Characterization of a novel JNK2-interacting protein, C331.

Abstract

c-Jun N-terminal kinases (JNK) interact with a variety of proteins to evoke diverse cellular responses. A novel JNK2-interacting protein, C331, has been identified in the laboratory by yeast two-hybrid screening. Besides yeast, it was found that this interaction occurs in mammalian cells, however, only in presence of genotoxic stress. In this project, my work was directed towards identification of site(s) in C331 involved in interaction with JNK. Amino-acid sequence analysis of C331 revealed the presence of a JNK-docking domain – D-domain – a consensus sequence similar to those found in other known JNK-interacting proteins. Using site-directed mutagenesis, the D-domain was disrupted in C331 by sequential replacement of basic residues with alanine. Binding studies with this mutant dC331 revealed that loss of basic residues in the putative D-domain is insufficient to abolish C331 association with JNK2; instead, it enhanced the association with JNK. However, luciferase reporter assays showed that potentiation of p53-dependent transcription – another function associated to C331 – was defective in dC331, suggesting that the D-domain contributed to this function. Two deletion mutants of C331 were also generated, which will be used in future studies to provide insights into the phenomenon of JNK – C331 interaction.