The PRC1 protein RING1B contributes to Ewing sarcoma tumorigenesis by repressing the NaV1.6 sodium channel and modulating the NF-kB pathway, independently of the fusion oncoprotein.
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ABSTRACT: Ewing sarcoma (ES) is an aggressive tumor molecularly defined by reciprocal translocations of EWSR1 to an ETS transcription factor. The functions of EZH2 and BMI1, two proteins of the Polycomb group (PcG) of epigenetic repressors, have been previously shown to mediate specific features in EWSR1/ETS-transformed cells. Here we have characterized the expression and function of RING1B, a PcG protein with unique abilities, in ES. RING1B is highly and universally expressed in primary ES tumors. In contrast to EZH2, RING1B expression is independent of both the oncogene and of differentiation agents. RING1B depletion affects heme biosynthesis and hematopoiesis but does not result in a widespread alteration in ES differentiation. Among the unique set of genes regulated upon RING1B depletion, FGF14 and SCN8A, interacting components of the NaV1.6 channel, are two of the most up-regulated genes. Control of FGF14 and SCN8A in ES is specific of RING1B and functionally relevant. The signaling pathway most significantly modulated by RING1B is NF-κB. Indeed, RING1B depletion results in enhanced p105/p50 expression, which specifically sensitizes ES cells to apoptosis by FGFR/SHP2/STAT3 blockade. In conclusion, we show that RING1B is pivotal in ES cells, independently of the fusion oncogene, likely reflecting essential functional traits of the cell-of-origin. 10 samples were analyzed: A4573 transduced with control shRNA; A4573 transduced with shRING1B; A673 transduced with control shRNA; A673 transduced with shRING1B; SK-ES-1 transduced with control shRNA; SK-ES-1 transduced with shRING1B; TC71 transduced with control shRNA; TC71 transduced with shRING1B; A673 transduced with shBMI1; TC71 transduced with shBMI1
Project description:Ewing sarcoma (ES) is an aggressive tumor molecularly defined by reciprocal translocations of EWSR1 to an ETS transcription factor. The functions of EZH2 and BMI1, two proteins of the Polycomb group (PcG) of epigenetic repressors, have been previously shown to mediate specific features in EWSR1/ETS-transformed cells. Here we have characterized the expression and function of RING1B, a PcG protein with unique abilities, in ES. RING1B is highly and universally expressed in primary ES tumors. In contrast to EZH2, RING1B expression is independent of both the oncogene and of differentiation agents. RING1B depletion affects heme biosynthesis and hematopoiesis but does not result in a widespread alteration in ES differentiation. Among the unique set of genes regulated upon RING1B depletion, FGF14 and SCN8A, interacting components of the NaV1.6 channel, are two of the most up-regulated genes. Control of FGF14 and SCN8A in ES is specific of RING1B and functionally relevant. The signaling pathway most significantly modulated by RING1B is NF-κB. Indeed, RING1B depletion results in enhanced p105/p50 expression, which specifically sensitizes ES cells to apoptosis by FGFR/SHP2/STAT3 blockade. In conclusion, we show that RING1B is pivotal in ES cells, independently of the fusion oncogene, likely reflecting essential functional traits of the cell-of-origin.
Project description:EWSR1-FLI1 genome reprogramming through remodeling of enhancers is determinant for Ewing sarcoma (ES) tumorigenesis. We describe a non-canonical function of RING1B, a PRC1 subunit highly expressed in primary ES tumors, co-localizing genome wide with EWSR1-FLI1 in active enhancers. While retaining its repressive canonical activity, we find RING1B as necessary for the expression of key EWSR1-FLI1 activated targets like NKX2-2, SOX2 or IGF1 where it mainly exerts a role in promoting oncogene recruitment to enhancers. Knockdown of RING1B is sufficient to impair growth of tumor xenografts and expression of EWSR1-FLI1 induced neomorphic enhancers in vivo. Restoration of RING1B ubiquitin ligase activity by the AURKB inhibitor AZD1152 decreases expression of RING1B/EWSR1-FLI1 common targets. Overall, our findings demonstrate RING1B as a critical modulator of EWSR1-FLI1 induced chromatin remodeling.
Project description:EWSR1-FLI1 genome reprogramming through remodeling of enhancers is determinant for Ewing sarcoma (ES) tumorigenesis. We describe a non-canonical function of RING1B, a PRC1 subunit highly expressed in primary ES tumors, co-localizing genome wide with EWSR1-FLI1 in active enhancers. While retaining its repressive canonical activity, we find RING1B as necessary for the expression of key EWSR1-FLI1 activated targets like NKX2-2, SOX2 or IGF1 where it mainly exerts a role in promoting oncogene recruitment to enhancers. Knockdown of RING1B is sufficient to impair growth of tumor xenografts and expression of EWSR1-FLI1 induced neomorphic enhancers in vivo. Restoration of RING1B ubiquitin ligase activity by the AURKB inhibitor AZD1152 decreases expression of RING1B/EWSR1-FLI1 common targets. Overall, our findings demonstrate RING1B as a critical modulator of EWSR1-FLI1 induced chromatin remodeling.
Project description:The Ewing Sarcoma cell lines A673, SK-ES-1, and SK-N-MC were treated with without 5-AZA to identify upregulated genes A673, SK-ES-1, and SK-N-MC were treated with 5-AZA
Project description:We report the application of single-molecule-based sequencing technology for high-throughput profiling of genes regulated under EWSR1-FLI1 expression in A673/TR/shEF. EWSR1-FLI1 specific small hairpin RNA was induced in A673/TR/shEF cells by adding DOX at 1 ug/mL. After 7 days, DOX was removed to allow silencing of the shRNA and induction of EWSR1-FLI1. Cells were harvested at seven different times points: 0 day (d7), 2 days (d9), 3 days (d10), 4 days (d11), 7 days (d14), 10 days (d17) and 15 days (d22) after DOX removal.
Project description:To get insight in the functional role of EGR2 for Ewing sarcoma, we performed a transcriptional profiling of Ewing sarcoma cells after knockdown of EGR2 and compared the resulting transcriptional signature with that of EWSR1-FLI1-silenced Ewing sarcoma cells. In accordance with the strong EGR2-induction by EWSR1-FLI1, both genes highly significantly overlap in their transcriptional signatures. Gene-set enrichment analyses (GSEA) and DAVID (Database for Annotation, Visualisation and Integrated Discovery) gene ontology analyses indicated a strong impact of EGR2 on cholesterol and lipid biosynthesis resembling its function in orchestrating lipid metabolism of myelinating Schwann cells. A673 and SK-N-MC Ewing sarcoma cells were transfected with specific siRNAs directed against EGR2 or EWSR1-FLI1 or non-targeting control siRNA. 48 h thereafter RNA was harvested and processed for microarray analysis.
Project description:Expression profiling of Ewing sarcoma samples in the frame of the CIT program from the french Ligue Nationale Contre le Cancer (http://cit.ligue-cancer.net). STAG2 loss-of-function mutation is the most frequent secondary genetic alteration in Ewing sarcoma, an aggressive bone tumor driven by the chimeric EWSR1-FLI1 transcription factor. STAG2 encodes an integral member of the cohesin complex, a ring-shaped multi-protein structure, which is essential to shape the architecture and expression of the genome with CTCF. Combining this cohort with our previously published series (GSE34620), we show that a signature of commonly downregulated genes upon STAG2 mutation in A673 and TC71 and linked to at least one EWSR1-FLI1 bound GGAA microsatellite enhancer chain element inferred form H3K27ac HiChIP predict poor overall survival in Ewing sarcoma patients.
Project description:STAG2, a member of cohesin, is one of the most recurrently mutated genes in human cancer. Here, we investigated STAG2 function in the context of Ewing sarcoma, an aggressive bone tumor driven by EWS-FLI1 oncogene chimeric transcription factor. Five different Ewing sarcoma cell lines were transfected with siCT or 2 different siRNAs targeting STAG2 (siSA2#6 or siSA2#8). RNA in A673 & TC71 (siSTAG2) was extracted 24, 48 and 72 hours post-transfection. RNA in EW1, CHLA-10 and CHLA-258 (siSTAG2 and siEWSR1-FLI1) was extracted 72 hours post-transfection. RNA-seq based anlayses of these experiments highligted that STAG2 knock-down alters EWSR1-FLI1 activation signature.
Project description:Polycomb repressive complex 1 (PRC1) catalyzes H2A monoubiquitination (uH2A) and regulates pluripotency in embryonic stem cells (ESCs). However the mechanisms controlling PRC1 recruitment and activity are largely unknown. Here we show that Fbxl10 interacts with Ring1B and Nspc1, forming a non-canonical PRC1. We demonstrate that Fbxl10-PRC1 is essential for H2A ubiquitination in mouse ESCs. Genome-wide analyses reveal that Fbxl10 preferentially binds to CpG islands and co-localizes with Ring1B on Polycomb target genes. Notably, Fbxl10 depletion causes modest dissociation of Ring1B but a major loss of uH2A on target genes. Furthermore rescue experiments for Fbxl10 reveal that its DNA binding capability and integration into PRC1 are required for proper H2A ubiquitination. ES cells lacking Fbxl10, like previously characterized Polycomb mutants, show a severely compromised capacity for successful differentiation. Our results shed light on a novel mechanism how CpG islands regulate chromatin function by affecting polycomb recruitment and activity. All ChIP-seq reactions were performed in either untransfected cells, cells expressing scrambled shRNA or Fbxl10 shRNA, Ring1b-/- or Suz12-/- mouse ES cells