Smad1 and Smad4 are components of the bone morphogenetic protein-4 (BMP-4)-induced transcription complex of the Xvent-2B promoter.
To study the mechanism of transcriptional activation of the Xenopus homeobox gene Xvent-2B, we have delineated the bone morphogenetic protein-4 (BMP-4)-responsive region between -275/-152 in the proximal promoter. Consistent with the BMP-4 inductive nature of this region, this element exhibits transcriptional activation upon ectopic expression of Smad1 and Smad4. Electrophoretic mobility shift assays with total cellular extracts demonstrated that a DNA fragment encompassing this region was competent in the formation of a BMP-4-induced protein-DNA complex containing Smad1. Two different Smad binding regions were localized, a distal binding region for Smad1 containing two GCAT motifs and proximal AGNC binding sites for Smad4, the latter being conserved in other transforming growth factor-beta-responsive elements. Mutation of the Smad4 binding motif completely abolished transcriptional activation, whereas mutation or deletion of the Smad1 recognition sequence inhibited Smad1/Smad4 responsiveness. These results provide a functional characterization and identification of a vertebrate Smad1/Smad4 DNA response element induced by BMP-4 signaling and offers insight into the transcriptional regulation of a component essential for dorsoventral patterning in Xenopus embryos.
Henningfeld
K A
KA
Abt. Biochemie and Abt. Innere Medizin I, Universität Ulm, Albert-Einstein Allee 11, 89081 Ulm, Germany.
Rastegar
S
S
Adler
G
G
Knöchel
W
W
D000818:Animals; D001483:Base Sequence; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics*; D018398:Homeodomain Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D009414:Nerve Growth Factors; D011401:Promoter Regions, Genetic; D051785:Smad Proteins; D051901:Smad4 Protein; D015534:Trans-Activators / Q000235:genetics*; D014157:Transcription Factors; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014981:Xenopus; D029867:Xenopus Proteins
D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; C497402:MXD1 protein, Xenopus; D009414:Nerve Growth Factors; D051785:Smad Proteins; D051901:Smad4 Protein; D015534:Trans-Activators; D014157:Transcription Factors; D029867:Xenopus Proteins; C525812:bmp4 protein, Xenopus; C490808:smad4.1 protein, Xenopus; C117263:smad4.2 protein, Xenopus; C099992:ventx2.1 protein, Xenopus