Schnurri mediates Dpp-dependent repression of brinker transcription.
Signalling by Decapentaplegic (Dpp), a member of the TGFbeta superfamily of signalling molecules, controls many aspects of Drosophila development by activating and repressing target genes. Several essential components of the Dpp signalling pathway have been identified, including the Dpp receptors Punt and Thick veins (Tkv) as well as the cytoplasmic mediators Mad and Medea. For target genes to be activated, Dpp signalling must suppress transcription of a repressor encoded by the brinker (brk) gene. Here we show that Schnurri (Shn), a large zinc-finger protein, is essential for Dpp-mediated repression of brk transcription; in contrast, Shn is not required for target-gene activation. Thus, the Dpp signalling pathway bifurcates, downstream of the signal-mediating SMAD proteins, into a Shn-dependent pathway leading to brk repression and a Shn-independent pathway leading to gene activation. The existence of several Shn-like proteins in vertebrates and the observation that Brk functions in BMP signalling in Xenopus indicates that a similar regulatory cascade may be conserved in higher organisms.
Marty
T
T
Abteilung Zellbiologie, Biozentrum, Universität Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland.
Müller
B
B
Basler
K
K
Affolter
M
M
D000818:Animals; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004330:Drosophila / Q000196:embryology; D029721:Drosophila Proteins; D018507:Gene Expression Regulation, Developmental; D019476:Insect Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism*; D008957:Models, Genetic; D012097:Repressor Proteins / Q000096:biosynthesis* / Q000235:genetics; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D016212:Transforming Growth Factor beta / Q000378:metabolism
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D019476:Insect Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; C118082:brk protein, Drosophila; C064196:dpp protein, Drosophila; C094066:shn protein, Drosophila