Project description:Cells transiently adapt to hypoxia by globally decreasing protein translation. However, specific proteins needed to respond to hypoxia evade this translational repression. The mechanisms of this phenomenon remain unclear. We screened for and identified small molecules that selectively decrease HIF-2a translation in an mTOR independent manner, by enhancing the binding of Iron Regulatory Protein 1 (IRP1) to a recently reported Iron-Responsive Element (IRE) within the 5â-untranslated region (UTR) of the HIF-2a message. Knocking down the expression of IRP1 by shRNA abolished the effect of the compounds. Hypoxia de-represses HIF-2a translation by disrupting the IRP1- HIF-2a IRE interaction. Thus, this chemical genetic analysis describes a molecular mechanism by which translation of the HIF-2a message is maintained during conditions of cellular hypoxia through inhibition of IRP-1 dependent repression. It also provides the chemical tools for studying this phenomenon. Experiment Overall Design: 3 replicate samples of 786-O human Clear Cell Renal Carcinoma cells untreated, mock treated with DMSO or treated with either of 4 HIF-2a inhibitor compounds identified by chemical genetic screening.
Project description:Cells transiently adapt to hypoxia by globally decreasing protein translation. However, specific proteins needed to respond to hypoxia evade this translational repression. The mechanisms of this phenomenon remain unclear. We screened for and identified small molecules that selectively decrease HIF-2a translation in an mTOR independent manner, by enhancing the binding of Iron Regulatory Protein 1 (IRP1) to a recently reported Iron-Responsive Element (IRE) within the 5’-untranslated region (UTR) of the HIF-2a message. Knocking down the expression of IRP1 by shRNA abolished the effect of the compounds. Hypoxia de-represses HIF-2a translation by disrupting the IRP1- HIF-2a IRE interaction. Thus, this chemical genetic analysis describes a molecular mechanism by which translation of the HIF-2a message is maintained during conditions of cellular hypoxia through inhibition of IRP-1 dependent repression. It also provides the chemical tools for studying this phenomenon.
Project description:The hypoxia inducible factor (HIF) system orchestrates cellular responses to hypoxia in animals. HIF is an /-heterodimeric transcription factor that regulates the expression of hundreds of genes in a context dependent manner. A hypoxia-sensing component of the HIF system involves oxygen-dependent catalysis by the HIF hydroxylases; in humans there are three HIF prolyl hydroxylases (PHD1-3) and an asparaginyl hydroxylase (FIH). PHD catalysis regulates HIF levels and FIH catalysis regulates HIF activity. How differences in HIF hydroxylation status relate to variations in the induction of HIF target gene transcription is unknown. We report studies using small molecule inhibitors of the HIF hydroxylases to investigate the extent to which HIF target gene upregulation is induced by reduced PHD catalysis. The results reveal substantial differences in the role of prolyl- and asparaginyl-hydroxylation in regulating hypoxia responsive genes in cells. Selective PHD inhibitors with different structural scaffolds behave similarly. However, under the tested conditions, a broad-spectrum 2OG dioxygenase inhibitor is a better mimic of the transcriptional response to hypoxia than the selective PHD inhibitors, consistent with an important role for FIH in the hypoxic transcriptional response. Indeed, combined application of selective PHD and FIH inhibitors resulted in transcriptional induction of a subset of genes that were not fully responsive to PHD inhibition alone. Thus, for the therapeutic regulation of HIF target genes, it is important to consider both PHD and FIH activity, and in the case of some sets of target genes, simultaneous inhibition of the PHDs and FIH catalysis may be preferable.
Project description:The hypoxia inducible factor (HIF) system orchestrates cellular responses to hypoxia in animals. HIF is an α/β-heterodimeric transcription factor that regulates the expression of hundreds of genes in a context dependent manner. A hypoxia-sensing component of the HIF system involves oxygen-dependent catalysis by the HIF hydroxylases; in humans there are three HIF prolyl hydroxylases (PHD1-3) and an asparaginyl hydroxylase (FIH). PHD catalysis regulates HIFα levels and FIH catalysis regulates HIF activity. How differences in HIFα hydroxylation status relate to variations in the induction of HIF target gene transcription is unknown. We report studies using small molecule inhibitors of the HIF hydroxylases to investigate the extent to which HIF target gene upregulation is induced by reduced PHD catalysis. The results reveal substantial differences in the role of prolyl- and asparaginyl-hydroxylation in regulating hypoxia responsive genes in cells. Selective PHD inhibitors with different structural scaffolds behave similarly. However, under the tested conditions, a broad-spectrum 2OG dioxygenase inhibitor is a better mimic of the transcriptional response to hypoxia than the selective PHD inhibitors, consistent with an important role for FIH in the hypoxic transcriptional response. Indeed, combined application of selective PHD and FIH inhibitors resulted in transcriptional induction of a subset of genes that were not fully responsive to PHD inhibition alone. Thus, for the therapeutic regulation of HIF target genes, it is important to consider both PHD and FIH activity, and in the case of some sets of target genes, simultaneous inhibition of the PHDs and FIH catalysis may be preferable.
Project description:Comparison of CoV 3'UTR cis-acting element interactome to link the cis-acting element to coronavirus replication by LC-MS/MS. The study is performed by in vitro-transcribed RNA followed by RNA-protein pull-down assay. In addition, the concluded results are decided by comparison between the biological processes derived from analysis of interactome and the replication efficiency.
Project description:Comparison of CoV 3'UTR cis-acting element interactome to link the cis-acting element to coronavirus replication by LC-MS/MS. The study is performed by in vitro-transcribed RNA followed by RNA-protein pull-down assay. In addition, the concluded results are decided by comparison between the biological processes derived from analysis of interactome and the replication efficiency.
Project description:The transcription factor HIF-2a play an important role in the tumor progress, the aim is to explore the target genes of HIF-2a in liver cancer cell line. Chromatin immunoprecipitation (ChIP) of HIF-2a together with chromatin profiling by ChIP-on-chip analysis demonstrated that HIF-2a directly activates many target genes. Analyze the target genes in a liver cancer cell line MHCC97H
Project description:The transcription factor HIF-2a play an important role in the tumor progress, the aim is to explore the target genes of HIF-2a in liver cancer cell line. Chromatin immunoprecipitation (ChIP) of HIF-2a together with chromatin profiling by ChIP-on-chip analysis demonstrated that HIF-2a directly activates many target genes.
Project description:Nuclear speckles are dynamic nuclear bodies characterized by high local concentrations of RNA binding proteins and specific non-coding RNAs. Although the contents of speckles suggest multifaceted roles in regulating chromatin dynamics and gene expression, the overarching biological function(s) of nuclear speckles remain enigmatic. In this study, we investigate speckle compositional variation in human cancer, finding two main speckle compositional states based on RNA expression of speckle-resident proteins. One cancer speckle state was more similar to normal adjacent tissues, while the other was dissimilar from normal tissue, and thus considered an aberrant cancer speckle state. We link the aberrant speckle state to altered speckle positioning within the nucleus, to elevation of the TREX RNA export complex, and to worse patient outcomes in clear cell renal cell carcinoma (ccRCC). ccRCC is typified by hyperactivation of the HIF-2a transcription factor, and we demonstrate that HIF-2a drives physical association of a select subset of its target genes with nuclear speckles depending on HIF-2a's two speckle targeting motifs (STMs) defined in this study. STMs are highly enriched among transcription factors, suggesting that DNA-speckle targeting may be a general mechanism of gene regulation and providing a resource of candidate speckle-targeting factors. Via integration of tissue culture functional studies with tumor genomic and imaging analysis, we show that HIF-2a gene regulatory programs are impacted by speckle compositional state and by abrogation of speckle targeting abilities of HIF-2a. These findings suggest that, in ccRCC, a key biological function of nuclear speckles is to modulate expression of a specific subset of HIF-2a-regulated target genes that, in turn, influence patient outcomes. Beyond ccRCC, tumor speckle compositional states broadly correlate with altered functional pathways and expression of speckle-associated gene neighborhoods, exposing a general link between nuclear speckles and gene expression dysregulation in human cancer.