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Fechner J, Ketelhut M, Maier D, Preiss A, Nagel AC. The Binding of CSL Proteins to Either Co-Activators or Co-Repressors Protects from Proteasomal Degradation Induced by MAPK-Dependent Phosphorylation. Int J Mol Sci 2022; 23:ijms232012336. [PMID: 36293193 PMCID: PMC9604145 DOI: 10.3390/ijms232012336] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Revised: 10/12/2022] [Accepted: 10/13/2022] [Indexed: 11/06/2022] Open
Abstract
The primary role of Notch is to specify cellular identities, whereby the cells respond to amazingly small changes in Notch signalling activity. Hence, dosage of Notch components is crucial to regulation. Central to Notch signal transduction are CSL proteins: together with respective cofactors, they mediate the activation or the silencing of Notch target genes. CSL proteins are extremely similar amongst species regarding sequence and structure. We noticed that the fly homologue suppressor of hairless (Su(H)) is stabilised in transcription complexes. Using specific transgenic fly lines and HeLa RBPJKO cells we provide evidence that Su(H) is subjected to proteasomal degradation with a half-life of about two hours if not protected by binding to co-repressor hairless or co-activator Notch. Moreover, Su(H) stability is controlled by MAPK-dependent phosphorylation, matching earlier data for RBPJ in human cells. The homologous murine and human RBPJ proteins, however, are largely resistant to degradation in our system. Mutating presumptive protein contact sites, however, sensitised RBPJ for proteolysis. Overall, our data highlight the similarities in the regulation of CSL protein stability across species and imply that turnover of CSL proteins may be a conserved means of regulating Notch signalling output directly at the level of transcription.
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Wolf DB, Maier D, Nagel AC. Nucleo-cytoplasmic shuttling of murine RBPJ by Hairless protein matches that of Su(H) protein in the model system Drosophila melanogaster. Hereditas 2021; 158:11. [PMID: 33775255 PMCID: PMC8006372 DOI: 10.1186/s41065-021-00175-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Accepted: 03/15/2021] [Indexed: 11/16/2022] Open
Abstract
Abstract CSL transcription factors are central to signal transduction in the highly conserved Notch signaling pathway. CSL acts as a molecular switch: depending on the cofactors recruited, CSL induces either activation or repression of Notch target genes. Unexpectedly, CSL depends on its cofactors for nuclear entry, despite its role as gene regulator. In Drosophila, the CSL homologue Suppressor of Hairless (Su(H)), recruits Hairless (H) for repressor complex assembly, and eventually for nuclear import. We recently found that Su(H) is subjected to a dynamic nucleo-cytoplasmic shuttling, thereby strictly following H subcellular distribution. Hence, regulation of nuclear availability of Su(H) by H may represent a new layer of control of Notch signaling activity. Here we extended this work on the murine CSL homologue RBPJ. Using a ‘murinized’ fly model bearing RBPJwt in place of Su(H) at the endogenous locus we demonstrate that RBPJ protein likewise follows H subcellular distribution. For example, overexpression of a H*NLS3 protein variant defective of nuclear import resulted in a cytosolic localization of RBPJ protein, whereas the overexpression of a H*NES protein variant defective in the nuclear export signal caused the accumulation of RBPJ protein in the nucleus. Evidently, RBPJ is exported from the nucleus as well. Overall these data demonstrate that in our fly model, RBPJ is subjected to H-mediated nucleo-cytoplasmic shuttling as is Su(H). These data raise the possibility that nuclear availability of mammalian CSL proteins is likewise restricted by cofactors, and may hence present a more general mode of regulating Notch signaling activity. Graphical abstract ![]()
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Affiliation(s)
- Dorina B Wolf
- Department of General Genetics (190g), University of Hohenheim, Garbenstr. 30, 70599, Stuttgart, Germany
| | - Dieter Maier
- Department of General Genetics (190g), University of Hohenheim, Garbenstr. 30, 70599, Stuttgart, Germany
| | - Anja C Nagel
- Department of General Genetics (190g), University of Hohenheim, Garbenstr. 30, 70599, Stuttgart, Germany.
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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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CSL-Associated Corepressor and Coactivator Complexes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1066:279-295. [PMID: 30030832 DOI: 10.1007/978-3-319-89512-3_14] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The highly conserved Notch signal transduction pathway orchestrates fundamental cellular processes including, differentiation, proliferation, and apoptosis during embryonic development and in the adult organism. Dysregulated Notch signaling underlies the etiology of a variety of human diseases, such as certain types of cancers, developmental disorders and cardiovascular disease. Ligand binding induces proteolytic cleavage of the Notch receptor and nuclear translocation of the Notch intracellular domain (NICD), which forms a ternary complex with the transcription factor CSL and the coactivator MAML to upregulate transcription of Notch target genes. The DNA-binding protein CSL is the centrepiece of transcriptional regulation in the Notch pathway, acting as a molecular hub for interactions with either corepressors or coactivators to repress or activate, respectively, transcription. Here we review previous structure-function studies of CSL-associated coregulator complexes and discuss the molecular insights gleaned from this research. We discuss the functional consequences of both activating and repressing binding partners using the same interaction platforms on CSL. We also emphasize that although there has been a significant uptick in structural information over the past decade, it is still under debate how the molecular switch from repression to activation mediated by CSL occurs at Notch target genes and whether it will be possible to manipulate these transcription complexes therapeutically in the future.
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Tabaja N, Yuan Z, Oswald F, Kovall RA. Structure-function analysis of RBP-J-interacting and tubulin-associated (RITA) reveals regions critical for repression of Notch target genes. J Biol Chem 2017; 292:10549-10563. [PMID: 28487372 DOI: 10.1074/jbc.m117.791707] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Revised: 05/04/2017] [Indexed: 11/06/2022] Open
Abstract
The Notch pathway is a cell-to-cell signaling mechanism that is essential for tissue development and maintenance, and aberrant Notch signaling has been implicated in various cancers, congenital defects, and cardiovascular diseases. Notch signaling activates the expression of target genes, which are regulated by the transcription factor CSL (CBF1/RBP-J, Su(H), Lag-1). CSL interacts with both transcriptional corepressor and coactivator proteins, functioning as both a repressor and activator, respectively. Although Notch activation complexes are relatively well understood at the structural level, less is known about how CSL interacts with corepressors. Recently, a new RBP-J (mammalian CSL ortholog)-interacting protein termed RITA has been identified and shown to export RBP-J out of the nucleus, thereby leading to the down-regulation of Notch target gene expression. However, the molecular details of RBP-J/RITA interactions are unclear. Here, using a combination of biochemical/cellular, structural, and biophysical techniques, we demonstrate that endogenous RBP-J and RITA proteins interact in cells, map the binding regions necessary for RBP-J·RITA complex formation, and determine the X-ray structure of the RBP-J·RITA complex bound to DNA. To validate the structure and glean more insights into function, we tested structure-based RBP-J and RITA mutants with biochemical/cellular assays and isothermal titration calorimetry. Whereas our structural and biophysical studies demonstrate that RITA binds RBP-J similarly to the RAM (RBP-J-associated molecule) domain of Notch, our biochemical and cellular assays suggest that RITA interacts with additional regions in RBP-J. Taken together, these results provide molecular insights into the mechanism of RITA-mediated regulation of Notch signaling, contributing to our understanding of how CSL functions as a transcriptional repressor of Notch target genes.
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Affiliation(s)
- Nassif Tabaja
- From the Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267 and
| | - Zhenyu Yuan
- From the Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267 and
| | - Franz Oswald
- the Department of Internal Medicine I, Center for Internal Medicine, University Medical Center Ulm, 89081 Ulm, Germany
| | - Rhett A Kovall
- From the Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267 and
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Contreras-Cornejo H, Saucedo-Correa G, Oviedo-Boyso J, Valdez-Alarcón JJ, Baizabal-Aguirre VM, Cajero-Juárez M, Bravo-Patiño A. The CSL proteins, versatile transcription factors and context dependent corepressors of the notch signaling pathway. Cell Div 2016; 11:12. [PMID: 27708688 PMCID: PMC5037638 DOI: 10.1186/s13008-016-0025-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Accepted: 09/16/2016] [Indexed: 12/24/2022] Open
Abstract
The Notch signaling pathway is a reiteratively used cell to cell communication pathway that triggers pleiotropic effects. The correct regulation of the pathway permits the efficient regulation of genes involved in cell fate decision throughout development. This activity relies notably on the CSL proteins, (an acronym for CBF-1/RBPJ-κ in Homo sapiens/Mus musculus respectively, Suppressor of Hairless in Drosophila melanogaster, Lag-1 in Caenorhabditis elegans) which is the unique transcription factor and DNA binding protein involved in this pathway. The CSL proteins have the capacity to recruit activation or repression complexes according to the cellular context. The aim of this review is to describe the different co-repressor proteins that interact directly with CSL proteins to form repression complexes thereby regulating the Notch signaling pathway in animal cells to give insights into the paralogous evolution of these co-repressors in higher eumetazoans and their subsequent effects at developmental processes.
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Affiliation(s)
- Humberto Contreras-Cornejo
- Centro Multidisciplinario de Estudios en Biotecnología (CMEB) de la Facultad de Medicina Veterinaria y Zootecnia, Universidad Michoacana de San Nicolás de Hidalgo, Posta Veterinaria, Km. 9.5 Carretera Morelia-Zinapécuaro, Col. La Palma, C. P. 58890 Tarímbaro, Mich. México
| | - Germán Saucedo-Correa
- Centro Multidisciplinario de Estudios en Biotecnología (CMEB) de la Facultad de Medicina Veterinaria y Zootecnia, Universidad Michoacana de San Nicolás de Hidalgo, Posta Veterinaria, Km. 9.5 Carretera Morelia-Zinapécuaro, Col. La Palma, C. P. 58890 Tarímbaro, Mich. México
| | - Javier Oviedo-Boyso
- Centro Multidisciplinario de Estudios en Biotecnología (CMEB) de la Facultad de Medicina Veterinaria y Zootecnia, Universidad Michoacana de San Nicolás de Hidalgo, Posta Veterinaria, Km. 9.5 Carretera Morelia-Zinapécuaro, Col. La Palma, C. P. 58890 Tarímbaro, Mich. México
| | - Juan José Valdez-Alarcón
- Centro Multidisciplinario de Estudios en Biotecnología (CMEB) de la Facultad de Medicina Veterinaria y Zootecnia, Universidad Michoacana de San Nicolás de Hidalgo, Posta Veterinaria, Km. 9.5 Carretera Morelia-Zinapécuaro, Col. La Palma, C. P. 58890 Tarímbaro, Mich. México
| | - Víctor Manuel Baizabal-Aguirre
- Centro Multidisciplinario de Estudios en Biotecnología (CMEB) de la Facultad de Medicina Veterinaria y Zootecnia, Universidad Michoacana de San Nicolás de Hidalgo, Posta Veterinaria, Km. 9.5 Carretera Morelia-Zinapécuaro, Col. La Palma, C. P. 58890 Tarímbaro, Mich. México
| | - Marcos Cajero-Juárez
- Instituto de Investigaciones Agropecuarias y Forestales (IIAF), Universidad Michoacana de San Nicolás de Hidalgo, Km. 9.5 Carretera Morelia-Zinapécuaro, Col. La Palma, C. P. 58890 Tarímbaro, Mich. México
| | - Alejandro Bravo-Patiño
- Centro Multidisciplinario de Estudios en Biotecnología (CMEB) de la Facultad de Medicina Veterinaria y Zootecnia, Universidad Michoacana de San Nicolás de Hidalgo, Posta Veterinaria, Km. 9.5 Carretera Morelia-Zinapécuaro, Col. La Palma, C. P. 58890 Tarímbaro, Mich. México
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