Project description:Homologous vertebrate tissues express a highly conserved set of transcribed genes; paradoxically, expression of tRNAs that are required to translate mRNAs into proteins have been reported to be divergent. To resolve this paradox, we mapped the genome-wide occupancy of pol III in primary tissues isolated from six mammals. We confirmed that the specific tRNA genes bound by pol III, as well as the extent and stability of binding, can vary substantially among mammalian tissues, and we discovered that this divergence is far greater between species. We combined pol III occupancy from genomically discrete tRNA loci into collective binding into isoacceptor classes and then into amino acid-based isotype classes, and at each step we found increasing conservation. At the level of amino acid isotypes, pol III binding is almost invariant among all the tissues and species profiled. Thus, the basal transcriptional machinery is constrained collectively in its synthesis of functional tRNA isotypes, despite rapid divergence of polymerase binding to specific tRNA genes. Part of experiment series: RNA-Seq E-MTAB-424, ChIP-Seq E-MTAB-957
Project description:Tumor cells have an increased need for amino acids. Mammalian cells cannot synthesize essential amino acids; they must obtain these amino acids via specific transporters. Glutamine, though a non-essential amino acid, is critical for tumor cells (glutamine addiction). Entry of amino acids into tumor cells is enhanced by upregulation of specific transporters. If the transporters that are specifically induced in tumor cells are identified, blockade of the induced transporters would constitute a logical strategy for cancer treatment. The transporter SLC6A14 is unique and transports all essential amino acids as well as glutamine and is expressed only at low levels in normal tissues, but induced in colon cancer and in ER+ breast cancer. We have now established the potential of this transporter as a drug target for breast cancer treatment using genetic and pharmacologic approaches. We then examined the progression of breast cancer in Polyoma middle T antigen (Py-MT) Tg mouse on Slc6a14+/+ and Slc6a14-/- background using microarray analysis. We have used three Affy-chips for each tumor sample (Group 1: WT/PyMT; Group 2: Slc6a14-KO/PyMT). Three biological replicates were used for each group.
Project description:The Aryl hydrocarbon Receptor (AhR) is a transcription factor well known in vertebrate to play an essential role as xenobiotic sensor. On the contrary, no ligand has been identified to date for invertebrate AhR. In some model organisms such as D. melanogaster and C. elegans, AhR orthologs have physiological functions and their inability to bind prototypical ligands of vertebrate AhR such as tetrachlorodibenzo-p-dioxin (TCDD) suggests that the detoxification role of the receptor could be an adaptation acquired during evolution. To better understand the physiological roles of AhR, we studied AhR-1, the C. elegans ortholog and performed transcriptomic and metabolomic analysis respectively in neuronal cells expressing AhR-1 and in whole animals. Next, we designed a reporter system in order to investigate if the transcriptional activity of AhR-1 could be modulated. Cos-7 cells were transfected with AhR-1, its dimerization partner AhA-1 (C. elegans ARNT ortholog) and a Firefly luciferase gene under the control of the human cytochrome P450 1A1 promotor. The luciferase bioluminescence measurement allows the identification of C. elegans AhR-1 modulators. Transcriptional profiling in neurons expressing AhR-1 revealed 95 genes down-regulated, and 76 genes up-regulated in AhR-1 KO animals. These genes are associated with nervous system function (depleted) and fatty acid process, oxidative phosphorylation and glycolysis (enriched). Metabolomic profiling results indicate a role for AhR-1 in regulating several endogenous metabolic pathways: amino-acid metabolism, carbohydrate metabolism as well as fatty acid metabolism Then, with the COS-7 in vitro screening model, we identified positive and negative modulators such as bacterial, dietary or environmental compounds. Considering C. elegans environment, these results could be used to highlight the role of invertebrate AhR and identified new features in vertebrate AhR.