|Ph.D Student||Katz Sigal|
|Subject||Identifying the Mechanism of JNK(c-Jun N-terminal kinase)|
Substrate-Specificity and Selectivity
|Department||Department of Medicine||Supervisor||Professor Ami Aronheim|
The mitogen-activated kinases (MAPKs) amplify and integrate signals from a variety of stimuli to produce specific cell responses. These structurally related proline-directed serine/threonine kinases phosphorylate similar phosphoacceptor sites yet, they exhibit stringent substrate specificity. One mechanism by which MAPKs maintain specificity is by physically associating with their substrates via docking sites. Recently, we have identified c-Jun dimerization protein 2 (JDP2) as a bona fide substrate for JNK and p38. JDP2 is a basic leucine zipper protein member of the AP-1 family, isolated based on its ability to interact with c-Jun bZIP domain. Our aim was to identify a JNK docking domain within JDP2 that will enable identification of novel putative substrates and other JNK-interacting proteins.
Activating transcription factor 3 (ATF3) is a basic leucine zipper protein highly homologous to JDP2, especially within the phosphoacceptor site. ATF3 does not serve as a JNK substrate in vitro or in vivo. Using ATF3 and JDP2 protein chimeras, deletion analysis and mutagenesis screen, we mapped a novel JNK-docking domain within JDP2 located C-terminally to the phosphoacceptor site. This novel domain is necessary but not sufficient for p38 phosphorylation of JDP2 on Thr-148.
In addition, using the Ras recruitment yeast two-hybrid system (RRS) our group in collaboration with Dr. Kallunki cloned a novel JNK-interacting protein designated IB kinase complex-associated protein (IKAP) and demonstrated a novel role for the regulation of activation of the mammalian stress response via the JNK-signaling pathway. This study may promote the identification of additional JNK substrates thereby enabling a better understanding of JNK biological functions.