L7 protein is a coregulator of vitamin D receptor-retinoid X receptor-mediated transactivation

J Cell Biochem. 1998 Apr 1;69(1):1-12. doi: 10.1002/(sici)1097-4644(19980401)69:1<1::aid-jcb1>3.0.co;2-x.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Binding Sites / genetics
  • Cell Line
  • DNA Primers / genetics
  • Dimerization
  • Enhancer Elements, Genetic
  • Escherichia coli / genetics
  • Escherichia coli Proteins
  • Humans
  • In Vitro Techniques
  • Ligands
  • Protein Binding
  • Receptors, Calcitriol / chemistry
  • Receptors, Calcitriol / genetics
  • Receptors, Calcitriol / metabolism*
  • Receptors, Retinoic Acid / chemistry
  • Receptors, Retinoic Acid / genetics
  • Receptors, Retinoic Acid / metabolism*
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Retinoid X Receptors
  • Ribosomal Proteins / chemistry
  • Ribosomal Proteins / genetics
  • Ribosomal Proteins / metabolism*
  • Saccharomyces cerevisiae / genetics
  • Sequence Deletion
  • Transcription Factors / chemistry
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*
  • Transcriptional Activation*
  • Vitamin D-Binding Protein / chemistry
  • Vitamin D-Binding Protein / genetics
  • Vitamin D-Binding Protein / metabolism


  • DNA Primers
  • Escherichia coli Proteins
  • Ligands
  • RPL7 protein, human
  • Receptors, Calcitriol
  • Receptors, Retinoic Acid
  • Recombinant Fusion Proteins
  • Retinoid X Receptors
  • Ribosomal Proteins
  • Transcription Factors
  • Vitamin D-Binding Protein
  • rplL protein, E coli