Biochemical analysis of torso and D-raf during Drosophila embryogenesis: implications for terminal signal transduction

Mol Cell Biol. 1993 Feb;13(2):1163-72. doi: 10.1128/mcb.13.2.1163-1172.1993.

Abstract

Determination of anterior and posterior terminal structures of Drosophila embryos requires activation of two genes encoding putative protein kinases, torso and D-raf. In this study, we demonstrate that Torso has intrinsic tyrosine kinase activity and show that it is transiently tyrosine phosphorylated (activated) at syncytial blastoderm stages. Torso proteins causing a gain-of-function phenotype are constitutively tyrosine phosphorylated, while Torso proteins causing a loss-of-function phenotype lack tyrosine kinase activity. The D-raf gene product, which is required for Torso function, is identified as a 90-kDa protein with intrinsic serine/threonine kinase activity. D-Raf is expressed throughout embryogenesis; however, the phosphorylation state of the protein changes during development. In wild-type embryos, D-Raf is hyperphosphorylated at 1 to 2 h after egg laying, and thereafter only the most highly phosphorylated form is detected. Embryos lacking Torso activity, however, show significant reductions in D-Raf protein expression rather than major alterations in the protein's phosphorylation state. This report provides the first biochemical analysis of the terminal signal transduction pathway in Drosophila embryos.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 3T3 Cells
  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • DNA
  • Drosophila / embryology
  • Drosophila / genetics*
  • Electrophoresis, Polyacrylamide Gel
  • Ligands
  • Mice
  • Molecular Sequence Data
  • Phosphorylation
  • Protein Serine-Threonine Kinases / genetics*
  • Protein-Tyrosine Kinases / genetics
  • Protein-Tyrosine Kinases / metabolism*
  • Signal Transduction / genetics*

Substances

  • Ligands
  • DNA
  • Protein-Tyrosine Kinases
  • Protein Serine-Threonine Kinases