ERC-55, A BINDING-PROTEIN FOR THE PAPILLOMA-VIRUS E6 ONCOPROTEIN, SPECIFICALLY INTERACTS WITH VITAMIN-D-RECEPTOR AMONG NUCLEAR RECEPTORS

VDR regulates gene expression in a ligand-dependent way by binding to cognate enhancer elements of target gene promoters. The ligand-depende nt activation function, AF-2, of VDR is thought to require transcripti onal co-activators/co-repressors together with basal transcriptional m achinery. Using a yeast two hybrid system with VDR, we have isolated a mouse Ca2+-binding protein(designated as VAF1) specifically interacti ng in vivo and in vitro with VDR among nuclear receptors like RAR, RXR , ER and GR. VAF1 is a mouse homologue to human ERC-55, which has rece ntly been shown to interact with human papillomavirus oncogenic protei n, E6[1]. Unlike those of many previously identified co-activators, th e VDR-VAF1 interaction was ligand-independent. Thus, VAF1 seems a puta tive VDR-specific cofactor modulating its function. (C) 1997 Academic Press.