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      Delta activity independent of its activity as a ligand of Notch

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          Abstract

          Background

          Delta, Notch, and Scabrous often function together to make different cell types and refine tissue patterns during Drosophila development. Delta is known as the ligand that triggers Notch receptor activity. Scabrous is known to bind Notch and promote Notch activity in response to Delta. It is not known if Scabrous binds Delta or Delta has activity other than its activity as a ligand of Notch. It is very difficult to clearly determine this binding or activity in vivo as all Notch, Delta, and Scabrous activities are required simultaneously or successively in an inter-dependent manner.

          Results

          Using Drosophila cultured cells we show that the full length Delta promotes accumulation of Daughterless protein, fringe RNA, and pangolin RNA in the absence of Scabrous or Notch. Scabrous binds Delta and suppresses this activity even though it increases the level of the Delta intracellular domain. We also show that Scabrous can promote Notch receptor activity, in the absence of Delta.

          Conclusion

          Delta has activity that is independent of its activity as a ligand of Notch. Scabrous suppresses this Delta activity. Scabrous also promotes Notch activity that is dependent on Delta's ligand activity. Thus, Notch, Delta, and Scabrous might function in complex combinatorial or mutually exclusive interactions during development. The data reported here will be of significant help in understanding these interactions in vivo.

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          Most cited references53

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          Armadillo coactivates transcription driven by the product of the Drosophila segment polarity gene dTCF.

          The vertebrate transcription factors TCF (T cell factor) and LEF (lymphocyte enhancer binding factor) interact with beta-catenin and are hypothesized to mediate Wingless/Wnt signaling. We have cloned a maternally expressed Drosophila TCF family member, dTCF. dTCF binds a canonical TCF DNA motif and interacts with the beta-catenin homolog Armadillo. Previous studies have identified two regions in Armadillo required for Wingless signaling. One of these interacts with dTCF, while the other constitutes a transactivation domain. Mutations in dTCF and expression of a dominant-negative dTCF transgene cause a segment polarity phenotype and affect expression of the Wingless target genes engrailed and Ultrabithorax. Epistasis analysis positions dTCF downstream of armadillo. The Armadillo-dTCF complex mediates Wingless signaling as a bipartite transcription factor.
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            • Record: found
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            Notch signaling: from the outside in.

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              Fringe is a glycosyltransferase that modifies Notch.

              Notch receptors function in highly conserved intercellular signalling pathways that direct cell-fate decisions, proliferation and apoptosis in metazoans. Fringe proteins can positively and negatively modulate the ability of Notch ligands to activate the Notch receptor. Here we establish the biochemical mechanism of Fringe action. Drosophila and mammalian Fringe proteins possess a fucose-specific beta1,3 N-acetylglucosaminyltransferase activity that initiates elongation of O-linked fucose residues attached to epidermal growth factor-like sequence repeats of Notch. We obtained biological evidence that Fringe-dependent elongation of O-linked fucose on Notch modulates Notch signalling by using co-culture assays in mammalian cells and by expression of an enzymatically inactive Fringe mutant in Drosophila. The post-translational modification of Notch by Fringe represents a striking example of modulation of a signalling event by differential receptor glycosylation and identifies a mechanism that is likely to be relevant to other signalling pathways.
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                Author and article information

                Journal
                BMC Dev Biol
                BMC Developmental Biology
                BioMed Central (London )
                1471-213X
                2005
                10 March 2005
                : 5
                : 6
                Affiliations
                [1 ]Department of Microbiology and Molecular Genetics, 322 Stafford Hall, 95 Carrigan Drive, The University of Vermont, Burlington, VT 05405, USA
                [2 ]Rollins School of Public Health, Emory University, Atlanta, GA 30322, USA
                [3 ]INSERM E365, Faculte de Medecine Lariboisiere, 10 avenue de Verdun, Paris 75010, France
                [4 ]College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA
                [5 ]Department of Civil Engineering, The University of Minnesota, Minneapolis, MN 55455, USA
                Article
                1471-213X-5-6
                10.1186/1471-213X-5-6
                555533
                15760463
                c3b83c17-3f1f-4c60-9d3e-adc9c9594cba
                Copyright © 2005 Mok et al; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 15 August 2004
                : 10 March 2005
                Categories
                Research Article

                Developmental biology
                Developmental biology

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