Project description:Hypoxia-Inducible Factor 1 (HIF-1) plays a key role in cellular adaptation to hypoxia. To better understand the determinants of HIF-1 binding and transactivation, we used ChIP-chip and gene expression profiling to define the relationship between the epigenetic landscape, sites of HIF-1 binding, and genes transactivated by hypoxia in two cell lines, HepG2 hepatoma cell line and U87 glioma cell line.
Project description:The RNA polymerase II (POLII) driven transcription cycle is tightly regulated at distinct checkpoints through cyclin dependent kinases (CDKs) and their cognate Cyclins. The molecular events underpinning transcriptional elongation and processivity and CDK-Cyclins involved remain poorly understood. Using CRISPR-CAS9 homology-directed-repair we generated analog-sensitive-kinase variants of CDK12 and CDK13 to probe their individual and shared biological and molecular roles. Single inhibition of CDK12 or CDK13 induced transcriptional responses associated with DNA-damage and cellular growth signaling pathways respectively, with minimal effects on cell viability. In contrast, dual-kinase inhibition potently induced cell death, which was associated with extensive genome-wide transcriptional changes including wide-spread use of alternative 3’ polyadenylation sites. At the molecular level dual-kinase inhibition resulted in the loss of POLII CTD phosphorylation and greatly reduced POLII elongation rates and processivity. These data define significant redundancy between CDK12 and CDK13, and identify both as fundamental regulators of global POLII processivity and transcription elongation.
Project description:Binding of Polycomb repressive complex 2 (PRC2) and chromatin composition of the inactive X (Xi) before, during and after X chromosome inactivation reveal that spreading is driven by a combination of Xi-specific strong and moderate Ezh2 sites. Sequence context of these sites shows a moderate enrichment of SINEs and simple repeats. The general pattern of Ezh2 and H3K27me3 distribution over the chromosome reflect a graded concentration originating from strong Ezh2 sites, around which moderate sites are clustered, suggesting a hierarchy of Ezh2 sites govern spreading. ChIP-seq of Ezh2 and H3K27me3 as well as the three active marks H3K4me3, H3K36me3 and RNA-POLII-serine5 phosphorylation (RNA-polII-S5P) in female cell lines: undifferentiated embryonic stem (ES) cells (d0), differentiating ES cells (d7) and a transformed embryonic fibroblast cell line (MEF).
Project description:HIF-1 is an important transcription factor for immune responses to bacterial infection. We wanted to analyze the HIF-1 dependent gene expression upon S. aureus infection and analyzed the gene expression of HepG2 nt and HepG2 HIF-1-/- cells four hours upon infection using affymetrix human gene 1.0 st. gene arrays. triplicates of HepG2 nt and HepG2 HIF-1-/- cells were infected with S. aureus 8325-4 (4 h, MOI: 20), triplicates of uninfected cells were used as control
Project description:The PAF complex (Paf1C) has been shown to regulate chromatin modifications, gene transcription, and PolII elongation. Here, we provide the first genome-wide analysis of chromatin occupancy by the entire PAF complex in mammalian cells. We show that Paf1C is recruited not only to promoters and gene bodies, but also to regions downstream of cleavage/polyadenylation (pA) sites at 3’ ends, a profile that sharply contrasted with the yeast complex. Remarkably, our studies identified novel, subunit-specific links between Paf1C and regulation of alternative cleavage and polyadenylation (APA) and upstream antisense transcription. Moreover, we found that depletion of Paf1C subunits also resulted in the accumulation of RNA polymerase II (PolII) over gene bodies, which coincided with APA. Depletion of specific Paf1C subunits leads to global loss of histone H2B ubiquitylation, but surprisingly, there is little impact of Paf1C depletion on other histone modifications, including the tri-methylation of histone H3 on lysines 4 and 36 (H3K4me3 and H3K36me3), previously associated with this complex. Our results provide surprising differences with yeast, while unifying observations that link Paf1C with PolII elongation and RNA processing, and suggest that Paf1C could play a role in protecting transcripts from premature cleavage by preventing PolII accumulation at TSS-proximal pA 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.