Project description:PcG and TrxG are important epigenetic regulators of genome expression. Here we have determined genomic distributions of PC, E(Z), H3K27me3, TRX, ASH1, RNA Pol II, H3K4me3, H3K27ac in cultured Drosophila ML-DmBG3-c2 cells by hybridization of ChIP products with tiling microarrays.
Project description:We used ChIP on chip assays to determine the genome wide distribution of a large set of PcG and trxG proteins, their associated histone marks and four candidate DNA-binding factors for PcG protein recruitment.
Project description:We used ChIP on chip assays to determine the genome wide distribution of a large set of PcG and trxG proteins, their associated histone marks and four candidate DNA-binding factors for PcG protein recruitment.
Project description:PcG and TrxG are important epigenetic regulators of genome expression. Here we have determined genomic distributions of PC, E(Z), H3K27me3, TRX, ASH1, RNA Pol II, H3K4me3, H3K27ac in cultured Drosophila ML-DmD23-c4 cells by hybridization of ChIP products with tiling microarrays
Project description:PcG and TrxG are important epigenetic regulators of genome expression. Here we have determined genomic distributions of TRX, ASH1, RNA Pol II, H3K4me3, H3K27ac, H3K9ac in cultured Drosophila Sg4 cells by hybridization of ChIP products with tiling microarrays.
Project description:Background: The question of how cells re-establish gene expression states after cell division is still poorly understood. Genetic and molecular analyses have indicated that Trithorax group (TrxG) proteins are critical for the long-term maintenance of active gene expression states in many organisms. A generally accepted model suggests that TrxG proteins contribute to maintenance of transcription by protecting genes from inappropriate Polycomb group (PcG)-mediated silencing, instead of directly promoting transcription. Results: Here we report a physical and functional interaction in Drosophila between two members of the TrxG, the histone methyltransferase ASH1 and the bromodomain and extraterminal family protein FSH. We investigated this interface at the genome level, uncovering a widespread colocalization of both proteins at promoters and PcG-bound intergenic elements. Our integrative analysis of chromatin maps and gene expression profiles revealed that the observed ASH1-FSH binding pattern at promoters is a hallmark of active genes. Inhibition of FSH-binding to chromatin resulted in global down-regulation of transcription. In addition, we found that genes displaying marks of robust PcG-mediated repression also have ASH1 and FSH bound to their promoters. Conclusions: Our data strongly favor a global coactivator function of ASH1 and FSH during transcription, as opposed to the notion that TrxG proteins impede inappropriate PcG-mediated silencing, but are dispensable elsewhere. Instead, our results suggest that PcG repression needs to overcome the transcription-promoting function of ASH1 and FSH in order to silence genes. Refer to individual Series
Project description:We report an ex vivo kinome-wide RNAi screen in Drosophila aimed to identify cell signaling genes that facilitate trxG to counteract PcG mediated repression. From the list of trxG candidates, Ballchen (BALL), a histone kinase, known to phosphorylate histone H2A at threonine 119 (H2AT119p), was characterized as a trxG regulator. BALL co-localizes with Trithorax on chromatin and depletion of BALL results in increased H2AK118 ubiquitination, a histone mark central to PcG mediated gene silencing. Moreover, analysis of genome-wide binding profile of BALL shows an overlap with 85% known binding sites of TRX across the genome. Both BALL and TRX are highly enriched at actively transcribed genes, which also correlate with presence of H3K4me3 and H3K27ac. We propose that BALL mediated signal positively contributes to the maintenance of gene activation by trxG by counteracting the repressive effect of PcG.
Project description:The antagonistic POLYCOMB (PcG) REPRESSIVE COMPLEX 2 (PRC2) and trithorax (trxG) chromatin machineries play a major role in orchestrating gene expression during the development of multicellular eukaryotes. These complexes are well known for depositing and maintaining the repressive H3K27me3 and activating H3K4me3 marks, respectively. However, the mechanisms that govern the switch between these functions remains elusive, especially in plants, whose lifelong, flexible development relies heavily on this process. Here we demonstrate that the plant specific ULTRAPETALA1 (ULT1) protein, previously reported as a trxG factor that antagonizes the PRC2 enzymatic subunit CURLY LEAF (CLF), also exhibits a repressive function, increasing H3K27me3 levels at over a thousand genes. We discovered a physical interaction between ULT1 and PRC2 components, particularly the SWINGER (SWN) enzymatic subunit. We further show that ULT1 significantly enhances PRC2SWN enzymatic activity in vitro, corroborating our epigenomic and developmental genetic data that reveal different ULT1 activity depending on the catalytic subunit of the PRC2 complex. This study provides new insights into the relative activities of CLF and SWN and introduces a novel mechanistic framework for a chromatin switch mediated by a bivalent trxG/PcG factor.
