Project description:Posttranslational histone modifications play important roles in regulating chromatin structure and function. Histone H2B ubiquitination and deubiquitination have been implicated in transcriptional regulation, but the function of H2B deubiquitination is not well defined, particularly in higher eukaryotes. Here we report the purification of USP49 as a histone H2B specific deubiquitinase and demonstrate that H2B deubiquitination by USP49 is required for efficient co-transcriptional splicing of a large set of exons. USP49 forms a complex with RVB1 and SUG1, and specifically deubiquitinates histone H2B in vitro and in vivo. USP49 knockdown results in small changes in gene expression, but affects the abundance of over 9,000 isoforms. Exons down-regulated in USP49 knockdown cells show both elevated levels of alternative splicing and a general decrease in splicing efficiency. Importantly, USP49 is relatively enriched at this set of exons. USP49 knockdown increased uH2B levels at these exons as well as upstream 3’ and downstream 5’ intronic splicing elements. Change in H2B ubiquitination level, as modulated by USP49, regulates U1A and U2B association with chromatin and binding to nascent pre-mRNA. Although H3 levels are relatively stable after USP49 depletion, H2B levels at these exons are dramatically increased, suggesting that uH2B may enhance nucleosome stability. Therefore, this study identifies USP49 as a histone H2B specific deubiquitinase and uncovers a critical role for H2B deubiquitination in co-transcriptional pre-mRNA processing events. Examination of histone H2B ubiquitination in wild type and USP49 knockdown cells [ChIP-Seq]
Project description:Posttranslational histone modifications play important roles in regulating chromatin structure and function. Histone H2B ubiquitination and deubiquitination have been implicated in transcriptional regulation, but the function of H2B deubiquitination is not well defined, particularly in higher eukaryotes. Here we report the purification of USP49 as a histone H2B specific deubiquitinase and demonstrate that H2B deubiquitination by USP49 is required for efficient co-transcriptional splicing of a large set of exons. USP49 forms a complex with RVB1 and SUG1, and specifically deubiquitinates histone H2B in vitro and in vivo. USP49 knockdown results in small changes in gene expression, but affects the abundance of over 9,000 isoforms. Exons down-regulated in USP49 knockdown cells show both elevated levels of alternative splicing and a general decrease in splicing efficiency. Importantly, USP49 is relatively enriched at this set of exons. USP49 knockdown increased uH2B levels at these exons as well as upstream 3’ and downstream 5’ intronic splicing elements. Change in H2B ubiquitination level, as modulated by USP49, regulates U1A and U2B association with chromatin and binding to nascent pre-mRNA. Although H3 levels are relatively stable after USP49 depletion, H2B levels at these exons are dramatically increased, suggesting that uH2B may enhance nucleosome stability. Therefore, this study identifies USP49 as a histone H2B specific deubiquitinase and uncovers a critical role for H2B deubiquitination in co-transcriptional pre-mRNA processing events. Examination of gene expression in wild type and USP49 knockdown cells [RNA-Seq]
Project description:This work details the first global mass spectrometric analysis of histone H2B variants as cells undergo arsenic-mediated epithelial to mesenchymal transition.
Project description:Doxycycline-inducible YAP1 S127A-driven rhabdomyosarcoma (RMS) tumors, control skeletal muscle and regressed tumors following YAP1 normalization by doxycycline withdrawal were compared to determine the YAP1-regulated gene expression profile relevant to RMS formation. To characterize the role of YAP1 in embryonal RMS at the molecular level and identify a gene signature for YAP1 activity readout, we compared the gene expression profiles of our YAP1-driven ERMS with control donor skeletal muscle (SKM) and doxycycline-withdrawn regressing tumors by microarray (doxycycline withdrawal for 3 or 6 days; OFF3 and OFF6, respectively). We next extracted a list of genes regulated by YAP1 in our YAP1-driven ERMS tumors (TUM) versus the 3 other conditions: skeletal muscle control (SKM), Doxycycline-withdrawn 3 days (OFF3) and 6 days (OFF6). The overlap between the 3 lists identified a subset of 633 common upregulated genes, named the YAP1-ERMS_UP signature, as well as 249 common downregulated genes, termed the YAP1-ERMS_DOWN signature. Proliferative pathways and transcriptional targets of E2F factors were highlighted in the YAP1-ERMS_UP genes, while muscle differentiation and trancriptional targets of myogenic factors Myod1 and Mef2 were highlighted in the YAP1-ERMS_DOWN genes. Tumor regression conditions (OFF3 days; OFF6 days) as well as control muscle (CTL) were compared with tumors at day 0 of doxycycline withdrawal (TUM). 3 samples for each conditions were used.
Project description:Imp9 is the primary importin for shuttling H2A-H2B from the cytoplasm to the nucleus. It employs an unusual mechanism where the binding of RanGTP is insufficient to release H2A-H2B. The resulting stable RanGTP•Imp9•H2A-H2B complex gains nucleosome assembly activity with H2A-H2B able to be deposited into an assembling nucleosome in vitro. Using hydrogen-deuterium exchange coupled with mass spectrometry (HDX), we show that Imp9 stabilizes H2A-H2B beyond the direct binding site, like other histone chaperones. HDX also shows that binding of RanGTP releases H2A-H2B contacts at Imp9 HEAT repeats 4-5, but not 18-19. DNA- and histone-binding surfaces of H2A-H2B are exposed in the ternary complex, facilitating nucleosome assembly. We also reveal that RanGTP has a weaker affinity for Imp9 when H2A-H2B is bound. Imp9 thus provides a connection between the nuclear import of H2A-H2B and its deposition into chromatin.
Project description:During early vertebrate development, signals from a special region of the embryo, the organizer, can re-direct the fate of non-neural ectoderm cells to form a complete, patterned nervous system. This is called neural induction and has generally been imagined as a single signaling event, causing a switch of fate. Here we undertake a comprehensive analysis, in very fine time-course, of the events following exposure of ectoderm to the organizer. Using transcriptomics and epigenomics we generate a Gene Regulatory Network comprising 175 transcriptional regulators and 5,614 predicted interactions between them, with fine temporal dynamics from initial exposure to the signals to expression of mature neural plate markers. Using in situ hybridization, single-cell RNA-sequencing and reporter assays we show that neural induction by a grafted organizer mimics normal neural plate development. The study is accompanied by a comprehensive resource including information about conservation of the predicted enhancers in different vertebrate systems.
Project description:The purpose of the experiment is to study the expression profiles variations upon the expression of the wild type isoform of LKB1 (STK11) in human lung carcinoma A459 cells. These cells are KRAS mutated and null for STK11. Cells were previously infected with the lentiviral construct pLenti-rtTA2-IRES-H2B-GFP doxycycline-inducible plasmid (obtained from S. Tenbaum, HG Palmer’s Lab Vall d´Hebron Institute of Oncology, VHIO) containing the human STK11wild type cDNA.
Project description:Polycomb repressive complex-1 (PRC1) is essential for the epigenetic regulation of gene expression. SCML2 is a mammalian homolog of Drosophila SCM, a Polycomb-group protein that associates with PRC1. Here, we show that SCML2A, an SCML2 isoform tightly associated to chromatin, contributes to PRC1 localization and also directly enforces repression of certain Polycomb target genes. SCML2A binds to PRC1 via its SPM domain and interacts with ncRNAs through a novel RNA-binding region (RBR). Targeting of SCML2A to chromatin involves the coordinated action of the MBT domains, RNA binding, and interaction with PRC1 through the SPM domain. Deletion of the RBR reduces the occupancy of SCML2A at target genes and overexpression of a mutant SCML2A lacking the RBR causes defects in PRC1 recruitment. These observations point to a role for ncRNAs in regulating SCML2 function and suggest that SCML2 participates in the epigenetic control of transcription directly and in cooperation with PRC1. This is the ChIP-seq part of the study
Project description:Formation of the complex vertebrate nervous system begins when pluripotent cells of the early embryo are directed to acquire a neural fate. Although cell intrinsic controls play an important role in this process, the molecular nature of this regulation is not well defined. Here we assessed the role for Geminin, a nuclear protein expressed in embryonic cells, in neural fate acquisition from mouse embryonic stem (ES) cells. While Geminin knockdown does not affect the ability of ES cells to maintain or exit pluripotency, we found that it significantly impairs their ability to acquire a neural fate. Conversely, Geminin overexpression promotes neural gene expression, even in the presence of growth factor signaling that antagonizes neural transcriptional responses. These data demonstrate that Geminin’s activity contributes to mammalian neural cell fate acquisition. We investigated the mechanistic basis of this phenomenon and found that Geminin maintains a hyperacetylated and open chromatin conformation at neural genes. Interestingly, recombinant Geminin protein also rapidly alters chromatin acetylation and accessibility even when Geminin is combined with nuclear extract and chromatin in vitro. These findings define a novel activity for Geminin in regulation of chromatin structure. Together, these data support a role for Geminin as a cell intrinsic regulator of neural fate acquisition that promotes expression of neural genes by regulating chromatin accessibility and histone acetylation. Mouse embryonic stem cells were differentiated for two days in N2B27 medium, with or without Doxycycline-inducible shRNAmir knockdown of Geminin and compared by microarray. Three independent experiments were conducted, using two different mouse embryonic stem cell lines for Doxycycline-inducible knockdown of Geminin. The two ES lines express unique shRNAmir sequences targeting Geminin (shRNAmir #9 and #11) to control for off-target effects.
Project description:Mitochondrial protein import in the parasitic protozoan Trypanosoma brucei is mediated by the atypical outer membrane translocase, ATOM. It consists of seven subunits including ATOM69, the import receptor for hydrophobic proteins. Ablation of ATOM69, but not of any other subunit, triggers a unique quality control pathway resulting in the proteasomal degradation of non-imported mitochondrial proteins. The process requires a protein of unknown function, an E3 ubiquitin ligase and the ubiquitin-like protein (TbUbL1), which all are recruited to the mitochondrion upon ATOM69 depletion. TbUbL1 is a nuclear protein, a fraction of which is released to the cytosol upon triggering of the pathway. Nuclear release is essential since cytosolic TbUbL1 can bind mislocalized mitochondrial proteins and likely transfers them to the proteasome. Mitochondrial quality control has previously been studied in yeast and metazoans. Finding such a pathway in the highly diverged trypanosomes suggests such pathways are an obligate feature of all mitochondria.