Project description:HIF-1 regulated VEGF expression were upregulated in reponse to ischemic injury. However, the VEGF mRNA level were increased in the early stage but decreased in the late stage of myocardial infarction. We found that activities of HIF-1 binding to the HRE sites were possiblely responsible for the differential expression of VEGF. The HIF-1 binding activities were regulated by copper. After ischemic injury, copper concentrations were decreased in the infarct myocardium in the late stage of myocardial infarction, which might reduce VEGF expression through insufficient HIF-1 binding to HRE sites.
Project description:Copper (Cu) regulates hypoxia-inducible factor-1 (HIF-1) transcription activity by affecting the selectivity of HIF-1α targeting to the promoters of the affected genes. Here, we made an effort to provide a comprehensive understanding of Cu regulation of the selectivity of HIF-1α targeting across genome. We used tetraethylenepentamine (TEPA), a Cu selective chelator, to reduce Cu content in the cells. In hypoxia, we conducted chromatin immunoprecipitation combined with massively parallel DNA sequencing (ChIP-seq) to globally map the binding sites of HIF-1α, Pol Ⅱ (RNA polymeraseⅡ) and histone H3K27ac. We also performed RNA-sequencing (RNA-seq) in EA.hy926 cells under hypoxia (1% O2) with or without Cu depression to determine the profile of mRNA expression. Our analyses identified 3197 HIF-1α binding sites under hypoxia. Cu depression by TEPA reduced 1820 binding sites from the 3197, but induced additional 274 new binding sites. We analyzed these binding sites in the promoter and putative enhancer regions, coupled with their mRNA expression profiles, and found 281 Cu-dependent and 10 Cu-independent HIF-1α target genes. We found that the core bases “GGAA” and “TTCC” constituted the critical motifs for the binding sites of Cu-dependent genes. This study thus revealed that Cu, by affecting the binding of HIF-1α to the critical motifs in the promoter and putative enhancer regions of HIF-1 regulated genes, leads to the selectivity of HIF-1 regulated expression of Cu-dependent genes.
Project description:Copper (Cu) regulates hypoxia-inducible factor-1 (HIF-1) transcription activity by affecting the selectivity of HIF-1α targeting to the promoters of the affected genes. Here, we made an effort to provide a comprehensive understanding of Cu regulation of the selectivity of HIF-1α targeting across genome. We used tetraethylenepentamine (TEPA), a Cu selective chelator, to reduce Cu content in the cells. In hypoxia, we conducted chromatin immunoprecipitation combined with massively parallel DNA sequencing (ChIP-seq) to globally map the binding sites of HIF-1α, Pol Ⅱ (RNA polymeraseⅡ) and histone H3K27ac. We also performed RNA-sequencing (RNA-seq) in EA.hy926 cells under hypoxia (1% O2) with or without Cu depression to determine the profile of mRNA expression. Our analyses identified 3197 HIF-1α binding sites under hypoxia. Cu depression by TEPA reduced 1820 binding sites from the 3197, but induced additional 274 new binding sites. We analyzed these binding sites in the promoter and putative enhancer regions, coupled with their mRNA expression profiles, and found 281 Cu-dependent and 10 Cu-independent HIF-1α target genes. We found that the core bases “GGAA” and “TTCC” constituted the critical motifs for the binding sites of Cu-dependent genes. This study thus revealed that Cu, by affecting the binding of HIF-1α to the critical motifs in the promoter and putative enhancer regions of HIF-1 regulated genes, leads to the selectivity of HIF-1 regulated expression of Cu-dependent genes.
Project description:Mutational inactivation of VHL is the earliest genetic event in the majority of ccRCCs, leading to activation of the HIF-1α and HIF-2α transcription factors. While correlative studies of human ccRCCs and functional studies using human ccRCC cell lines have implicated HIF-1α as an inhibitor and HIF-2α as a promoter of aggressive tumour behaviours, their roles in tumour onset have not been functionally addressed. Using an autochthonous ccRCC model, we show genetically that Hif1a is necessary for tumour formation whereas Hif2a deletion has only minor effects on tumour initiation and growth. Both HIF-1α and HIF-2α are necessary for the clear cell phenotype. Transcriptomic and proteomic analyses revealed that HIF-1α regulates glycolysis while HIF-2α regulates genes associated with lipoprotein metabolism, ribosome biogenesis and E2F and MYC transcriptional activities. Deficiency of HIF-2α increased CD8+ T cell infiltration and activation. These studies reveal different functions of HIF-1α and HIF-2α in ccRCC. SIGNIFICANCE The roles of HIF-1α and HIF-2α in ccRCC pathogenesis remain unclear. Using a mouse genetic approach we show that HIF-1α but not HIF-2α is important for tumour formation, contrary to predictions from studies of human ccRCC. We show that HIF-1α and HIF-2α transcriptionally regulate different aspects of metabolism and identify HIF-2α as a suppressor of immune cell infiltration and activation.
Project description:Intestinal epithelia exist in a uniquely dynamic oxygen tension microenvironment. Adaptive responses to hypoxia in mammalian cells are regulated largely by hypoxia inducible factor (HIF) transcriptional complexes. Functional HIF exists as an obligate alpha/beta heterodimer, comprising both a constitutive subunit (HIF-1beta), and an oxygen-labile regulatory (alpha) component. To date, three regulatory subunits have been identified, namely HIF-1alpha, HIF-2alpha, and HIF-3alpha, with the highest level of sequence homology conserved between HIF-1alpha and HIF-2alpha. Despite their concurrent expression in intestinal epithelial cells, HIF-1 and HIF-2 play non-redundant roles in the regulation of an overlapping but distinct set of gene targets. In this study, we performed ChIP-on-chip analysis of chromatin isolated from hypoxic intestinal epithelia to delineate HIF-1 and HIF-2 specific loci. Comparison of HIF-1alpha ChIP-chip and HIF-2alpha ChIP-chip to map HIF-1- and HIF-2-specific gene targets across the genome.