C-jun Leucine Zipper Binding Protein (jlip) And Interferon-induced Protein Ifp35 And Its Own Interaction Studies

It was previously revealed in our lab that c-Jun leucine zipper interacting protein (Jlip) could regulate AP-1 (activator protein-1) activity in the caspase-3-dependent manner. Jlip could form a positive feedback loop with caspaes-3 and then sensitize the tumor cells to the apoptotic signals such as TNF (tumor necrosis factor). Here we report that Jlip is also a novel caspae-6 substrate. Jlip was cleaved by caspase-6 at D147, which is C-terminal close to the PH domain. After cleavage, two fragments (PH and APH) were released. Different from plasma membrane-associated full-length Jlip, the cleaved APH fragment was localized to the cytoplasm diffusely. To identify the interacting proteins of APH, we screened the fetal liver cDNA library via yeast two-hybrid. One clone encoding IFP35 (interferon-induced protein 35 kDa) was obtained. The interaction between Jlip-APH and IFP35 was confirmed in the co-immunoprecipitation assay and co-localization study in vivo. These results suggest that Jlip may be involved in the process regulated by interferon. Moreover, we found that Jlip could interact with itself in the yeast two-hybrid system. The self-interaction was also confirmed in the co-immunoprecipitation assay. In addition, we revealed that Jlip could form dimmer and trimer through protein cross-linking method. The leucine zipper in the C-terminus of Jlip may be participated in the dimerization. Our results suggest that homo-dimerization may play a role in the physiological function of Jlip.