title: Multiple RTK pathways downregulate Groucho-mediated repression in Drosophila embryogenesis.
abstract: RTK pathways establish cell fates in a wide range of developmental processes. However, how the pathway effector MAPK coordinately regulates the expression of multiple target genes is not fully understood. We have previously shown that the EGFR RTK pathway causes phosphorylation and downregulation of Groucho, a global co-repressor that is widely used by many developmentally important repressors for silencing their various targets. Here, we use specific antibodies that reveal the dynamics of Groucho phosphorylation by MAPK, and show that Groucho is phosphorylated in response to several RTK pathways during Drosophila embryogenesis. Focusing on the regulation of terminal patterning by the Torso RTK pathway, we demonstrate that attenuation of Groucho's repressor function via phosphorylation is essential for the transcriptional output of the pathway and for terminal cell specification. Importantly, Groucho is phosphorylated by an efficient mechanism that does not alter its subcellular localisation or decrease its stability; rather, modified Groucho endures long after MAPK activation has terminated. We propose that phosphorylation of Groucho provides a widespread, long-term mechanism by which RTK signals control target gene expression.
authors.affiliation: Department of Biochemistry, Faculty of Medicine, The Hebrew University, Jerusalem, Israel.
authors.forename: Einat
authors.initials: E
authors.lastname: Cinnamon
authors.forename: Aharon
authors.initials: A
authors.lastname: Helman
authors.forename: Rachel
authors.initials: R
authors.lastname: Ben-Haroush Schyr
authors.forename: Amir
authors.initials: A
authors.lastname: Orian
authors.forename: Gerardo
authors.initials: G
authors.lastname: Jiménez
authors.forename: Ze'ev
authors.initials: Z
authors.lastname: Paroush
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics*; D004330:Drosophila / Q000196:embryology* / Q000201:enzymology; D004625:Embryo, Nonmammalian / Q000201:enzymology / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D017403:In Situ Hybridization; D007700:Kinetics; D007814:Larva / Q000502:physiology; D054258:Neural Plate / Q000502:physiology; D010766:Phosphorylation; D010957:Plasmids; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics*
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D020794:Receptor Protein-Tyrosine Kinases; D012097:Repressor Proteins; C091023:gro protein, Drosophila