Project description:Enhancers are fundamental to gene regulation. Post-translational modifications by the small ubiquitin-like modifiers (SUMO) modify chromatin regulation enzymes, including histone acetylases and deacetylases. However, it remains unclear whether SUMOylation regulates enhancer marks, acetylation at the 27th lysine residue of the histone H3 protein (H3K27Ac). We hypothesize that SUMOylation regulates H3K27Ac. To test this hypothesis, we performed genome-wide ChIP-seq analyses. We discovered that knockdown (KD) of the SUMO activating enzyme catalytic subunit UBA2 reduced H3K27Ac at most enhancers. Bioinformatic analysis revealed that TFAP2C-binding sites are enriched in enhancers whose H3K27Ac was reduced by UBA2 KD. ChIP-seq analysis in combination with molecular biological methods showed that TFAP2C binding to enhancers increased upon UBA2 KD or inhibition of SUMOylation by a small molecule SUMOylation inhibitor. However, this is not due to the SUMOylation of TFAP2C itself. Proteomics analysis of TFAP2C interactome on the chromatin identified histone deacetylation (HDAC) machinery. TFAP2C KD reduced HDAC binding to chromatin and increased H3K27Ac marks at enhancer regions, suggesting that TFAP2C is involved in recruiting HDAC. Taken together, our findings provide important insights into regulation of enhancer marks by SUMOylation.
Project description:Extensive functional analyses have demonstrated that the pituitary homeodomain transcription factor Pitx1 plays a critical role in specifying hindlimb morphology in vertebrates. However, much less is known regarding the target genes and cis-regulatory elements through which Pitx1 acts. Earlier studies suggested that the hindlimb transcription factors Tbx4, HoxC10, and HoxC11 might be transcriptional targets of Pitx1, but definitive evidence for direct regulatory interactions has been lacking. Using ChIP-Seq on embryonic mouse hindlimbs, we have pinpointed the genome-wide location of Pitx1 binding sites during mouse hindlimb development and identified potential gene targets for Pitx1. We determined that Pitx1 binding is significantly enriched near genes involved in limb morphogenesis, including Tbx4, HoxC10, and HoxC11. Notably, Pitx1 is bound to the previously identified HLEA and HLEB hindlimb enhancers of the Tbx4 gene and to a newly identified Tbx2 hindlimb enhancer. Moreover, Pitx1 binding is significantly enriched on hindlimb relative to forelimb-specific cis-regulatory features that are differentially marked by H3K27ac. However, our analysis revealed that Pitx1 also strongly associates with many functionally verified limb enhancers that exhibit similar levels of activity in the embryonic mesenchyme of forelimbs and hindlimbs. We speculate that Pitx1 influences hindlimb morphology both through the activation of hindlimb specific enhancers as well as through the hindlimb-specific modulation of enhancers that are active in both sets of limbs. Embryonic hindlimb buds from 4 ICR mouse samples were used.
Project description:Melanomas are heterogeneous and adopt multiple transcriptional states that can confer an invasive phenotype and resistance to therapy. Little is known about the epigenetic drivers of these cell states, limiting our ability to regulate melanoma heterogeneity and tumor progression. Here we identify stress-induced HDAC8 activity as the driver of a transcriptional state that increased the formation of melanoma brain metastases (MBM). Exposure of melanocytes and melanoma cells to multiple different stresses led to HDAC8 activation, a switch to a gene expression signature associated with a neural crest-stem cell like state (NCSC) and the adoption of an amoeboid, invasive phenotype. This cell state enhanced the survival of melanoma cells under shear stress conditions and increased the formation of metastases in the brain. ATAC-Seq and ChIP-Seq analysis showed HDAC8 to alter chromatin structure by increasing H3K27ac and accessibility at c-Jun binding sites without changing global histone acetylation. The increased accessibility of Jun binding sites was paralleled by decreased H3K27ac and accessibility at MITF binding sites and loss of melanoma-lineage gene expression. Mass spectrometry-based acetylomics demonstrated that HDAC8 deacetylated the histone acetyltransferase (HAT) EP300 leading to its enzymatic inactivation. This, in turn, led to an increased binding of EP300 to Jun-transcriptional sites and decreased binding to MITF-transcriptional sites. Increased expression of EP300 decreased invasion and increased the sensitivity of melanoma cells to multiple stresses while inhibition of EP300 function increased invasion, resistance to stress and the development of MBM. We identified HDAC8 as a novel mediator of transcriptional co-factor inactivation and chromatin accessibility that increases MBM development.
Project description:ChIP-seq analysis of H3K27ac profile was carried out to exploit the differences in chromatin activation status between Primary and Metastatic Melanoma.
Project description:Using microcell-mediated chromosome transfer (MMCT) into the mouse melanoma cell line, B16F10, we have previously found that human chromosome 5 carries a gene, or genes, that can negatively regulate TERT expression. To identify the gene responsible for the regulation of TERT transcription, we performed cDNA microarray analysis using parental B16F10 cells, telomerase negative B16F10 microcell hybrids with a human chromosome 5 (B16F10MH5), and its revertant clones (MH5R) with reactivated telomerase. Here we report the identification of PITX1, whose restoration leads to the downregulation of mouse tert (mtert) transcription, as a TERT suppressor gene. Additionally, both human TERT (hTERT) and mouse TERT (mtert) promoter activity can be suppressed by PITX1. We showed that three and one binding sites, respectively, within the hTERT and mtert promoters that express a unique conserved region are responsible for the transcriptional activation of TERT. Furthermore, we showed that PITX1 binds to the TERT promoter both in vitro and in vivo. Thus, PITX1 suppresses TERT transcription through direct binding to the TERT promoter, which ultimately regulates telomerase activity. We transferred intact human chromosome 5 into mouse melanoma B16F10 cells by microcell fusion. The microcell hybrids (MH5) exhibited suppression of telomerase, we also obtained revertant clones (MH5R) in which telomerase is reactivated. To identify the differentially expressed genes on human chromosome 5, we performed expression microarray analysis using these two clones and parental B16F10 cells.
Project description:In this report, we generated eight matched pairs of vemurafenib sensitive/resistant melanoma lines and subjected these to concurrent RNA-seq and H3K27Ac ChIP-seq analysis. Globally, we identified two classes of epigenetic profiles that correlate with resistance. Class 1 resistance involves fewer RNA expression alterations accompanied by fewer enhancer mark changes with H3K27Ac. Class 2 resistance shows widespread alterations in transcription and enhancer profiles, which converge on EMT and hypoxia-related pathways. We also observed significant and dynamic changes in super-enhancers that underpin these transcriptomic patterns. We subsequently verified the 2-class structure in pre-BRAFi and post-relapse human melanoma specimens. Our findings reveal a broad and underappreciated spectrum of epigenetic plasticity during acquired BRAFi resistance.
Project description:In this report, we generated eight matched pairs of vemurafenib sensitive/resistant melanoma lines and subjected these to concurrent RNA-seq and H3K27Ac ChIP-seq analysis. Globally, we identified two classes of epigenetic profiles that correlate with resistance. Class 1 resistance involves fewer RNA expression alterations accompanied by fewer enhancer mark changes with H3K27Ac. Class 2 resistance shows widespread alterations in transcription and enhancer profiles, which converge on EMT and hypoxia-related pathways. We also observed significant and dynamic changes in super-enhancers that underpin these transcriptomic patterns. We subsequently verified the 2-class structure in pre-BRAFi and post-relapse human melanoma specimens. Our findings reveal a broad and underappreciated spectrum of epigenetic plasticity during acquired BRAFi resistance.
Project description:A 122-epigenetic gene signature distinguished low- versus high-risk early stage melanomas. We sought to validate the signature, examined clinical correlates in a cohort of primary melanomas of the skin, and studied the underlying transcriptomic aberrations and changes in chromatin in cell lines representing these two groups. H3K27Ac ChipSeq profiles of primary human melanoma cell lines (n=4) as well as corresponding input samples were generated by deep sequencing using Illumina NextSeq500. Purpose: The goals of this study are to identify H3K27Ac differential peak expression between two groups of melanoma cell lines (Epgn1 and Epgn3) and relate this data to RNASeq. Methods: H3K27Ac ChipSeq was performed on 4 melanoma cell lines by deep sequencing 75bp single end reads using Illumina NextSeq500. Reads were aligned and counts called using____. The sequence reads that passed quality filters were analyzed. Results: Using an optimized data analysis workflow, we mapped about 40 million reads per Chip sample and 60 million reads per input sample to the human genome (build _____). Conclusions: Our study allowed us to identify differentially expressed peaks between two classes of melanoma cell lines and relate this information to differential gene expression. Further in vitro and in vivo assays using some of the candidate genes identified will allow us to more fully understand primary melanoma progression.
Project description:Extensive functional analyses have demonstrated that the pituitary homeodomain transcription factor Pitx1 plays a critical role in specifying hindlimb morphology in vertebrates. However, much less is known regarding the target genes and cis-regulatory elements through which Pitx1 acts. Earlier studies suggested that the hindlimb transcription factors Tbx4, HoxC10, and HoxC11 might be transcriptional targets of Pitx1, but definitive evidence for direct regulatory interactions has been lacking. Using ChIP-Seq on embryonic mouse hindlimbs, we have pinpointed the genome-wide location of Pitx1 binding sites during mouse hindlimb development and identified potential gene targets for Pitx1. We determined that Pitx1 binding is significantly enriched near genes involved in limb morphogenesis, including Tbx4, HoxC10, and HoxC11. Notably, Pitx1 is bound to the previously identified HLEA and HLEB hindlimb enhancers of the Tbx4 gene and to a newly identified Tbx2 hindlimb enhancer. Moreover, Pitx1 binding is significantly enriched on hindlimb relative to forelimb-specific cis-regulatory features that are differentially marked by H3K27ac. However, our analysis revealed that Pitx1 also strongly associates with many functionally verified limb enhancers that exhibit similar levels of activity in the embryonic mesenchyme of forelimbs and hindlimbs. We speculate that Pitx1 influences hindlimb morphology both through the activation of hindlimb specific enhancers as well as through the hindlimb-specific modulation of enhancers that are active in both sets of limbs.