Fig. 1. Structure of Xfz3 and Xfz7 derivatives used in this study. The myc-tagged proteins contain six myc epitopes inserted at the N-terminus immediately after the peptide signal. The flag and HA tags are located at the C-terminus end of the proteins. Xfz3-C-myc corresponds to Xfz3 but retains only five amino acids after the seventh transmembrane domain (Umbhauer et al., 2000a). Extra3-myc and extra3-flag correspond to the 196 first amino acids of Xfz3 bearing myc and flag tags, respectively. Extra3-R1 is a chimeric receptor in which the 196 N-terminal amino acids of Xfz3 are fused with the transmembrane and cytoplasmic domains of FGFR-1 (Musci et al., 1990). Xfz3C-R1 corresponds to the first 505 N-terminal amino acids of Xfz3 fused with the cytoplasmic domain of FGFR-1. Xf7C-flag corresponds to Xfz7 truncated immediately after the seventh transmembrane domain at residue 525. In Xfz7-BD, the CRD of Xfz7 is swapped with the oligomerization domain (B domain) of the ETS protein, TEL (Lopez et al., 1999).