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

Academic Press 1999

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.

Activins; Molecular Sequence Data; Nerve Growth Factors; Plasmids; Protein Binding; Sequence Homology, Amino Acid; Signal Transduction; Smad Proteins; Smad2 Protein; Smad4 Protein; Time Factors; Amino Acid Sequence; Tissue Distribution; Trans-Activators; Transcription Factors; Transcription, Genetic; Transfection; Transforming Growth Factor beta; Xenopus; Xenopus Proteins; Animals; Cell Nucleus; DNA-Binding Proteins; Forkhead Transcription Factors; Gene Expression Regulation, Developmental; Inhibins; Mesoderm; info:eu-repo/semantics/article

Open access content. Open access content
info:eu-repo/semantics/restrictedAccess

English

UCDLC oai:dial.uclouvain.be:boreal:132287
boreal:132287
info:doi/10.1006/dbio.1999.9430
info:pmid/10525340
urn:ISSN:0012-1606
urn:EISSN:1095-564X
1130499425

UNIVERSITE CATHOLIQUE DE LOUVAIN
From OAIster®, provided by the OCLC Cooperative.

edsoai.on1130499425