title: Drosophila CK2 phosphorylates Deadpan, a member of the HES family of basic-helix-loop-helix (bHLH) repressors.
abstract: In Drosophila, protein kinase CK2 regulates a diverse array of developmental processes. One of these is cell-fate specification (neurogenesis) wherein CK2 regulates basic-helix-loop-helix (bHLH) repressors encoded by the Enhancer of Split Complex (E(spl)C). Specifically, CK2 phosphorylates and activates repressor functions of E(spl)M8 during eye development. In this study we describe the interaction of CK2 with an E(spl)-related bHLH repressor, Deadpan (Dpn). Unlike E(spl)-repressors which are expressed in cells destined for a non-neural cell fate, Dpn is expressed in the neuronal cells and is thought to control the activity of proneural genes. Dpn also regulates sex-determination by repressing sxl, the primary gene involved in sex differentiation. We demonstrate that Dpn is weakly phosphorylated by monomeric CK2alpha, whereas it is robustly phosphorylated by the embryo-holoenzyme, suggesting a positive role for CK2beta. The weak phosphorylation by CK2alpha is markedly stimulated by the activator polylysine to levels comparable to those with the holoenzyme. In addition, pull down assays indicate a direct interaction between Dpn and CK2. This is the first demonstration that Dpn is a partner and target of CK2, and raises the possibility that its repressor functions might also be regulated by phosphorylation.
authors.affiliation: Department of Biology, West Virginia University, Morgantown, WV 26506-6057, USA.
authors.forename: Umesh C
authors.initials: UC
authors.lastname: Karandikar
authors.forename: Jonathan
authors.initials: J
authors.lastname: Shaffer
authors.forename: Clifton P
authors.initials: CP
authors.lastname: Bishop
authors.forename: Ashok P
authors.initials: AP
authors.lastname: Bidwai
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000737:chemistry*; D047390:Casein Kinase II / Q000737:chemistry*; D020134:Catalytic Domain; D017124:Conserved Sequence; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry*; D010766:Phosphorylation; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D020798:Two-Hybrid System Techniques
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D047390:Casein Kinase II; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; C078020:Dpn protein, Drosophila