Supplement Figure 3 SYF cells Supplement Figure 3. RET/PTC3 induces tyrosine phosphorylation of XB130 in the absence of Src tyrosine kinases. SYF cells murine embryonic fibroblasts, which lack expression of the three major Src kinases (Src, Yes and Fyn) were transfected with XB130-His, or in combination with Src-Flag and/or Ret/pts3-Myc. Protein tyrosine phosphorylation was determined by western blotting, using anti-phosphotyrosine antibody (4G10). Ret/ptc is able to phosphorylate XB130 in the absence of Src kinases. Co-expression of Ret/ptc and Src further enhanced phosphorylation of XB130.