Figure 6.

UV promotes dimerization of Ret-MEN2A and Ret-MEN2B. Lysates from NIH 3T3 cells transfected with RET-MEN2A (A–E) or RET-MEN2B (F–I) after sham or UV irradiation were subjected to either Western blotting with anti-Ret antibody (A, B, F, and G) or in vitro kinase assay (C, D, E, H, and I) after immunoprecipitation with anti-Ret antibody. SDS-PAGE was done under reducing (A, C, E, F, and H) or unreducing (B, D, G, and I) conditions in 5% polyacrylamide gels. (E) The dimerized bands in D were cut from the gel and separated under reducing conditions. Lanes 1, sham irradiation; lanes 2, 5 min after UV-B irradiation (600 J/m²). M, monomer Ret; D, dimer Ret. For direct comparison of kinase activity between Ret-MEN2A and Ret-MEN2B, see Figure 2. All measurements were repeated three times with basically the same results. Representative results are provided.