Characterization of the interaction between Mitogen-activated protein kinase: JNK1 and its scaffold protein JIP1

JUAN ANGIOLINI, ADRIAN TURJANSKI, VALERIA LEVI, DIANA WETZLER.

Congreso; eunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2010

The JNK MAPKs are characterized by the dual phosphorylation motif T-P-Y within their activation loop. JNK was discovered by its ability to phosphorylate the N-terminal transactivating domain of the transcription factor c-Jun.  Scaffold proteins, which bind signaling molecules thereby creating functional modules that ensure the specificity of signal transmission, can increase the efficiency of the MAPK activation process. JNK binds their upstream regulators (MAPKKs), downstream targets and scaffold protein by surface interactions that are achieved through docking motif binding sites that are outside of the catalytic domain. However, it is not clear how the signaling modules can be formed when all MAPK protein-protein interactions are in the same binding region. This raise the following questions, are scaffolds, MAPKKs and targets competing for the same binding region? Does JNK phosphorylation regulate binding affinities?  The general objective is to study in vitro binding selectivity of JNK1 towards MKK7, JIP1 and c-jun. We present here a detail study of JNK1-JIP1 interaction by classical spectroscopic techniques (circular dichroism, fluorescence anisotropy) and advanced techniques like fluorescence correlation spectroscopy. This work serves as a starting point to understand the paradox that scaffold protein, upstream regulator and transcription factor bind JNK in a competitive way.