Format

Send to

Choose Destination
Proc Natl Acad Sci U S A. 1998 May 12;95(10):5626-31.

Wnt signaling and transcriptional control of Siamois in Xenopus embryos.

Author information

1
Department of Microbiology and Molecular Genetics, Harvard Medical School, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215, USA.

Abstract

The Wnt-inducible homeobox gene Siamois is expressed in Xenopus embryos before gastrulation and is necessary for formation of the Spemann organizer. Here we show that 5'-flanking sequences of the Siamois coding region can specifically activate a heterologous reporter gene in dorsovegetal cells, thus mimicking Siamois's endogenous expression. A 245-bp DNA fragment is sufficient for activation by both Wnts and endogenous inducers. A dominant negative form of Xenopus T cell-specific factor 3 (XTCF-3) inhibited promoter activity, indicating that T cell-specific factor (TCF)/lymphocyte enhancer binding factor 1 (LEF-1) signaling is necessary for regulation of Siamois. Mutagenesis of two individual TCF sites in the -245 promoter revealed that the proximal, but not distal, site is necessary for dorsovegetal activation. These observations suggest that Siamois is directly regulated by TCFs during dorsoventral axis determination. Further deletion analysis identified a positive regulatory region that is required for dorsal activation, but not for Wnt inducibility, of the promoter. We also present evidence for autoregulation of Siamois transcription. Furthermore, the Siamois promoter was activated by Wnt signaling in 293T tissue culture cells, demonstrating that regulation of the promoter is functionally conserved.

PMID:
9576934
PMCID:
PMC20429
DOI:
10.1073/pnas.95.10.5626
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for HighWire Icon for PubMed Central
Loading ...
Support Center