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Xvent‐1 mediates BMP‐4‐induced suppression of the dorsal‐lip‐specific early response gene XFD‐1′ in Xenopus embryos
Author(s) -
Friedle Henner,
Rastegar Sepand,
Paul Hubert,
Kaufmann Eckhard,
Knöchel Walter
Publication year - 1998
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/17.8.2298
Subject(s) - allee effect , biology , sociology , demography , population
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.