Project description:<p>Non-coding elements in our genomes that play critical roles in complex disease are frequently marked by highly unstable RNA species. Sequencing nascent RNAs attached to an actively transcribing RNA polymerase complex can identify unstable RNAs, including those templated from gene-distal enhancers (eRNAs). However, nascent RNA sequencing techniques remain challenging to apply in some cell lines and especially to intact tissues, limiting broad applications in fields such as cancer genomics and personalized medicine. Here we report the development of chromatin run-on and sequencing (ChRO-seq), a novel run-on technology that maps the location of RNA polymerase using virtually any frozen tissue sample, including samples with degraded RNA that are intractable to conventional RNA-seq. We used ChRO-seq to develop the first maps of nascent transcription in 23 human glioblastoma (GBM) brain tumors and patient derived xenografts. Remarkably, >90,000 distal enhancers discovered using the signature of eRNA biogenesis within primary GBMs closely resemble those found in the normal human brain, and diverge substantially from GBM cell models. Despite extensive overall similarity, 12% of enhancers in each GBM distinguish normal and malignant brain tissue. These enhancers drive regulatory programs similar to the developing nervous system and are enriched for transcription factor binding sites that specify a stem-like cell fate. These results demonstrate that GBMs largely retain the enhancer landscape associated with their tissue of origin, but selectively adopt regulatory programs that are responsible for driving stem-like cell properties. We also identified enhancers and their associated transcription factors that regulate genes characteristic of each known GBM subtype, and discovered a core group of transcription factors that control the expression of genes associated with clinical outcomes. This study uncovers new insights into the molecular etiology of GBM and introduces ChRO-seq which can now be used to map regulatory programs contributing to a variety of complex diseases.</p>
Project description:Transcriptional coregulators and transcription factors (TFs) contain intrinsically disordered regions (IDRs) that are critical for their partitioning and function in gene regulation. Canonically, IDRs drive coregulator-TF association by directly promoting multivalent protein-protein interactions. Using a chemical genetic approach, we report an unexpected mechanism by which the IDR of the corepressor LSD1 excludes TF association, acting as a dynamic conformational switch that tunes repression of active cis-regulatory elements. Hydrogen-deuterium exchange shows that the LSD1 IDR interconverts between transient open and closed conformational states, the latter of which inhibits partitioning of the proteins structured domains with TF hubs. This autoinhibitory switch controls leukemic differentiation by modulating repression of active cis-regulatory elements bound by LSD1 and master hematopoietic TFs. Together, these studies unveil that the dynamic crosstalk between opposing structured and unstructured regions is an alternative paradigm by which disordered regions can shape coregulator-transcription factor interactions to control cis-regulatory landscapes and cell fate.
Project description:Transcription termination pathways mitigate the detrimental consequences of unscheduled promiscuous initiation occurring at hundreds of thousands of genomic cis-regulatory elements. The Restrictor complex, composed of the Pol II-interacting protein WDR82 and the RNA-binding protein ZC3H4, suppresses processive transcription at thousands of extragenic sites in mammalian genomes. Restrictor-driven termination does not involve nascent RNA cleavage and its interplay with other termination machineries is unclear. Here we show that efficient termination at Restrictor-controlled extragenic transcription units involves the recruitment of the protein phosphatase 1 (PP1) regulatory subunit PNUTS, a negative regulator of the Spt5 elongation factor, and Symplekin, a protein associated with RNA cleavage complexes but also involved in cleavage-independent and phosphatase-dependent termination of non-coding RNAs in yeast. PNUTS and Symplekin act synergistically with, but independently from Restrictor to dampen processive extragenic transcription. Moreover, the presence of limiting nuclear levels of Symplekin imposes a competition for its recruitment among multiple transcription termination machineries, resulting in mutual regulatory interactions. Hence, by synergizing with Restrictor, Symplekin and PNUTS enable efficient termination of processive, long-range extragenic transcription.
Project description:- transcription factor interferon regulatory factor 4 (IRF4) = crucial transcription factor for different immune cells, incl pro-inflammatory Th17 and anti-inflammatory Treg cells
- IRF4 is essential for the cell differentiation and fate determination
- however molecular mechanisms of IRF4-mediated gene expression in fully differentiated Th17/Treg cells are still not fully understood
- integration of data derived from affinity-purification and full mass spectrometry-based proteome analysis with chromatin immune precipitation sequencing (ChIP-Seq)
- characterization of proteins generally involved in the T cell development as well as subtype-specific differentiation and identification of novel, yet uncharted IRF4 interactors
Project description:Transcription factors (TFs) bind specific sequences in promoter-proximal and distal DNA elements in order to regulate gene transcription. RNA is transcribed from both promoter-proximal and distal DNA elements, and some DNA-binding TFs have also been shown to bind RNA. These obsevations led us to postulate that RNA transcribed from regulatory elements contributes to stable TF occupancy at these regulatory elements. We show here that the ubiquitously expressed TF YY1 binds to both proximal and distal regulatory elements and to the RNA species associated with these elements near active genes in embryonic stem cells. Inhibition of transcription from these elements reduces YY1 occupancy. In contrast, tethering of RNA species near YY1 DNA binding sites enhances YY1 occupancy. We propose that RNA acts as trap to maintain certain TFs at active enhancer and promoter-proximal regulatory elements. Thus, transcriptional control generally involves a positive feedback loop, where YY1 and other TFs stimulate local transcription, and newly transcribed nascent RNA reinforces local TF occupancy. This model helps explain why TFs occupy only the small fraction of their consensus motifs in the mammalian genome where transcription is detected. Affinity purification (ChIP-Seq) for YY1 in mouse embryonic stem cells treated with transcription-affecting compounds
Project description:The human genome shares a remarkable amount of genomic sequence with our closest living primate relatives. Researchers have long sought to understand what regions of the genome are responsible for unique species-specific traits. Previous studies have shown that many genes are differentially expressed between species, but the regulatory elements contributing to these differences are largely unknown. Here we report a genome-wide comparison of active gene regulatory elements in human, chimpanzee, and macaque, and we identify hundreds of regulatory elements that have been gained or lost in the human or chimpanzee genomes since their evolutionary divergence. These elements contain evidence of natural selection and correlate with species-specific changes in gene expression. Polymorphic DNA bases in transcription factor motifs that we found in these regulatory elements may be responsible for the varied biological functions across species. This study directly links phenotypic and transcriptional differences between species with changes in chromatin structure. One biological replicate was analyzed for each of the 15 primate samples using DNase-seq.