Fig. 5. ΔF-box β-TrCP1 and ΔF-box β-TrCP2, but not ΔF-box Skp2, inhibit processing of p105. (A) Effect of ΔF-box β-TrCP1 and 2 on the processing of p105. Cos-7 cells were transiently transfected with a cDNA coding for wild-type p105. A cDNA coding for ΔF-box β-TrCP1 (A1) or ΔF-box β-TrCP2 (A2) was co-transfected where indicated. Processing of p105 was monitored in a pulse–chase labeling and immunoprecipitation experiment as described in Materials and methods. (B) Effect of ΔF-box Skp2 on processing of wild-type p105. Cos-7 cells were transiently transfected with a cDNA coding for wild-type p105. cDNAs coding for ΔF-box Skp2 or ΔF-box β-TrCP1 were co-transfected where indicated. Processing of p105 was monitored as described in (A).