supporting the notion of activated JNK1 and JNK2 in the suppression of b-catenin signaling. Active JNK2 Directly Interacts with GSK3b and b-catenin Although our data strongly demonstrate that JNK2 suppresses b-catenin signaling through GSK3b-proteasome pathway, the mechanism underlying the regulation of GSK3b activity by active JNK2 remains elusive. In addition, we can not exclude the possibility that JNK2 can directly interact with b-catenin. Therefore, immunoprecipitation assays were carried out to test a potential interaction between JNK2, GSK3b, and/or b-catenin. As shown in figure 5A, both b-catenin and GSK3b can be seen in the precipitate by anti-Flag tag antibody (lane 2), but they were absent in the cells without Flag-tagged constitutively active JNK2 (lane 1), indicating that active JNK2 indeed interacted with GSK3b and b-catenin. It is possible that JNK2, GSK3b and b- catenin form a multi-protein complex since cytoplasmic interac- tion of GSK3b and b-catenin has been found [26,27]. The interaction between JNK2 and b-catenin was further validated by mammalian two-hybridization system (Figure 5B) and co-locali- zation analysis (Figure 5C), as we reported recently [2]. As shown in figure 5C, active JNK2 was co-localized with b-catenin in the nucleus and cytoplasm, consistent with the results from the immunoprecipitation assays. Since overexpressed b-catenin is mainly restricted in the nucleus as shown in figure 5C and reported previously [2,4], it is postulated that activated JNK2 promotes b-catenin degradation by increasing GSK3b and proteasome activity and potentially degrading b-catenin in the cytoplasm by driving b-catenin translocation. In fact, JNK1 was also reported to antagonize References 1. Clevers H (2006) Wnt/[b]-Catenin Signaling in Development and Disease. Cell 127: 469–480. 2. 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