PHB2 interacts with RNF2 and represses CP2c-stimulated transcription.

RNF2, a polycomb group protein, is an important component of PRC complex regulating transcriptional activity. Recently, several RNF2 interacting proteins have been identified. Thus, RNF2 might have multiple activities, depending on its interacting partner proteins. In the present study, using the yeast two-hybrid system, we have found that RNF2 interacts with the PHB2 protein. Luciferase reporter assays showed that RNF2 represses the CP2c-stimulated luciferase activity in a PHB2 dose-dependent manner. Further experiments with RNF2 deletion mutants indicated that RNF21–158 is sufficient for both the physical association and functional co-operation with the PHB2 protein. Co-immunoprecipitation experiments revealed that PHB2 and CP2c bind to the N- and C-terminals of RNF2, respectively. Luciferase reporter assays using α-globin promoter with CP2-binding elements hinted that RNF2 and PHB2 are involved in the CP2-stimulated expression of the α-globin gene. Our study suggests a novel mechanism by which RNF2 and PHB2 modulate the CP2-mediated transcriptional pathway.