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Maier D, Bauer M, Boger M, Sanchez Jimenez A, Yuan Z, Fechner J, Scharpf J, Kovall RA, Preiss A, Nagel AC. Genetic and Molecular Interactions between HΔCT, a Novel Allele of the Notch Antagonist Hairless, and the Histone Chaperone Asf1 in Drosophila melanogaster. Genes (Basel) 2023; 14:205. [PMID: 36672946 PMCID: PMC9858708 DOI: 10.3390/genes14010205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 01/03/2023] [Accepted: 01/09/2023] [Indexed: 01/15/2023] Open
Abstract
Cellular differentiation relies on the highly conserved Notch signaling pathway. Notch activity induces gene expression changes that are highly sensitive to chromatin landscape. We address Notch gene regulation using Drosophila as a model, focusing on the genetic and molecular interactions between the Notch antagonist Hairless and the histone chaperone Asf1. Earlier work implied that Asf1 promotes the silencing of Notch target genes via Hairless (H). Here, we generate a novel HΔCT allele by genome engineering. Phenotypically, HΔCT behaves as a Hairless gain of function allele in several developmental contexts, indicating that the conserved CT domain of H has an attenuator role under native biological contexts. Using several independent methods to assay protein-protein interactions, we define the sequences of the CT domain that are involved in Hairless-Asf1 binding. Based on previous models, where Asf1 promotes Notch repression via Hairless, a loss of Asf1 binding should reduce Hairless repressive activity. However, tissue-specific Asf1 overexpression phenotypes are increased, not rescued, in the HΔCT background. Counterintuitively, Hairless protein binding mitigates the repressive activity of Asf1 in the context of eye development. These findings highlight the complex connections of Notch repressors and chromatin modulators during Notch target-gene regulation and open the avenue for further investigations.
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Affiliation(s)
- Dieter Maier
- Institute of Biology, Genetics Department 190g, University of Hohenheim, Garbenstr. 30, D-70599 Stuttgart, Germany
| | - Milena Bauer
- Institute of Biology, Genetics Department 190g, University of Hohenheim, Garbenstr. 30, D-70599 Stuttgart, Germany
- Biozentrum, University of Basel, Spitalstrasse 41, CH-4056 Basel, Switzerland
| | - Mike Boger
- Institute of Biology, Genetics Department 190g, University of Hohenheim, Garbenstr. 30, D-70599 Stuttgart, Germany
- European Center for Angioscience, Medical Faculty Mannheim, Heidelberg University, Ludolf-Krehl-Straße 13–17, D-68167 Mannheim, Germany
| | - Anna Sanchez Jimenez
- Institute of Biology, Genetics Department 190g, University of Hohenheim, Garbenstr. 30, D-70599 Stuttgart, Germany
| | - Zhenyu Yuan
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Medical Sciences Building 2201, Albert Sabin Way, Cincinnati, OH 45267, USA
| | - Johannes Fechner
- Institute of Biology, Genetics Department 190g, University of Hohenheim, Garbenstr. 30, D-70599 Stuttgart, Germany
- Institute of Biomedical Genetics (IBMG), University of Stuttgart, Allmandring 31, D-70569 Stuttgart, Germany
| | - Janika Scharpf
- Institute of Biology, Genetics Department 190g, University of Hohenheim, Garbenstr. 30, D-70599 Stuttgart, Germany
| | - Rhett A. Kovall
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Medical Sciences Building 2201, Albert Sabin Way, Cincinnati, OH 45267, USA
| | - Anette Preiss
- Institute of Biology, Genetics Department 190g, University of Hohenheim, Garbenstr. 30, D-70599 Stuttgart, Germany
| | - Anja C. Nagel
- Institute of Biology, Genetics Department 190g, University of Hohenheim, Garbenstr. 30, D-70599 Stuttgart, Germany
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Maier D. Membrane-Anchored Hairless Protein Restrains Notch Signaling Activity. Genes (Basel) 2020; 11:genes11111315. [PMID: 33171957 PMCID: PMC7694644 DOI: 10.3390/genes11111315] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 11/03/2020] [Accepted: 11/04/2020] [Indexed: 11/16/2022] Open
Abstract
The Notch signaling pathway governs cell-to-cell communication in higher eukaryotes. In Drosophila, after cleavage of the transmembrane receptor Notch, the intracellular domain of Notch (ICN) binds to the transducer Suppressor of Hairless (Su(H)) and shuttles into the nucleus to activate Notch target genes. Similarly, the Notch antagonist Hairless transfers Su(H) into the nucleus to repress Notch target genes. With the aim to prevent Su(H) nuclear translocation, Hairless was fused to a transmembrane domain to anchor the protein at membranes. Indeed, endogenous Su(H) co-localized with membrane-anchored Hairless, demonstrating their binding in the cytoplasm. Moreover, adult phenotypes uncovered a loss of Notch activity, in support of membrane-anchored Hairless sequestering Su(H) in the cytosol. A combined overexpression of membrane-anchored Hairless with Su(H) lead to tissue proliferation, which is in contrast to the observed apoptosis after ectopic co-overexpression of the wild-type genes, indicating a shift to a gain of Notch activity. A mixed response, general de-repression of Notch signaling output, plus inhibition at places of highest Notch activity, perhaps reflects Su(H)’s role as activator and repressor, supported by results obtained with the Hairless-binding deficient Su(H)LLL mutant, inducing activation only. Overall, the results strengthen the idea of Su(H) and Hairless complex formation within the cytosolic compartment.
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Affiliation(s)
- Dieter Maier
- Deptartment of General Genetics 190g, University of Hohenheim, Garbenstr. 30, 70599 Stuttgart, Germany
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Yuan Z, VanderWielen BD, Giaimo BD, Pan L, Collins CE, Turkiewicz A, Hein K, Oswald F, Borggrefe T, Kovall RA. Structural and Functional Studies of the RBPJ-SHARP Complex Reveal a Conserved Corepressor Binding Site. Cell Rep 2020; 26:845-854.e6. [PMID: 30673607 PMCID: PMC6352735 DOI: 10.1016/j.celrep.2018.12.097] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 11/05/2018] [Accepted: 12/21/2018] [Indexed: 11/28/2022] Open
Abstract
Notch is a conserved signaling pathway that is essential for metazoan development and homeostasis; dysregulated signaling underlies the pathophysiology of numerous human diseases. Receptor-ligand interactions result in gene expression changes, which are regulated by the transcription factor RBPJ. RBPJ forms a complex with the intracellular domain of the Notch receptor and the coactivator Mastermind to activate transcription, but it can also function as a repressor by interacting with corepressor proteins. Here, we determine the structure of RBPJ bound to the corepressor SHARP and DNA, revealing its mode of binding to RBPJ. We tested structure-based mutants in biophysical and biochemical-cellular as-says to characterize the role of RBPJ as a repressor, clearly demonstrating that RBPJ mutants deficient for SHARP binding are incapable of repressing transcription of genes responsive to Notch signaling in cells. Altogether, our structure-function studies provide significant insights into the repressor function of RBPJ. Yuan et al. determine the X-ray structure of the corepressor SHARP bound to RBPJ, the nuclear effector of the Notch pathway. The structure-function analysis provides insights into corepressor binding to RBPJ and how RBPJ functions as a repressor of transcription of Notch target genes.
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Affiliation(s)
- Zhenyu Yuan
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Bradley D VanderWielen
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | | | - Leiling Pan
- Department of Internal Medicine I, Center for Internal Medicine, University Medical Center Ulm, 89081 Ulm, Germany
| | - Courtney E Collins
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | | | - Kerstin Hein
- Institute of Biochemistry, University of Giessen, Giessen, Germany
| | - Franz Oswald
- Department of Internal Medicine I, Center for Internal Medicine, University Medical Center Ulm, 89081 Ulm, Germany
| | - Tilman Borggrefe
- Institute of Biochemistry, University of Giessen, Giessen, Germany
| | - Rhett A Kovall
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
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Wolf D, Smylla TK, Reichmuth J, Hoffmeister P, Kober L, Zimmermann M, Turkiewicz A, Borggrefe T, Nagel AC, Oswald F, Preiss A, Maier D. Nucleo-cytoplasmic shuttling of Drosophila Hairless/Su(H) heterodimer as a means of regulating Notch dependent transcription. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1866:1520-1532. [PMID: 31326540 DOI: 10.1016/j.bbamcr.2019.07.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Revised: 07/02/2019] [Accepted: 07/16/2019] [Indexed: 12/21/2022]
Abstract
Activation and repression of Notch target genes is mediated by transcription factor CSL, known as Suppressor of Hairless (Su(H)) in Drosophila and CBF1 or RBPJ in human. CSL associates either with co-activator Notch or with co-repressors such as Drosophila Hairless. The nuclear translocation of transcription factor CSL relies on co-factor association, both in mammals and in Drosophila. The Drosophila CSL orthologue Su(H) requires Hairless for repressor complex formation. Based on its role in transcriptional silencing, H protein would be expected to be strictly nuclear. However, H protein is also cytosolic, which may relate to its role in the stabilization and nuclear translocation of Su(H) protein. Here, we investigate the function of the predicted nuclear localization signals (NLS 1-3) and single nuclear export signal (NES) of co-repressor Hairless using GFP-fusion proteins, reporter assays and in vivo analyses using Hairless wild type and shuttling-defective Hairless mutants. We identify NLS3 and NES to be critical for Hairless function. In fact, H⁎NLS3 mutant flies match H null mutants, whereas H⁎NLS3⁎NES double mutants display weaker phenotypes in agreement with a crucial role for NES in H export. As expected for a transcriptional repressor, Notch target genes are deregulated in H⁎NLS3 mutant cells, demonstrating nuclear requirement for its activity. Importantly, we reveal that Su(H) protein strictly follows Hairless protein localization. Together, we propose that shuttling between the nucleo-cytoplasmic compartments provides the possibility to fine tune the regulation of Notch target gene expression by balancing of Su(H) protein availability for Notch activation.
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Affiliation(s)
- Dorina Wolf
- University of Hohenheim, Institute of Genetics (240a), Garbenstr. 30, 70599 Stuttgart, Germany
| | - Thomas K Smylla
- University of Hohenheim, Institute of Genetics (240a), Garbenstr. 30, 70599 Stuttgart, Germany
| | - Jan Reichmuth
- University of Hohenheim, Institute of Genetics (240a), Garbenstr. 30, 70599 Stuttgart, Germany
| | - Philipp Hoffmeister
- University Medical Center Ulm, Center for Internal Medicine, Department of Internal Medicine I, Albert-Einstein-Allee 23, 89081 Ulm, Germany
| | - Ludmilla Kober
- University of Hohenheim, Institute of Genetics (240a), Garbenstr. 30, 70599 Stuttgart, Germany
| | - Mirjam Zimmermann
- University of Hohenheim, Institute of Genetics (240a), Garbenstr. 30, 70599 Stuttgart, Germany
| | - Aleksandra Turkiewicz
- Justus-Liebig University of Giessen Institute of Biochemistry, Friedrichstrasse 24, 35392 Giessen, Germany
| | - Tilman Borggrefe
- Justus-Liebig University of Giessen Institute of Biochemistry, Friedrichstrasse 24, 35392 Giessen, Germany
| | - Anja C Nagel
- University of Hohenheim, Institute of Genetics (240a), Garbenstr. 30, 70599 Stuttgart, Germany
| | - Franz Oswald
- University Medical Center Ulm, Center for Internal Medicine, Department of Internal Medicine I, Albert-Einstein-Allee 23, 89081 Ulm, Germany
| | - Anette Preiss
- University of Hohenheim, Institute of Genetics (240a), Garbenstr. 30, 70599 Stuttgart, Germany
| | - Dieter Maier
- University of Hohenheim, Institute of Genetics (240a), Garbenstr. 30, 70599 Stuttgart, Germany.
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Maier D. The evolution of transcriptional repressors in the Notch signaling pathway: a computational analysis. Hereditas 2019; 156:5. [PMID: 30679936 PMCID: PMC6337844 DOI: 10.1186/s41065-019-0081-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Accepted: 01/09/2019] [Indexed: 11/18/2022] Open
Abstract
Background The Notch signaling pathway governs the specification of different cell types in flies, nematodes and vertebrates alike. Principal components of the pathway that activate Notch target genes are highly conserved throughout the animal kingdom. Despite the impact on development and disease, repression mechanisms are less well studied. Repressors are known from arthropods and vertebrates that differ strikingly by mode of action: whereas Drosophila Hairless assembles repressor complexes with CSL transcription factors, competition between activator and repressors occurs in vertebrates (for example SHARP/MINT and KyoT2). This divergence raises questions on the evolution: Are there common ancestors throughout the animal kingdom? Results Available genome databases representing all animal clades were searched for homologues of Hairless, SHARP and KyoT2. The most distant species with convincing Hairless orthologs belong to Myriapoda, indicating its emergence after the Mandibulata-Chelicarata radiation about 500 million years ago. SHARP shares motifs with SPEN and SPENITO proteins, present throughout the animal kingdom. The CSL interacting domain of SHARP, however, is specific to vertebrates separated by roughly 600 million years of evolution. KyoT2 bears a C-terminal CSL interaction domain (CID), present only in placental mammals but highly diverged already in marsupials, suggesting introduction roughly 100 million years ago. Based on the LIM-domains that characterize KyoT2, homologues can be found in Drosophila melanogaster (Limpet) and Hydra vulgaris (Prickle 3 like). These lack the CID of KyoT2, however, contain a PET and additional LIM domains. Conservation of intron/exon boundaries underscores the phylogenetic relationship between KyoT2, Limpet and Prickle. Most strikingly, Limpet and Prickle proteins carry a tetra-peptide motif resembling that of several CSL interactors. Overall, KyoT2 may have evolved from prickle and Limpet to a Notch repressor in mammals. Conclusions Notch repressors appear to be specific to either chordates or arthropods. Orthologues of experimentally validated repressors were not found outside the phylogenetic group they have been originally identified. However, the data provide a hypothesis on the evolution of mammalian KyoT2 from Prickle like ancestors. The finding of a potential CSL interacting domain in Prickle homologues points to a novel, very ancestral CSL interactor present in the entire animal kingdom. Electronic supplementary material The online version of this article (10.1186/s41065-019-0081-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Dieter Maier
- Institute of Genetics (240), University of Hohenheim, Garbenstr. 30, 70599 Stuttgart, Germany
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The Notch repressor complex in Drosophila: in vivo analysis of Hairless mutants using overexpression experiments. Dev Genes Evol 2019; 229:13-24. [PMID: 30612166 DOI: 10.1007/s00427-018-00624-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Accepted: 12/17/2018] [Indexed: 10/27/2022]
Abstract
During development of higher animals, the Notch signalling pathway governs cell type specification by mediating appropriate gene expression responses. In the absence of signalling, Notch target genes are silenced by repressor complexes. In the model organism Drosophila melanogaster, the repressor complex includes the transcription factor Suppressor of Hairless [Su(H)] and Hairless (H) plus general co-repressors. Recent crystal structure analysis of the Drosophila Notch repressor revealed details of the Su(H)-H complex. They were confirmed by mutational analyses of either protein; however, only Su(H) mutants have been further studied in vivo. Here, we analyse three H variants predicted to affect Su(H) binding. To this end, amino acid replacements Phenylalanine 237, Leucines 245 and 247, as well as Tryptophan 258 to Alanine were introduced into the H protein. A cell-based reporter assay indicates substantial loss of Su(H) binding to the respective mutant proteins HFA, HLLAA and HWA. For in vivo analysis, UAS-lines HFA, HLLAA and HWA were generated to allow spatially restricted overexpression. In these assays, all three mutants resembled the HLD control, shown before to lack Su(H) binding, indicating a strong reduction of H activity. For example, the H variants were impaired in wing margin formation, but unexpectedly induced ectopic wing venation. Concurrent overexpression with Su(H), however, suggests that all mutant H protein isoforms are still able to bind Su(H) in vivo. We conclude that a weakening of the cohesion in the H-Su(H) repressor complex is sufficient for disrupting its in vivo functionality.
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