Fig. 7. Xsix3 directly represses Bmp4 transcription. (A,B) Animal caps were analysed at stage 13 for the expression of the genes indicated to the left. (A) Bmp4 repression in GR-Xsix3-injected animal caps treated either with dexamethasone (DEX) alone, or with both DEX and cycloheximide (CHX), compare with control with no DEX treatment shown above. (B) Control of CHX treatment. Xotx2-GR-injected animal caps treated with DEX alone, or with both DEX and CHX. (C) Xsix3 binds to a Bmp4 promoter fragment containing homeodomain-binding sites. Xsix3-GST, but not GST alone, binds to the labelled Bmp4 promoter to form various complexes in a concentration-dependent manner. Addition of an excess of unlabelled Bmp4 promoter fragment (50- to 350-fold) significantly inhibits the binding. The arrow indicates the major complex formed with the highest protein concentration. The arrowhead indicates the free probe. The amount of added protein is indicated in micrograms.