Xvent-1 mediates BMP-4-induced suppression of the dorsal-lip-specific early response gene XFD-1′ in Xenopus embryos

• Published in: The EMBO journal 1998-04, Vol.17 (8), p.2298-2307
• Main Authors: Friedle, Henner, Rastegar, Sepand, Paul, Hubert, Kaufmann, Eckhard, Knöchel, Walter
• Format: Article
• Language: English
• Subjects: Animals; Base Sequence; Binding Sites; BMP-4 signalling; Bone Morphogenetic Protein 4; Bone Morphogenetic Proteins - genetics; Bone Morphogenetic Proteins - metabolism; DNA; DNA-Binding Proteins - genetics; Freshwater; Gene Expression Regulation, Developmental; Homeodomain Proteins - genetics; mesoderm; Molecular Sequence Data; Mutagenesis; Repressor Proteins - genetics; Smad Proteins; Spemann organizer; Trans-Activators; transcription factors; Transcription, Genetic; Xenopus; Xenopus laevis - embryology; Xenopus Proteins
• ISSN: 0261-4189; 1460-2075; 1460-2075
• DOI: 10.1093/emboj/17.8.2298

Ectopic expression of the ventralizing morphogen BMP‐4 (bone morphogenetic protein‐4) in the dorsal lip (Spemann organizer) of Xenopus embryos blocks transcription of dorsal‐lip‐specific early response genes. We investigated the molecular mechanism underlying the BMP‐4‐induced inhibition of the fork head gene XFD‐1′ . The promoter of this gene contains a BMP‐triggered inhibitory element (BIE) which prevents activation of this gene at the ventral/vegetal side of the embryo in vivo . In the present study, we show that BMP‐4‐induced inhibition is not direct but indirect, and is mediated by Xvent homeobox proteins. Micro‐injections of Xvent‐1 RNA and XFD‐1′ promoter deletion mutants demonstrate that Xvent‐1 mimics the effect of BMP‐4 signalling not only by suppression of the XFD‐1′ gene, but also by utilizing the BIE. Suppression could be reverted using a dominant‐negative Xvent‐1 mutant. The repressor domain was localized to the N‐terminal region of the protein. Gel‐shift and footprint analyses prove that Xvent‐1 binds to the BIE. Moreover, PCR‐based target‐site selection for the Xvent‐1 homeodomain confirms distinct motifs within the BIE as preferential binding sites. Thus, biological and molecular data suggest that Xvent‐1 acts as direct repressor for XFD‐1′ transcription and mediates BMP‐4‐induced inhibition.