Indirect evidence for Delta-dependent intracellular processing of notch in Drosophila embryos.
Cell-cell signaling mediated by the receptor Notch regulates the differentiation of a wide variety of cell types in invertebrate and vertebrate species, but the mechanism of signal transduction following receptor activation is unknown. A recent model proposes that ligand binding induces intracellular processing of Notch; the processed intracellular form of Notch then translocates to the nucleus and interacts with DNA-bound Suppressor of Hairless (Su(H)), a transcription factor required for target gene expression. As intracellular processing of endogenous Notch has so far escaped immunodetection, we devised a sensitive nuclear-activity assay to monitor indirectly the processing of an engineered Notch in vivo. First, we show that the intracellular domain of Notch, fused to the DNA-binding domain of Gal4, regulated transcription, in a delta-independent manner. Second, we show that full-length Notch, containing the Gal4 DNA-binding domain inserted 27 amino acids carboxy-terminal to the transmembrane domain, activated transcription in a delta-dependent manner. These results provide indirect evidence for a ligand-dependent intracellular processing event in vivo, supporting the view that Su(H)-dependent Notch signaling involves intracellular cleavage, and transcriptional regulation by processed Notch.
Lecourtois
M
M
Ecole Normale Supériuer, CNRS ATIPE URA1857, Paris, France.
Schweisguth
F
F
D000818:Animals; D002450:Cell Communication; D004330:Drosophila / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D029721:Drosophila Proteins; D007424:Intracellular Fluid / Q000378:metabolism* / Q000502:physiology; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000378:metabolism* / Q000502:physiology*; D051880:Receptors, Notch; D015398:Signal Transduction
D029721:Drosophila Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C497759:N protein, Drosophila; D051880:Receptors, Notch; C064045:delta protein