Project description:RBPJ is the central transcription factor involved in the Notch-dependent transcriptional response. Ist repressive function is strongly dependent on its interaction with the corepressor SHARP. Here we analyzed the gomic binding of RBPJ wt, and different RBPJ mutants making use of RBPJ or SHARP depleted HeLa cells. and
Project description:piRNA-deficient Maelstrom (Mael) null mice are characterized by a strong upregulation of LINE-1 (L1) retrotransposon in meiotic spermatocytes. This defect turns out in the accumulation of L1 RNA and ORF1p in their cytoplasm and the formation of prominent ribonucleoprotein aggregates. We used 3-months-old Mael-/- male mice to characterize the RNA present in those ORF1p aggregates. To favor the isolation of complexed versus free ORF1p protein, we first fractionated Mael-/- testis extracts (that we refer to as TOTAL) by sucrose gradient ultracentrifugation, in the presence of EDTA. We then pooled the sucrose fractions where ORF1p macromolecular complexes sediment (fractions 5-8) and used this pool as the INPUT for an anti-ORF1p co-immunoprecipitation (IP) followed by RNA-seq.
Project description:Notch signaling activity governs widespread cellular differentiation in higher animals, including humans, and is involved in several congenital diseases and different forms of cancer. Notch signals are mediated by the transcriptional regulator RBPJ in a complex with activated Notch (NICD). Analysis of Notch pathway regulation in humans is hampered by a partial redundancy of the four Notch receptor copies, yet RBPJ is solitary, allowing its study in model systems. In Drosophila melanogaster, the RBPJ orthologue is encoded by Suppressor of Hairless [Su(H)]. Using genome engineering, we replaced Su(H) by murine RBPJ in order to study its function in the fly. In fact, RBPJ largely substitutes for Su(H)'s function, yet subtle phenotypes reflect increased Notch signaling activity. Accordingly, the binding of RBPJ to Hairless (H) protein, the general Notch antagonist in Drosophila, was considerably reduced compared to that of Su(H). An H-binding defective RBPJLLL mutant matched the respective Su(H)LLL allele: homozygotes were lethal due to extensive Notch hyperactivity. Moreover, RBPJLLL protein accumulated at lower levels than wild type RBPJ, except in the presence of NICD. Apparently, RBPJ protein stability depends on protein complex formation with either H or NICD, similar to Su(H), demonstrating that the murine homologue underlies the same regulatory mechanisms as Su(H) in Drosophila. These results underscore the importance of regulating the availability of RBPJ protein to correctly mediate Notch signaling activity in the fly.
Project description:Background & Aims: Combined HCC-iCCA is a rare liver tumor type and is often not well separated from HCC and iCCA. In this study, we analyzed major differences between combined HCC-iCCA and iCCA. Methods: We first characterized major differences between combined HCC-iCCA and iCCA by GSEA analysis. Consequently, we used CCl4 to induce chronic liver disease and subsequent liver carcinoma formation in mice. We forced the formation of combined HCC-iCCA through liver specific deletion of Rbpj, a key component of the Notch signaling pathway, in a Trp53 deficient background. Notch and p53 signaling pathways are involved in cellular differentiation processes and belong to the most affected pathways in liver carcinogenesis. Results: We show that combined HCC-iCCA can be separated from iCCA through differences in development related pathways, metabolism, cell to cell interaction and immune related pathways in human patients and in mice. Dysregulation of Notch signaling through a hepatocyte-specific Rbpj knockout resulted in an increased tumor burden and a high frequency of combined HCC-iCCA formation. In addition, hepatocytic loss of Rbpj forced M2 macrophage polarization and a tumor promoting environment. Conclusions: Dysregulation of Notch signaling is involved in tumor differentiation. Loss of Rbpj triggers the formation of combined HCC-iCCA which is associated by a pro-tumorigenic environment. Our study highlights the importance of dysfunctional Notch signalling through Rbpj deletion in hepatocytes. Rbpj loss affects tumor differentiation and the tumor microenvironment which can be linked to a combined HCC-iCCA phenotype seen in human patients.
Project description:NOTCH/RBPJ/MAML ternary transcriptional complex binds to regulatory element and drives gene expression. The complex can function as monomer and dimer. How dimeric complexes regulate gene expression in human cancer is not well studied. Here, we integrate genomic data sets and analyze Notch dimeric complexes-regulated transcriptome and cis-regulatory elements. A subset of coding and non-coding RNA is Notch dimeric complexes-associated. Dimeric complexes recognition sequence enriched in functional dynamic Notch sites and majority of dimer recognition sequence located in (super-)enhancers.
Project description:The transcriptional regulator Rbpj is involved in T-helper (TH) subset polarization, but its function in Treg cells remains unclear. Here we show that Treg-specific Rbpj deletion leads to splenomegaly and lymphadenopathy despite increased numbers of Treg cells with a polyclonal TCR repertoire. A specific defect of Rbpj-deficient Treg cells in controlling TH2 polarization and B cell responses was observed, leading to the spontaneous formation of germinal centers and a TH2-associated immunoglobulin class switch as well as T-cell polarization into TH2 effector cells. The observed phenotype was environment-dependent and could be induced by infection with parasitic nematodes. Rbpj-deficient Treg cells adopted open chromatin landscapes and gene expression profiles reminiscent of tissue-derived TH2-polarized Treg cells, with a prevailing footprint of transcription factor Gata-3. The over-expression of Ilt3 rendered Rbpj-deficient Treg cells incompatible to specifically restrain TH2 responses, finally leading to severe and fatal lymphoproliferative disease.
Project description:Dysregulation of the Notch-RBPJ signaling pathway has been found associated with various human diseases including cancers; however, precisely how this key signaling pathway is fine-tuned via its interactors and modifications is still largely unknown. In this study, using a proteomic approach, we identified FBXO42 as a novel RBPJ interactor. FBXO42 promotes RBPJ polyubiquitination on lysine (K) 175 via K63 linkage, which enhances the association of RBPJ with chromatin remodeling complexes and induces a global chromatin relaxation. Genetically depleting FBXO42 or pharmacologically targeting its E3 ligase activity attenuates the Notch signaling-related leukemia development in vivo. Taken together, our findings not only revealed FBXO42 as a critical regulator of the Notch pathway by modulating RBPJ-dependent global chromatin landscape changes, but also provide insights into the therapeutic intervention of the Notch pathway for leukemia treatment.
Project description:The main oncogenic driver in T-lymphoblastic leukemia (T-LL) is NOTCH1, which activates genes by forming chromatin-associated Notch transcription complexes. Gamma-secretase (GSI) inhibitor treatment prevents NOTCH1 nuclear localization, but most genes with NOTCH1 binding sites are insensitive to GSI. Here, we demonstrate that fewer than 10% of NOTCH1 binding sites show dynamic changes in NOTCH1 occupancy when T-LL cells are toggled between the Notch-on and –off states with GSI. Dynamic NOTCH1 sites are functional, being highly associated with Notch target genes, are located mainly in distal enhancers, and frequently overlap with RUNX1 binding. In line with the latter association, we show that expression of IL7R, a gene with key roles in normal T cell development and in T-LL, is coordinately regulated by Runx factors and dynamic NOTCH1 binding to distal enhancers. Like IL7R, most Notch target genes and associated dynamic NOTCH1 binding sites co-occupy chromatin domains defined by constitutive binding of CCCTC binding factor (CTCF), which appears to restrict the regulatory potential of dynamic NOTCH1 sites. More remarkably, the majority of dynamic NOTCH1 sites lie in super-enhancers, distal elements with exceptionally broad and high levels of H3K27ac. Changes in Notch occupancy produces dynamic alterations in H3K27ac levels across the entire breadth of super-enhancers and in the promoters of nearby Notch target genes. These findings link regulation of super-enhancer function to NOTCH1, a master regulatory factor and potent oncoprotein in the context of immature T cells, and delineate a generally applicable roadmap for identifying functional Notch sites in cellular genomes. NOTCH1/RBPJ complexes binding dynamics in human T-LL
Project description:Dysregulation of the Notch-RBPJ signaling pathway has been found associated with various human diseases including cancers; however, precisely how this key signaling pathway is fine-tuned via its interactors and modifications is still largely unknown. In this study, using a proteomic approach, we identified FBXO42 as a novel RBPJ interactor. FBXO42 promotes RBPJ polyubiquitination on lysine (K) 175 via K63 linkage, which enhances the association of RBPJ with chromatin remodeling complexes and induces a global chromatin relaxation. Genetically depleting FBXO42 or pharmacologically targeting its E3 ligase activity attenuates the Notch signaling-related leukemia development in vivo. Taken together, our findings not only revealed FBXO42 as a critical regulator of the Notch pathway by modulating RBPJ-dependent global chromatin landscape changes, but also provide insights into the therapeutic intervention of the Notch pathway for leukemia treatment.