a critical role in embryogenesis, is not expressed in normal adult tissue, but is expressed in many malignancies, including cervical cancer. SIX1 drives the progression of HPV16-immortalized human keratinocytes (HKc/HPV16) toward malignancy: HKc/HPV16 express high levels of SIX1 mRNA and protein; overexpression of SIX1 in HKc/HPV16 produces pre-malignant, differentiation-resistant lines (HKc/DR); SIX1 overexpression in HKc/DR induces tumorigenicity. In this paper, we explore the consequences of inhibition of SIX1 expression in premalignant HKc/DR. Only partial inhibition of SIX1 expression could be obtained in HKc/DR by RNA interference. Decreased SIX1 expression (up to 80%) in HKc/DR resulted in slower proliferation, decreased HPV16-E6/E7 mRNA levels, and increased p53 protein levels. Gene expression changes induced in HKc/DR by anti-SIX1 shRNA were indicative of mesenchymal-epithelial transition (EMT) and changes in TGF-beta signaling. We conclude that HPV16-transformed cells depend on SIX1 for survival, continuous HPV16 E6/E7 gene expression and EMT.
Project description:E4F1 is a ubiquitously expressed zinc-finger protein of the Gli-Kruppel family that was first identified, more than 30 years ago, as a cellular target of the adenoviral oncoprotein E1A13S (Ad type V), required for transcriptional regulation of adenoviral genes. In order to identify the p53-independent program controlled by E4F1, we performed microarray analyses in p53 KO and p53 KO; Ha-RasV12-transformed mouse embryonic fibroblasts (MEFs) in wild type and E4F1-inactivated cells.