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Reddy Onteddu V, Bhattacharya A, Baker NE. The Id protein Extramacrochaetae restrains the E protein Daughterless to regulate Notch, Rap1, and Sevenless within the R7 equivalence group of the Drosophila eye. Biol Open 2024; 13:bio060124. [PMID: 39041866 PMCID: PMC11360143 DOI: 10.1242/bio.060124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Accepted: 07/15/2024] [Indexed: 07/24/2024] Open
Abstract
The Drosophila Id gene extramacrochaetae (emc) is required during Drosophila eye development for proper cell fate specification within the R7 equivalence group. Without emc, R7 cells develop like R1/6 cells, and there are delays and deficits in differentiation of non-neuronal cone cells. Although emc encodes an Inhibitor of DNA-binding (Id) protein that is known to antagonize proneural bHLH protein function, no proneural gene is known for R7 or cone cell fates. These fates are also independent of daughterless (da), which encodes the ubiquitous E protein heterodimer partner of proneural bHLH proteins. We report here that the effects of emc mutations disappear in the absence of da, and are partially mimicked by forced expression of Da dimers, indicating that emc normally restrains da from interfering with R7 and cone cell specification, as occurs in emc mutants. emc, and da, regulate three known contributors to R7 fate, which are Notch signaling, Rap1, and Sevenless. R7 specification is partially restored to emc mutant cells by mutation of RapGap1, confirming that Rap1 activity, in addition to Notch activity, is a critical target of emc. These findings exemplify how mutations of an Id protein gene can affect processes that do not require any bHLH protein, by restraining Da activity within physiological bounds.
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Affiliation(s)
- Venkateswara Reddy Onteddu
- Department of Genetics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461,USA
| | - Abhishek Bhattacharya
- Department of Genetics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461,USA
| | - Nicholas E. Baker
- Department of Genetics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461,USA
- Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461,USA
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461,USA
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Wąchalska M, Riepe C, Ślusarz MJ, Graul M, Borowski LS, Qiao W, Foltyńska M, Carette JE, Bieńkowska-Szewczyk K, Szczesny RJ, Kopito RR, Lipińska AD. The herpesvirus UL49.5 protein hijacks a cellular C-degron pathway to drive TAP transporter degradation. Proc Natl Acad Sci U S A 2024; 121:e2309841121. [PMID: 38442151 PMCID: PMC10945846 DOI: 10.1073/pnas.2309841121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Accepted: 12/29/2023] [Indexed: 03/07/2024] Open
Abstract
The transporter associated with antigen processing (TAP) is a key player in the major histocompatibility class I-restricted antigen presentation and an attractive target for immune evasion by viruses. Bovine herpesvirus 1 impairs TAP-dependent antigenic peptide transport through a two-pronged mechanism in which binding of the UL49.5 gene product to TAP both inhibits peptide transport and triggers its proteasomal degradation. How UL49.5 promotes TAP degradation has, so far, remained unknown. Here, we use high-content siRNA and genome-wide CRISPR-Cas9 screening to identify CLR2KLHDC3 as the E3 ligase responsible for UL49.5-triggered TAP disposal. We propose that the C terminus of UL49.5 mimics a C-end rule degron that recruits the E3 to TAP and engages the cullin-RING E3 ligase in endoplasmic reticulum-associated degradation.
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Affiliation(s)
- Magda Wąchalska
- Laboratory of Virus Molecular Biology, Intercollegiate Faculty of Biotechnology, University of Gdańsk and Medical University of Gdańsk, Gdańsk80-307, Poland
- Department of Biology, Stanford University, Stanford, CA94305
| | - Celeste Riepe
- Department of Biology, Stanford University, Stanford, CA94305
| | - Magdalena J. Ślusarz
- Department of Theoretical Chemistry, Faculty of Chemistry, University of Gdańsk, Gdańsk80-308, Poland
| | - Małgorzata Graul
- Laboratory of Virus Molecular Biology, Intercollegiate Faculty of Biotechnology, University of Gdańsk and Medical University of Gdańsk, Gdańsk80-307, Poland
| | - Lukasz S. Borowski
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw02-106, Poland
| | - Wenjie Qiao
- Department of Microbiology and Immunology, Stanford University, Stanford, CA94305
| | - Michalina Foltyńska
- Laboratory of Virus Molecular Biology, Intercollegiate Faculty of Biotechnology, University of Gdańsk and Medical University of Gdańsk, Gdańsk80-307, Poland
| | - Jan E. Carette
- Department of Microbiology and Immunology, Stanford University, Stanford, CA94305
| | - Krystyna Bieńkowska-Szewczyk
- Laboratory of Virus Molecular Biology, Intercollegiate Faculty of Biotechnology, University of Gdańsk and Medical University of Gdańsk, Gdańsk80-307, Poland
| | - Roman J. Szczesny
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw02-106, Poland
| | - Ron R. Kopito
- Department of Biology, Stanford University, Stanford, CA94305
| | - Andrea D. Lipińska
- Laboratory of Virus Molecular Biology, Intercollegiate Faculty of Biotechnology, University of Gdańsk and Medical University of Gdańsk, Gdańsk80-307, Poland
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3
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Wąhalska M, Riepe C, Ślusarz MJ, Graul M, Borowski LS, Qiao W, Foltynska M, Carette JE, Bieńkowska-Szewczyk K, Szczesny RJ, Kopito RR, Lipińska AD. The herpesvirus UL49.5 protein hijacks a cellular C-degron pathway to drive TAP transporter degradation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.27.559663. [PMID: 37808699 PMCID: PMC10557673 DOI: 10.1101/2023.09.27.559663] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/10/2023]
Abstract
The transporter associated with antigen processing (TAP) is a key player in the MHC class I-restricted antigen presentation and an attractive target for immune evasion by viruses. Bovine herpesvirus 1 (BoHV-1) impairs TAP-dependent antigenic peptide transport through a two-pronged mechanism in which binding of the UL49.5 gene product to TAP both inhibits peptide transport and promotes its proteasomal degradation. How UL49.5 promotes TAP degradation is unknown. Here, we use high-content siRNA and genome-wide CRISPR-Cas9 screening to identify CLR2KLHDC3 as the E3 ligase responsible for UL49.5-triggered TAP disposal in human cells. We propose that the C-terminus of UL49.5 mimics a C-end rule degron that recruits the E3 to TAP and engages the CRL2 E3 in ER-associated degradation.
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Affiliation(s)
- Magda Wąhalska
- Laboratory of Virus Molecular Biology, Intercollegiate Faculty of Biotechnology, University of Gdańsk and Medical University of Gdańsk, 80-307 Gdańsk, Poland
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Celeste Riepe
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Magdalena J. Ślusarz
- Department of Theoretical Chemistry, Faculty of Chemistry, University of Gdańsk, 80-308 Gdańsk, Poland
| | - Małgorzata Graul
- Laboratory of Virus Molecular Biology, Intercollegiate Faculty of Biotechnology, University of Gdańsk and Medical University of Gdańsk, 80-307 Gdańsk, Poland
| | - Lukasz S. Borowski
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, 02-106 Warsaw, Poland
| | - Wenjie Qiao
- Department of Microbiology and Immunology, Stanford University, Stanford, CA 94305, USA
| | - Michalina Foltynska
- Laboratory of Virus Molecular Biology, Intercollegiate Faculty of Biotechnology, University of Gdańsk and Medical University of Gdańsk, 80-307 Gdańsk, Poland
| | - Jan E. Carette
- Department of Microbiology and Immunology, Stanford University, Stanford, CA 94305, USA
| | - Krystyna Bieńkowska-Szewczyk
- Laboratory of Virus Molecular Biology, Intercollegiate Faculty of Biotechnology, University of Gdańsk and Medical University of Gdańsk, 80-307 Gdańsk, Poland
| | - Roman J. Szczesny
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Ron R. Kopito
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Andrea D. Lipińska
- Laboratory of Virus Molecular Biology, Intercollegiate Faculty of Biotechnology, University of Gdańsk and Medical University of Gdańsk, 80-307 Gdańsk, Poland
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ASC proneural factors are necessary for chromatin remodeling during neuroectodermal to neuroblast fate transition to ensure the timely initiation of the neural stem cell program. BMC Biol 2022; 20:107. [PMID: 35549704 PMCID: PMC9102361 DOI: 10.1186/s12915-022-01300-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Accepted: 04/20/2022] [Indexed: 11/11/2022] Open
Abstract
Background In both Drosophila and mammals, the achaete-scute (ASC/ASCL) proneural bHLH transcription factors are expressed in the developing central and peripheral nervous systems, where they function during specification and maintenance of the neural stem cells in opposition to Notch signaling. In addition to their role in nervous system development, ASC transcription factors are oncogenic and exhibit chromatin reprogramming activity; however, the impact of ASC on chromatin dynamics during neural stem cell generation remains elusive. Here, we investigate the chromatin changes accompanying neural commitment using an integrative genetics and genomics methodology. Results We found that ASC factors bind equally strongly to two distinct classes of cis-regulatory elements: open regions remodeled earlier during maternal to zygotic transition by Zelda and less accessible, Zelda-independent regions. Both classes of cis-elements exhibit enhanced chromatin accessibility during neural specification and correlate with transcriptional regulation of genes involved in a variety of biological processes necessary for neuroblast function/homeostasis. We identified an ASC-Notch regulated TF network that includes likely prime regulators of neuroblast function. Using a cohort of ASC target genes, we report that ASC null neuroblasts are defectively specified, remaining initially stalled, unable to divide, and lacking expression of many proneural targets. When mutant neuroblasts eventually start proliferating, they produce compromised progeny. Reporter lines driven by proneural-bound enhancers display ASC dependency, suggesting that the partial neuroblast identity seen in the absence of ASC genes is likely driven by other, proneural-independent, cis-elements. Neuroblast impairment and the late differentiation defects of ASC mutants are corrected by ectodermal induction of individual ASC genes but not by individual members of the TF network downstream of ASC. However, in wild-type embryos, the induction of individual members of this network induces CNS hyperplasia, suggesting that they synergize with the activating function of ASC to consolidate the chromatin dynamics that promote neural specification. Conclusions We demonstrate that ASC proneural transcription factors are indispensable for the timely initiation of the neural stem cell program at the chromatin level by regulating a large number of enhancers in the vicinity of neural genes. This early chromatin remodeling is crucial for both neuroblast homeostasis as well as future progeny fidelity. Supplementary Information The online version contains supplementary material available at 10.1186/s12915-022-01300-8.
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Oproescu AM, Han S, Schuurmans C. New Insights Into the Intricacies of Proneural Gene Regulation in the Embryonic and Adult Cerebral Cortex. Front Mol Neurosci 2021; 14:642016. [PMID: 33658912 PMCID: PMC7917194 DOI: 10.3389/fnmol.2021.642016] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Accepted: 01/26/2021] [Indexed: 12/21/2022] Open
Abstract
Historically, the mammalian brain was thought to lack stem cells as no new neurons were found to be made in adulthood. That dogma changed ∼25 years ago with the identification of neural stem cells (NSCs) in the adult rodent forebrain. However, unlike rapidly self-renewing mature tissues (e.g., blood, intestinal crypts, skin), the majority of adult NSCs are quiescent, and those that become 'activated' are restricted to a few neurogenic zones that repopulate specific brain regions. Conversely, embryonic NSCs are actively proliferating and neurogenic. Investigations into the molecular control of the quiescence-to-proliferation-to-differentiation continuum in the embryonic and adult brain have identified proneural genes encoding basic-helix-loop-helix (bHLH) transcription factors (TFs) as critical regulators. These bHLH TFs initiate genetic programs that remove NSCs from quiescence and drive daughter neural progenitor cells (NPCs) to differentiate into specific neural cell subtypes, thereby contributing to the enormous cellular diversity of the adult brain. However, new insights have revealed that proneural gene activities are context-dependent and tightly regulated. Here we review how proneural bHLH TFs are regulated, with a focus on the murine cerebral cortex, drawing parallels where appropriate to other organisms and neural tissues. We discuss upstream regulatory events, post-translational modifications (phosphorylation, ubiquitinylation), protein-protein interactions, epigenetic and metabolic mechanisms that govern bHLH TF expression, stability, localization, and consequent transactivation of downstream target genes. These tight regulatory controls help to explain paradoxical findings of changes to bHLH activity in different cellular contexts.
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Affiliation(s)
- Ana-Maria Oproescu
- Sunnybrook Research Institute, Biological Sciences Platform, Toronto, ON, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada
| | - Sisu Han
- Sunnybrook Research Institute, Biological Sciences Platform, Toronto, ON, Canada
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Carol Schuurmans
- Sunnybrook Research Institute, Biological Sciences Platform, Toronto, ON, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
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6
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Abraham-Juárez MJ, Schrager-Lavelle A, Man J, Whipple C, Handakumbura P, Babbitt C, Bartlett M. Evolutionary Variation in MADS Box Dimerization Affects Floral Development and Protein Abundance in Maize. THE PLANT CELL 2020; 32:3408-3424. [PMID: 32873631 PMCID: PMC7610293 DOI: 10.1105/tpc.20.00300] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 08/19/2020] [Accepted: 09/01/2020] [Indexed: 05/19/2023]
Abstract
Interactions between MADS box transcription factors are critical in the regulation of floral development, and shifting MADS box protein-protein interactions are predicted to have influenced floral evolution. However, precisely how evolutionary variation in protein-protein interactions affects MADS box protein function remains unknown. To assess the impact of changing MADS box protein-protein interactions on transcription factor function, we turned to the grasses, where interactions between B-class MADS box proteins vary. We tested the functional consequences of this evolutionary variability using maize (Zea mays) as an experimental system. We found that differential B-class dimerization was associated with subtle, quantitative differences in stamen shape. In contrast, differential dimerization resulted in large-scale changes to downstream gene expression. Differential dimerization also affected B-class complex composition and abundance, independent of transcript levels. This indicates that differential B-class dimerization affects protein degradation, revealing an important consequence for evolutionary variability in MADS box interactions. Our results highlight complexity in the evolution of developmental gene networks: changing protein-protein interactions could affect not only the composition of transcription factor complexes but also their degradation and persistence in developing flowers. Our results also show how coding change in a pleiotropic master regulator could have small, quantitative effects on development.
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Affiliation(s)
- María Jazmín Abraham-Juárez
- Biology Department, University of Massachusetts, Amherst, 01003 Massachusetts
- CONACYT-Instituto Potosino de Investigación Científica y Tecnológica A.C., 78216 San Luis Potosi, Mexico
| | - Amanda Schrager-Lavelle
- Biology Department, University of Massachusetts, Amherst, 01003 Massachusetts
- Biology Department, Colorado Mesa University, Grand Junction, 81501 Colorado
| | - Jarrett Man
- Biology Department, University of Massachusetts, Amherst, 01003 Massachusetts
| | - Clinton Whipple
- Biology Department, Brigham Young University, Provo, 84602 Utah
| | - Pubudu Handakumbura
- Biology Department, University of Massachusetts, Amherst, 01003 Massachusetts
- Pacific Northwest National Laboratory, Richland, 99354 Washington
| | - Courtney Babbitt
- Biology Department, University of Massachusetts, Amherst, 01003 Massachusetts
| | - Madelaine Bartlett
- Biology Department, University of Massachusetts, Amherst, 01003 Massachusetts
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7
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Couturier L, Mazouni K, Corson F, Schweisguth F. Regulation of Notch output dynamics via specific E(spl)-HLH factors during bristle patterning in Drosophila. Nat Commun 2019; 10:3486. [PMID: 31375669 PMCID: PMC6677740 DOI: 10.1038/s41467-019-11477-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Accepted: 07/03/2019] [Indexed: 12/13/2022] Open
Abstract
The stereotyped arrangement of sensory bristles on the adult fly thorax arises from a self-organized process, in which inhibitory Notch signaling both delimits proneural stripes and singles out sensory organ precursor cells (SOPs). A dynamic balance between proneural factors and Enhancer of split-HLH (E(spl)-HLH) Notch targets underlies patterning, but how this is regulated is unclear. Here, were identify two classes of E(spl)-HLH factors, whose expression both precedes and delimits proneural activity, and is dependent on proneural activity and required for proper SOP spacing within the stripes, respectively. These two classes are partially redundant, since a member of the second class, that is normally cross-repressed by members of the first class, can functionally compensate for their absence. The regulation of specific E(spl)-HLH genes by proneural factors amplifies the response to Notch as SOPs are being selected, contributing to patterning dynamics in the notum, and likely operates in other developmental contexts. The patterning of sensory bristles on the dorsal thorax of flies is regulated by two transcription factor families but the dynamics of this regulation is unclear. Here, the authors visualize seven E(spl)-HLH proteins, showing their regulated expression promotes mutual inhibition by Notch during notum patterning.
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Affiliation(s)
- Lydie Couturier
- Department of Developmental and Stem Cell Biology, Institut Pasteur, 75015, Paris, France.,CNRS, UMR3738, 75015, Paris, France
| | - Khalil Mazouni
- Department of Developmental and Stem Cell Biology, Institut Pasteur, 75015, Paris, France.,CNRS, UMR3738, 75015, Paris, France
| | - Francis Corson
- Laboratoire de Physique de l'Ecole Normale Supérieure, CNRS, Sorbonne Université, Université Paris Diderot, 75005, Paris, France
| | - François Schweisguth
- Department of Developmental and Stem Cell Biology, Institut Pasteur, 75015, Paris, France. .,CNRS, UMR3738, 75015, Paris, France.
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8
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Hardwick LJA, Davies JD, Philpott A. Multi-site phosphorylation controls the neurogenic and myogenic activity of E47. Biochem Biophys Res Commun 2019; 511:111-116. [PMID: 30773262 PMCID: PMC6405440 DOI: 10.1016/j.bbrc.2019.02.045] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2019] [Accepted: 02/08/2019] [Indexed: 11/17/2022]
Abstract
The superfamily of basic-Helix-Loop-Helix (bHLH) transcription factors influence cell fate in all three embryonic germ layers, and the tissue-specific class II factors have received prominent attention for their potent ability to direct differentiation during development and in cellular reprogramming. The activity of many class II bHLH proteins driving differentiation, and the inhibitory class VI bHLH factor Hes1, is controlled by phosphorylation on multiple sites by Cyclin-dependent kinases (Cdks). As class II proteins are generally thought to be active through hetero-dimerisation with the ubiquitously expressed class I E proteins, regulation of class I transcription factors such as E47 may influence the activity of multiple tissue-specific bHLH proteins. Using differentiation of nerve and muscle in Xenopus frog embryos as a model system, we set out to explore whether with the ubiquitously expressed class I E protein E47 that hetero-dimerises with Class II bHLHs to control their activity, is also regulated by multi-site phosphorylation. We demonstrate that E47 can be readily phosphorylated by Cdks on multiple sites in vitro, while ectopically-expressed E47 exists in multiple phosphorylated forms in Xenopus embryos. Preventing multi-site phosphorylation using a phospho-mutant version of E47 enhances the neurogenic and myogenic activity of three different class II bHLH reprogramming factors, and also when E47 acts in hetero-dimerisation with endogenous proteins. Mechanistically, unlike phospho-regulation of class II bHLH factors, we find that preventing phosphorylation of E47 increases the amount of chromatin-bound E47 protein but without affecting its overall protein stability. Thus, multi-site phosphorylation is a conserved regulatory mechanism across the bHLH superfamily that can be manipulated to enhance cellular differentiation. E47 is phosphorylated in Xenopus embryos on up to 13 conserved SP/TP sites. In vitro, E47 protein can be phosphorylated by Cyclin-dependent-kinases. Under-phosphorylated E47 enhances activity of 3 bHLH reprogramming factors. Under-phosphorylated E47 enhances neuronal differentiation by hetero-dimerisation. E47 phospho-status alters chromatin binding but not overall protein stability.
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Affiliation(s)
- Laura J A Hardwick
- Department of Oncology, University of Cambridge, Hutchison/MRC Research Centre, Cambridge Biomedical Campus, Cambridge, CB2 0XZ, UK; Peterhouse, University of Cambridge, Trumpington Street, Cambridge, CB2 1RD, UK.
| | - John D Davies
- Department of Oncology, University of Cambridge, Hutchison/MRC Research Centre, Cambridge Biomedical Campus, Cambridge, CB2 0XZ, UK; Wellcome Trust/MRC Cambridge Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QR, UK.
| | - Anna Philpott
- Department of Oncology, University of Cambridge, Hutchison/MRC Research Centre, Cambridge Biomedical Campus, Cambridge, CB2 0XZ, UK; Wellcome Trust/MRC Cambridge Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QR, UK.
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9
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N-terminal phosphorylation of xHes1 controls inhibition of primary neurogenesis in Xenopus. Biochem Biophys Res Commun 2018; 509:557-563. [PMID: 30600182 PMCID: PMC6363968 DOI: 10.1016/j.bbrc.2018.12.135] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Accepted: 12/18/2018] [Indexed: 11/23/2022]
Abstract
The processes of cell proliferation and differentiation are intimately linked during embryogenesis, and the superfamily of (basic) Helix-Loop-Helix (bHLH) transcription factors play critical roles in these events. For example, neuronal differentiation is promoted by class II bHLH proneural proteins such as Ngn2 and Ascl1, while class VI Hes proteins act to restrain differentiation and promote progenitor maintenance. We have previously described multi-site phosphorylation as a key regulator of tissue specific class II bHLH proteins in all three embryonic germ layers, and this enables coordination of differentiation with the cell cycle. Hes1 homologues also show analogous conserved proline directed kinase sites. Here we have used formation of Xenopus primary neurons to investigate the effects of xHes1 multi-site phosphorylation on both endogenous and ectopic proneural protein-induced neurogenesis. We find that xHes1 is phosphorylated in vivo, and preventing phosphorylation on three conserved SP/TP sites in the N terminus of the protein enhances xHes1 protein stability and repressor activity. Mechanistically, compared to wild-type xHes1, phospho-mutant xHes1 exhibits greater repression of Ngn2 transcription as well as producing a greater reduction in Ngn2 protein stability and chromatin binding. We propose that cell cycle dependent phosphorylation of class VI Hes proteins may act alongside similar regulation of class II bHLH proneural proteins to co-ordinate their activity. xHes1 is phosphorylated in Xenopus embryos on conserved N terminal SP/TP sites. In vitro, xHes1 protein can be phosphorylated by Cyclin-dependent-kinases. Under-phosphorylated xHes1 has increased protein stability relative to WT xHes1. Under-phosphorylated xHes1 has enhanced inhibitory activity during neurogenesis. xHes1 reduces Ngn2 expression, protein stability and chromatin binding.
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10
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Baker NE, Brown NL. All in the family: proneural bHLH genes and neuronal diversity. Development 2018; 145:145/9/dev159426. [PMID: 29720483 DOI: 10.1242/dev.159426] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Proneural basic Helix-Loop-Helix (bHLH) proteins are required for neuronal determination and the differentiation of most neural precursor cells. These transcription factors are expressed in vastly divergent organisms, ranging from sponges to primates. Here, we review proneural bHLH gene evolution and function in the Drosophila and vertebrate nervous systems, arguing that the Drosophila gene atonal provides a useful platform for understanding proneural gene structure and regulation. We also discuss how functional equivalency experiments using distinct proneural genes can reveal how proneural gene duplication and divergence are interwoven with neuronal complexity.
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Affiliation(s)
- Nicholas E Baker
- Department of Genetics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461 USA
| | - Nadean L Brown
- Department of Cell Biology and Human Anatomy, University of California, One Shields Avenue, Davis, CA 95616 USA
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11
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Li K, Baker NE. Regulation of the Drosophila ID protein Extra macrochaetae by proneural dimerization partners. eLife 2018; 7:33967. [PMID: 29687780 PMCID: PMC5915177 DOI: 10.7554/elife.33967] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Accepted: 03/25/2018] [Indexed: 12/13/2022] Open
Abstract
Proneural bHLH proteins are transcriptional regulators of neural fate specification. Extra macrochaetae (Emc) forms inactive heterodimers with both proneural bHLH proteins and their bHLH partners (represented in Drosophila by Daughterless). It is generally thought that varying levels of Emc define a prepattern that determines where proneural bHLH genes can be effective. We report that instead it is the bHLH proteins that determine the pattern of Emc levels. Daughterless level sets Emc protein levels in most cells, apparently by stabilizing Emc in heterodimers. Emc is destabilized in proneural regions by local competition for heterodimer formation by proneural bHLH proteins including Atonal or AS-C proteins. Reflecting this post-translational control through protein stability, uniform emc transcription is sufficient for almost normal patterns of neurogenesis. Protein stability regulated by exchanges between bHLH protein dimers could be a feature of bHLH-mediated developmental events.
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Affiliation(s)
- Ke Li
- Department of Genetics, Albert Einstein College of Medicine, Bronx, United States
| | - Nicholas E Baker
- Department of Genetics, Albert Einstein College of Medicine, Bronx, United States.,Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, United States.,Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, United States
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12
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Subcellular localisation modulates ubiquitylation and degradation of Ascl1. Sci Rep 2018; 8:4625. [PMID: 29545540 PMCID: PMC5854709 DOI: 10.1038/s41598-018-23056-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Accepted: 03/01/2018] [Indexed: 12/31/2022] Open
Abstract
The proneural transcription factor Ascl1 is a master regulator of neurogenesis, coordinating proliferation and differentiation in the central nervous system. While its expression is well characterised, post-translational regulation is much less well understood. Here we demonstrate that a population of chromatin-bound Ascl1 can be found associated with short chains of ubiquitin while cytoplasmic Ascl1 harbours much longer ubiquitin chains. Only cytoplasmic ubiquitylation targets Ascl1 for destruction, which occurs by conjugation of ubiquitin to lysines in the basic helix-loop-helix domain of Ascl1 and requires the E3 ligase Huwe1. In contrast, chromatin-bound Ascl1 associated with short ubiquitin-chains, which can occur on lysines within the N-terminal region or the bHLH domain and is not mediated by Huwe1, is not targeted for ubiquitin-mediated destruction. We therefore offer further insights into post-translational regulation of Ascl1, highlighting complex regulation of ubiquitylation and degradation in the cytoplasm and on chromatin.
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Miesfeld JB, Glaser T, Brown NL. The dynamics of native Atoh7 protein expression during mouse retinal histogenesis, revealed with a new antibody. Gene Expr Patterns 2018; 27:114-121. [PMID: 29225067 PMCID: PMC5835195 DOI: 10.1016/j.gep.2017.11.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Revised: 11/17/2017] [Accepted: 11/28/2017] [Indexed: 12/19/2022]
Abstract
The Atoh7 transcription factor catalyzes the rate-limiting step in the specification of retinal ganglion cells (RGCs). As a tool to study vertebrate retinal development, we validate an antibody that recognizes human and mouse Atoh7 polypeptide, using informative knockout and transgenic mouse tissues and overexpression experiments. The transient features of Atoh7 protein expression during retinal neurogenesis match the expected pattern at the tissue and cellular level. Further, we compare endogenous Atoh7 to established RGC markers, reporter mouse lines and cell cycle markers, demonstrating the utility of the antibody to investigate molecular mechanisms of retinal histogenesis.
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Affiliation(s)
- Joel B Miesfeld
- Department of Cell Biology & Human Anatomy, University of California, Davis School of Medicine, One Shields Avenue, Davis, CA 95616, United States
| | - Tom Glaser
- Department of Cell Biology & Human Anatomy, University of California, Davis School of Medicine, One Shields Avenue, Davis, CA 95616, United States
| | - Nadean L Brown
- Department of Cell Biology & Human Anatomy, University of California, Davis School of Medicine, One Shields Avenue, Davis, CA 95616, United States.
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14
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Weinberger S, Topping MP, Yan J, Claeys A, Geest ND, Ozbay D, Hassan T, He X, Albert JT, Hassan BA, Ramaekers A. Evolutionary changes in transcription factor coding sequence quantitatively alter sensory organ development and function. eLife 2017; 6. [PMID: 28406397 PMCID: PMC5432213 DOI: 10.7554/elife.26402] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 03/27/2017] [Indexed: 11/16/2022] Open
Abstract
Animals are characterized by a set of highly conserved developmental regulators. Changes in the cis-regulatory elements of these regulators are thought to constitute the major driver of morphological evolution. However, the role of coding sequence evolution remains unresolved. To address this question, we used the Atonal family of proneural transcription factors as a model. Drosophila atonal coding sequence was endogenously replaced with that of atonal homologues (ATHs) at key phylogenetic positions, non-ATH proneural genes, and the closest homologue to ancestral proneural genes. ATHs and the ancestral-like coding sequences rescued sensory organ fate in atonal mutants, in contrast to non-ATHs. Surprisingly, different ATH factors displayed different levels of proneural activity as reflected by the number and functionality of sense organs. This proneural potency gradient correlated directly with ATH protein stability, including in response to Notch signaling, independently of mRNA levels or codon usage. This establishes a distinct and ancient function for ATHs and demonstrates that coding sequence evolution can underlie quantitative variation in sensory development and function. DOI:http://dx.doi.org/10.7554/eLife.26402.001
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Affiliation(s)
- Simon Weinberger
- VIB Center for the Biology of Disease, VIB, Leuven, Belgium.,Center for Human Genetics, University of Leuven School of Medicine, Leuven, Belgium.,Program in Molecular and Developmental Genetics, Doctoral School for Biomedical Sciences, University of Leuven School Group Biomedicine, Leuven, Belgium
| | - Matthew P Topping
- Ear Institute, University College London, London, United Kingdom.,Centre for Mathematics and Physics in the Life Sciences and Experimental Biology (CoMPLEX), University College London, London, United Kingdom
| | - Jiekun Yan
- VIB Center for the Biology of Disease, VIB, Leuven, Belgium.,Center for Human Genetics, University of Leuven School of Medicine, Leuven, Belgium
| | - Annelies Claeys
- VIB Center for the Biology of Disease, VIB, Leuven, Belgium.,Center for Human Genetics, University of Leuven School of Medicine, Leuven, Belgium
| | - Natalie De Geest
- VIB Center for the Biology of Disease, VIB, Leuven, Belgium.,Center for Human Genetics, University of Leuven School of Medicine, Leuven, Belgium
| | - Duru Ozbay
- VIB Center for the Biology of Disease, VIB, Leuven, Belgium.,Center for Human Genetics, University of Leuven School of Medicine, Leuven, Belgium
| | - Talah Hassan
- Ear Institute, University College London, London, United Kingdom
| | - Xiaoli He
- Ear Institute, University College London, London, United Kingdom
| | - Joerg T Albert
- Ear Institute, University College London, London, United Kingdom.,Centre for Mathematics and Physics in the Life Sciences and Experimental Biology (CoMPLEX), University College London, London, United Kingdom.,Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Bassem A Hassan
- VIB Center for the Biology of Disease, VIB, Leuven, Belgium.,Center for Human Genetics, University of Leuven School of Medicine, Leuven, Belgium.,Program in Molecular and Developmental Genetics, Doctoral School for Biomedical Sciences, University of Leuven School Group Biomedicine, Leuven, Belgium.,Institut du Cerveau et de la Moelle Epinière (ICM) - Hôpital Pitié-Salpêtrière, UPMC, Sorbonne Universités, Inserm, CNRS, Paris, France
| | - Ariane Ramaekers
- VIB Center for the Biology of Disease, VIB, Leuven, Belgium.,Center for Human Genetics, University of Leuven School of Medicine, Leuven, Belgium.,Institut du Cerveau et de la Moelle Epinière (ICM) - Hôpital Pitié-Salpêtrière, UPMC, Sorbonne Universités, Inserm, CNRS, Paris, France
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15
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Abstract
Building a nervous system requires a precise sequence of genetic transitions, mediated in part by the temporal and spatial regulation of transcription factors. Quan et al. add to our understanding of this regulation by describing an evolutionarily conserved post-translational mechanism that rapidly extinguishes proneural protein activity in neural precursors.
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Affiliation(s)
- Richard S Mann
- Departments of Biochemistry and Molecular Biophysics and Systems Biology, Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA.
| | - Clare E Howard
- Department of Biochemistry and Molecular Biophysics, Zuckerman Mind Brain Behavior Institute, Medical Scientist Training Program, Columbia University, New York, NY 10027, USA
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16
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Wang LH, Baker NE. E Proteins and ID Proteins: Helix-Loop-Helix Partners in Development and Disease. Dev Cell 2016; 35:269-80. [PMID: 26555048 DOI: 10.1016/j.devcel.2015.10.019] [Citation(s) in RCA: 110] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 10/18/2015] [Accepted: 10/23/2015] [Indexed: 01/12/2023]
Abstract
The basic Helix-Loop-Helix (bHLH) proteins represent a well-known class of transcriptional regulators. Many bHLH proteins act as heterodimers with members of a class of ubiquitous partners, the E proteins. A widely expressed class of inhibitory heterodimer partners-the Inhibitor of DNA-binding (ID) proteins-also exists. Genetic and molecular analyses in humans and in knockout mice implicate E proteins and ID proteins in a wide variety of diseases, belying the notion that they are non-specific partner proteins. Here, we explore relationships of E proteins and ID proteins to a variety of disease processes and highlight gaps in knowledge of disease mechanisms.
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Affiliation(s)
- Lan-Hsin Wang
- Department of Genetics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
| | - Nicholas E Baker
- Department of Genetics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA; Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA; Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
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