title: L7 protein is a coregulator of vitamin D receptor-retinoid X receptor-mediated transactivation.
abstract: The vitamin D receptor (VDR) heterodimerizes with the retinoid X receptor (RXR) and requires additional protein-protein interactions to regulate the expression of target genes. Using the yeast two-hybrid system, we identified the previously described protein L7, that specifically interacted with the VDR in the presence of vitamin D. Deletion analysis indicated, that the N-terminus of L7, which harbours a basic region leucine zipper like domain, mediated interaction with the VDR. Binding assays with purified GST-L7 demonstrated, that L7 specifically pulled down the VDR, that was either expressed in yeast or endogenously contained in the cell line U937. Interestingly, L7 inhibited ligand-dependent VDR-RXR heterodimerization, when constitutively expressed in yeast. We also demonstrate that L7 repressed binding of VDR-RXR heterodimers to a vitamin D response element. Surprisingly, L7 recruited RXR to the same response element in the presence of 9-cis retinoic acid. Ligand-dependent protein-protein interaction in the yeast two-hybrid system confirmed, that binding of L7 also was targeted at the RXR. Our data suggest, that protein L7 is a coregulator of VDR-RXR mediated transactivation of genes, that modulates transcriptional activity by interfering with binding of the receptors to genomic enhancer elements.
authors.affiliation: Hans-Knöll-Institut für Naturstoff-Forschung e.V., Department of Cell and Molecular Biology, Jena, Germany.
authors.forename: Y
authors.initials: Y
authors.lastname: Berghöfer-Hochheimer
authors.forename: C
authors.initials: C
authors.lastname: Zurek
authors.forename: S
authors.initials: S
authors.lastname: Wölfl
authors.forename: P
authors.initials: P
authors.lastname: Hemmerich
authors.forename: T
authors.initials: T
authors.lastname: Munder
mesh_terms: D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D017931:DNA Primers / Q000235:genetics; D019281:Dimerization; D004742:Enhancer Elements, Genetic; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D006801:Humans; D066298:In Vitro Techniques; D008024:Ligands; D011485:Protein Binding; D018167:Receptors, Calcitriol / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018168:Receptors, Retinoic Acid / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D047488:Retinoid X Receptors; D012269:Ribosomal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics; D017384:Sequence Deletion; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014809:Vitamin D-Binding Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D017931:DNA Primers; D029968:Escherichia coli Proteins; D008024:Ligands; C053634:RPL7 protein, human; D018167:Receptors, Calcitriol; D018168:Receptors, Retinoic Acid; D011993:Recombinant Fusion Proteins; D047488:Retinoid X Receptors; D012269:Ribosomal Proteins; D014157:Transcription Factors; D014809:Vitamin D-Binding Protein; C512844:rplL protein, E coli