Click here to close Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly. We suggest using a current version of Chrome, FireFox, or Safari.
Dev Biol October 15, 1999; 214 (2): 354-69.

Xenopus Smad4beta is the co-Smad component of developmentally regulated transcription factor complexes responsible for induction of early mesodermal genes.

Howell M , Itoh F , Pierreux CE , Valgeirsdottir S , Itoh S , ten Dijke P , Hill CS .

Smad4 is defined as the common-mediator Smad (co-Smad) required for transducing signals for all TGF-beta superfamily members. This paper describes two Smad4s in Xenopus: XSmad4alpha, which is probably the Xenopus orthologue of human Smad4, and a distinct family member, XSmad4beta, which differs primarily at the extreme N-terminus and in the linker region. Both XSmad4s act as co-Smads, forming ligand-dependent complexes with receptor-regulated Smads 1 and 2 and synergizing with them to activate transcription of mesodermal genes in Xenopus embryos. The two XSmad4 genes have reciprocal temporal expression patterns in Xenopus embryos and are expressed in varying ratios in adult tissues, suggesting distinct functional roles in vivo. XSmad4beta is the predominant maternal co-Smad and we go on to demonstrate its role in the transcriptional regulation of early mesodermal genes. We have identified two distinct nuclear complexes that bind the activin-responsive element of the Xenopus Mix.2 promoter: one formed in response to high levels of activin signaling and the other activated by endogenous signaling pathways. Using specific antisera we demonstrate the presence of endogenous XSmad4beta and also XSmad2 in both of these complexes, and our data indicate that the DNA-binding components of the complexes are different. Furthermore, we show that the presence of these complexes in the nucleus perfectly correlates with the transcriptional activity of the target gene, Mix.2, and we show that one of the XSmad4beta-containing transcription factor complexes undergoes a developmentally regulated nuclear translocation.

PubMed ID: 10525340
Article link: Dev Biol

Genes referenced: smad2 smad4.1 smad4.2

Xenbase: The Xenopus Model Organism Knowledgebase.
Version: 4.15.0
Major funding for Xenbase is provided by grant P41 HD064556