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Andreas von Bubnoff

Publications and source records attributed to Andreas von Bubnoff.

10 recordsLinked to original sources
PubMed2005

Phylogenetic footprinting and genome scanning identify vertebrate BMP response elements and new target genes.

The complex gene regulatory networks governed by growth factor signaling are still poorly understood. In order to accelerate the rate of progress in uncovering these networks, we explored the usefulness of interspecies sequence comparison (phylogenetic footprinting) to identify conserved growth factor response elements. The promoter regions of two direct target genes of Bone Morphogenetic Protein (BMP) signaling in Xenopus, Xvent2 and XId3, were compared with the corresponding human and/or mouse counterparts to identify conserved sequences. A comparison between the Xenopus and human Vent2 promoter sequences revealed a highly conserved 21 bp sequence that overlaps the previously reported Xvent2 BMP response element (BRE). Reporter gene assays using Xenopus animal pole ectodermal explants (animal caps) revealed that this conserved 21 bp BRE is both necessary and sufficient for BMP responsiveness. We combine the same phylogenetic footprinting approach with luciferase assays to identify a highly conserved 49 bp BMP responsive region in the Xenopus Id3 promoter. GFP reporters containing multimers of either the Xvent2 or XId3 BREs appear to recapitulate endogenous BMP signaling activity in transgenic Xenopus embryos. Comparison of the Xvent2 and the XId3 BRE revealed core sequence features that are both necessary and sufficient for BMP responsiveness: a Smad binding element (SBE) and a GC-rich element resembling an OAZ binding site. Based on these findings, we have implemented genome scanning to identify over 100 additional putative target genes containing 2 or more BRE-like sequences which are conserved between human and mouse. RT-PCR and in situ analyses revealed that this in silico approach can effectively be used to identify potential BMP target genes.

Animals↗
PubMed2003

Tob proteins enhance inhibitory Smad-receptor interactions to repress BMP signaling.

Tob inhibits bone morphogenetic protein (BMP) signaling by interacting with receptor-regulated Smads in osteoblasts. Here we provide evidence that Tob also interacts with the inhibitory Smads 6 and 7. A yeast two-hybrid screen identified Smad6 as a protein interacting with Tob. Tob co-localizes with Smad6 at the plasma membrane and enhances the interaction between Smad6 and activated BMP type I receptors. Furthermore, we have isolated Xenopus Tob2, and show that it cooperates with Smad6 in inducing secondary axes when expressed in early Xenopus embryos. Finally, Tob and Tob2 cooperate with Smad6 to inhibit endogenous BMP signaling in Xenopus embryonic explants and in cultured mammalian cells. Our results provide both in vitro and in vivo evidence that Tob inhibits endogenous BMP signaling by facilitating inhibitory Smad functions.

Amino Acid Sequence↗