Interaction between PAI-2 and ZNF198/FGFR1. HEK-293 cells expressing ZNF198/FGFR1 (FUS) also express the 47-kDa and 32-kDa forms of PAI-2. Coimmunoprecipitation from ZNF198/FGFR1-expressing cells using the GFP antibody (A) identifies the 47-kDa and 32-kDa PAI-2 proteins which are not present in HEK-293 cells expressing GFP alone. The larger 55-kDa band in the IPs is derived from the IgG. (B) The HEK-293 cells expressing GFP (27 kDa) show a nonspecific band at 100 kDa but not the 172-kDa specific band corresponding to the ZNF198/FGFR1 protein (FUS). ZNF198/FGFR1-expressing HEK-293 cells show the fusion protein (172 kDa) and a series of degradation products we described previously.¹⁴  Co-IP with an anti-PAI-2 antibody reveals the 172-kDa ZNF198/FGFR1 protein in cells expressing this fusion kinase gene. Smaller bands in these IPs represent IgG heavy chain band and degradation products.