XB-ART-3507Differentiation April 1, 2004; 72 (4): 171-84.
Early endodermal expression of the Xenopus Endodermin gene is driven by regulatory sequences containing essential Sox protein-binding elements.
The Endodermin gene is expressed in the early endoderm and the Spemann organizer of Xenopus embryos. It has previously been shown to be a direct target of the early endodermal transcription factor Xsox17 (Clements et al., 2003, Mech Dev 120:337-348). Here we identify two adjacent control elements in the Endodermin promoter; these drive transcription of the gene in late-gastrula endoderm and contain consensus Sox-binding sites. We have analyzed one element in detail and show that it responds directly to Xsox17 and that the Sox sites are essential for endodermal expression in transgenic embryos. However, flanking regions on both sides are also essential, indicating that Xsox17 acts in concert with several DNA-binding partners.
PubMed ID: 15157240
Article link: Differentiation
Genes referenced: a2m actc1 sox17a tbx2
Article Images: [+] show captions
|Fig. 3 Two promoter fragments, E1 and E2, contain putative Soxbinding sites and can drive gastrula-stage expression in the endoderm. The position of the two Pst1/Spe1 fragments, E1 and E2, are shown at the top. Their expression in partial transgenics is shown below, using GFP fluorescence and in situ hybridization to GFP mRNA in different embryos. On the right are shown the sequences of E and E2, indicating Sox-binding sites (yellow boxes, contained the core sequence ACAAT), Smad sites (green), FAST-1 sites (blue), and GATA sites (red). The three Sox sites in E2, of which the central one is a complex of three overlapping sites, are labelled A–C.|
|Fig. 6 (1) Site B is necessary but not sufficient for endoderm expression of E2:112. In each case, the constructs are shown on the left and GFP expression by fluorescence or in situ is shown on the right. (A, B) Endodermal expression of E2:112. (C–F) Reporter constructs containing site B, with either a 2 or 10 bp flanking sequence on either side, were not sufficient for endoderm expression. (G, H) Deletion of site B from E2:112 abolished reporter expression in the endoderm. (I–L) Endodermal expression was not restored in reporter constructs containing site B together with upstream or downstream sequences (I–L). (2) The reporter construct E2:112 is vegetally induced, but only if the B Sox site is present. Without this site, Xsox17b represses luciferase expression, but the B Sox site relieves this. The constructs are indicated.|