Figure 5.

Pin1 induces JNK1 activity by enhancing the interaction between JNK1 and its substrates. (a) Pin1^−/− MEFs were transfected with expression plasmids for FLAG-JNK1 alone or both JNK1 and Pin1 WT or various point mutants of Pin1. Cell extracts were immunoprecipitated with FLAG M2 agarose beads. The beads were washed twice with the lysis buffer and then incubated with 1 μg of GST-c-Jun. Protein complexes bound to the beads were subjected to SDS-PAGE, and then immunoblotted with an anti-GST antibody. The binding affinity relative to the amount of JNK1 is shown as the fold increase. (b) Lysates from H₂O₂-treated or -untreated Pin1^−/− and Pin1^+/+ MEFs were analyzed by immunoprecipitation and then immunoblotting as described in Materials and Methods