Project description:The Polycomb group (PcG) and Trithorax group (TrxG) of proteins are required for stable and heritable maintenance of repressed and active gene expression states. Their antagonistic function on gene control, repression for PcG and activity for TrxG, is mediated by binding to chromatin and subsequent epigenetic modification of target loci. Despite our broad knowledge about composition and enzymatic activities of the protein complexes involved, our understanding still lacks important mechanistic detail and a comprehensive view on target genes. In this study, we use an extensive data set of ChIP-seq, RNA-seq, and genome-wide detection of transcription start sites (TSSs) to identify and analyze thousands of binding sites for the PcG proteins and Trithorax from a Drosophila S2 cell line. In addition to finding a preference for stalled promoter regions of annotated genes, we uncover many intergenic PcG-binding sites coinciding with non-annotated transcription start sites. Interestingly, this set includes previously unknown promoters for primary transcripts of microRNA genes, thereby expanding the scope of Polycomb control to non-coding RNAs essential for development, apoptosis and growth. Chromatin from S2 cells was immunoprecipitated using antibodies against Pc, Ph, Psc, Trx-C or H3K4me3. In parallel, we isolated RNA from S2 cells and generated global gene expression profiles by RNA-seq. We also surveyed the Drosophila genome for yet non-annotated transcription start sites (TSSs) using a newly adapted protocol for Illumina sequencing (termed 5M-bM-^@M-^Y-MACE) with RNA isolated from S2 cells and embryos.
Project description:The Polycomb group (PcG) and Trithorax group (TrxG) of proteins are required for stable and heritable maintenance of repressed and active gene expression states. Their antagonistic function on gene control, repression for PcG and activity for TrxG, is mediated by binding to chromatin and subsequent epigenetic modification of target loci. Despite our broad knowledge about composition and enzymatic activities of the protein complexes involved, our understanding still lacks important mechanistic detail and a comprehensive view on target genes. In this study, we use an extensive data set of ChIP-seq, RNA-seq, and genome-wide detection of transcription start sites (TSSs) to identify and analyze thousands of binding sites for the PcG proteins and Trithorax from a Drosophila S2 cell line. In addition to finding a preference for stalled promoter regions of annotated genes, we uncover many intergenic PcG-binding sites coinciding with non-annotated transcription start sites. Interestingly, this set includes previously unknown promoters for primary transcripts of microRNA genes, thereby expanding the scope of Polycomb control to non-coding RNAs essential for development, apoptosis and growth.
Project description:Understanding the transcriptional regulatory circuitry responsible for pluripotency and self-renewal in embryonic stem (ES) cells is fundamental to understanding human development and realizing the therapeutic potential of these cells. The transcription factor Oct4 and the chromatin-modifying Polycomb complex, key regulators of ES cell pluripotency and self-renewal, contribute to positive and negative control of a known set of protein-coding genes. MicroRNAs (miRNAs), non-coding transcripts that participate in post-transcriptional gene regulation are also important for normal pluripotency and self-renewal in ES cells, but there has been no systematic investigation of how miRNA expression is controlled by transcriptional regulators of ES cell identity. Here we identify promoters for miRNAs in the human and mouse genomes and describe the subset of these genes that are under the control of Oct4 and Polycomb in ES cells. We find that the majority of miRNAs that are uniquely or preferentially expressed in ES cells are bound by and dependent on Oct4. Oct4 also occupies a set of miRNA genes that are co-occupied by the Polycomb Group protein, Suz12. These miRNAs, repressed in ES cells, are later expressed in differentiated cells in a highly tissue-specific fashion, suggesting that they may contribute to cell-fate determinations. These data reveal how the core transcriptional regulatory circuitry of ES cells controls the miRNA expression program that contributes to pluripotency and self-renewal.
Project description:Drosophila melanogaster is a well-studied genetic model organism with several large-scale transcriptome resources. Here we investigate 7,952 proteins during the fly life cycle from embryo to adult and also provide a high-resolution temporal time course proteome of 5,458 proteins during embryogenesis. We use our large scale data set to compare transcript/protein expression, uncovering examples of extreme differences between mRNA and protein abundance. In the embryogenesis proteome, the time delay in protein synthesis after transcript expression was determined. For some proteins, including the transcription factor lola, we monitor isoform specific expression levels during early fly development. Furthermore, we obtained firm evidence of 268 small proteins, which are hard to predict by bioinformatics. We observe peptides originating from non-coding regions of the genome and identified Cyp9f3psi as a protein-coding gene. As a powerful resource to the community, we additionally created an interactive web interface (http://www.butterlab.org) advancing the access to our data.
Project description:Recent studies have revealed a myriad of non-coding transcripts in different organisms. For instances, the presence of short bidirectional transcripts is a hallmark of active promoters in mammals, while upstream non-coding transcripts can be detected at most expressed genes in conditions where the RNA degradation machinery is inhibited. Here, we used RNA-seq with very high sequencing depth to characterize strand specific transcripts from primary mouse tissues. We found that a substantial fraction of gene promoters sustain expression of long non-coding antisense transcripts. These transcripts have an average size of 6 kb, have features of mature transcripts, but remain associated with the chromatin. We named this new class of non-coding RNAs Long Upstream Antisense Transcripts (LUAT). Strikingly, the LUAT and coding gene pairs are usually co-regulated, with the associated genes often/generally coding for transcriptional regulators functioning during development and cell differentiation. Indeed, these bidirectional promoters share several characteristic of developmental gene promoters, including large CpG islands and high degree of conservation, and display symetrical GC skews. Finally, we found that bidirectional promoters have enlarged platforms of Pol II initiation, associated with an intensified rate of early transcriptional elongation. We concluded that promoters of developmental regulators are characterized by a specialized mechanism of Pol II transcription, whereby Pol II poising is directly coupled to relaxed bidirectional transcription. H3K79me2 ChIP in CD4+,CD8+ double positive thymocytes from C57BL/6 mice was studied, using Illumina sequencer
Project description:Recent studies have revealed a myriad of non-coding transcripts in different organisms. For instances, the presence of short bidirectional transcripts is a hallmark of active promoters in mammals, while upstream non-coding transcripts can be detected at most expressed genes in conditions where the RNA degradation machinery is inhibited. Here, we used RNA-seq with very high sequencing depth to characterize strand-specific transcripts from primary mouse tissues. We found that a substantial fraction of gene promoters sustain expression of long non-coding antisense transcripts. These transcripts have an average size of 6 kb, have features of mature transcripts, but remain associated with the chromatin. We named this new class of non-coding RNAs Long Upstream Antisense Transcripts (LUAT). Strikingly, the LUAT and coding gene pairs are usually co-regulated, with the associated genes often/generally coding for transcriptional regulators functioning during development and cell differentiation. Indeed, these bidirectional promoters share several characteristics of developmental gene promoters, including large CpG islands and high degree of conservation, and display symetrical GC skews. Finally, we found that bidirectional promoters have enlarged platforms of Pol II initiation, associated with an intensified rate of early transcriptional elongation. We concluded that promoters of developmental regulators are characterized by a specialized mechanism of Pol II transcription, whereby Pol II poising is directly coupled to relaxed bidirectional transcription. Runx1 ChIP-seq in CD4+,CD8+ double-positive (DP) mice thymocytes using single-end sequencing on AB SOLiD Systems.