Oncogenic nucleoporin CAN/Nup214 interacts with vitamin D receptor and modulates its function

Vitamin D receptor (VDR) is a ligand-dependent transcription factor and should be located in nucleus to transactivate target genes. To explore the molecules that interact with VDR and facilitate its nuclear localization, we screened a human kidney cDNA library using the yeast two-hybrid approach, and found that VDR binds to the carboxy-terminal region of an oncogenic nucleoporin, CAN/Nup214. CAN/Nup214 was originally identified through its involvement in a certain type of acute myeloid leukemia, and is a component of nuclear pore complex (NPC). Co-immunoprecipitation experiments confirmed the interaction between VDR and the carboxy-terminus of CAN/Nup214 containing a cluster of the phenylalanine-glycine (FG) repeat in mammalian cells. The exogenously expressed full-length CAN/Nup214 was localized predominantly at the nuclear envelope, suggesting its integration in the NPCs. We then examined the effects of exogenous expression of full-length CAN/Nup214 and its carboxy-terminal fragment on the VDR-mediated transactivation. The overexpression of full-length CAN/Nup214 facilitated the VDR-mediated transactivation, while the expression of the carboxy-terminal fragment suppressed it. The DNA-binding domain of VDR was required for the facilitation of the VDR-dependent transactivation by CAN/Nup214. Although the subcellular distribution of VDR was not obviously altered by the overexpression of full-length CAN/Nup214 or the carboxy-terminal fragment, the expression of the carboxy-terminal fragment inhibited the interaction between full-length CAN/Nup214 and VDR. These results indicate that CAN/Nup214 interacts with VDR and modulates its function as a transcription factor.