title: Transcriptional regulation of Xvent homeobox genes.
abstract: The Xvent homeobox multigene family is essential for the patterning of the ventral mesoderm in Xenopus embryos. We have identified two novel members of this family, Xvent-1B and Xvent-2B, and have characterized their genomic structures. These two genes show a clustered organization and have probably arisen by gene duplication with subsequent inversion. Cis-regulatory elements within the promoters of both genes have been identified which contribute to their spatial activation. Xvent-2B is activated by BMP-2/4 in the absence of de novo protein synthesis, suggesting that this gene is a direct target of BMP-signalling. In contrast, Xvent-1B does not directly respond to BMP-2/4, but is activated by Xvent-2B. This activation is documented by Xvent-1B promoter/reporter studies, Xvent-2B overexpression and loss-of-function analysis using a dominant-negative Xvent-2 mutant. However, cycloheximide experiments reveal that Xvent-2B by itself is not sufficient to activate transcription of the Xvent-1B gene, but that there is a requirement for additional factor(s) being synthesized after midblastula transition.
mesh_terms: D000595:Amino Acid Sequence; D055396:Bone Morphogenetic Protein 2; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D004843:Epistasis, Genetic; D005799:Genes, Dominant; D005809:Genes, Regulator / Q000502:physiology*; D015698:Genomic Library; D018398:Homeodomain Proteins / Q000235:genetics*; D017403:In Situ Hybridization; D008156:Luciferases / Q000378:metabolism; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010641:Phenotype; D011401:Promoter Regions, Genetic; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011993:Recombinant Fusion Proteins; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D014018:Tissue Distribution; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D029867:Xenopus Proteins