Xvent-1 mediates BMP-4-induced suppression of the dorsal-lip-specific early response gene XFD-1' in Xenopus embryos.
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.
Friedle
H
H
Abteilung Biochemie, Universität Ulm, Albert-Einstein-Allee 11, D-89081 Ulm, Germany.
Rastegar
S
S
Paul
H
H
Kaufmann
E
E
Knöchel
W
W
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000378:metabolism; D004247:DNA; D004268:DNA-Binding Proteins / Q000235:genetics*; D051858:Forkhead Transcription Factors; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D016296:Mutagenesis; D012097:Repressor Proteins / Q000235:genetics*; D051785:Smad Proteins; D015534:Trans-Activators; D014158:Transcription, Genetic; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000196:embryology
D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D004268:DNA-Binding Proteins; D051858:Forkhead Transcription Factors; C000598904:FoxA4 protein, Xenopus; D018398:Homeodomain Proteins; D012097:Repressor Proteins; D051785:Smad Proteins; D015534:Trans-Activators; D029867:Xenopus Proteins; C525812:bmp4 protein, Xenopus; C420285:foxd4l1.1 protein, Xenopus; D004247:DNA