Repression of the promoter activity mediated by liver receptor homolog-1 through interaction with ku proteins

Biol Pharm Bull. 2010;33(5):784-91. doi: 10.1248/bpb.33.784.

Abstract

Nuclear receptor liver receptor homolog-1 (LRH-1; NR5A2) plays a crucial role in the homeostasis of bile acids and cholesterol by controlling the expression of genes central to bile acid synthesis and efflux, reverse cholesterol transport, and high density lipoprotein-remodeling. However, the molecular mechanisms that modulate the transactivation activity of LRH-1 remain unclear. It is proposed that LRH-1's activity is regulated by post-modifications, the binding of small heterodimer partner (SHP), or the binding of coregulators. To search for cofactors that regulate the transactivation activity of LRH-1, we performed a pull-down assay using glutathione S-transferase (GST) fused to the N-terminal portion of LRH-1 and nuclear extracts from HeLa cells, and identified Ku proteins as interacting proteins with LRH-1. We also found that Ku proteins associate with LRH-1 through its DNA-binding domain and hinge region. Luciferase reporter assays revealed that Ku proteins repressed the SHP promoter activity mediated by LRH-1. Furthermore, Ku proteins suppressed the coactivating effect of peroxisome proliferator-activated receptor (PPAR) gamma coactivator-1alpha (PGC-1alpha), an LRH-1 coactivator, on the LRH-1-mediated SHP promoter activity. Previously, we showed that Ku proteins interacted with nuclear receptor farnesoid X receptor (FXR; NR1H4) and decreased the expression of its target gene. In this study, we demonstrated that Ku proteins also interacted with not only LRH-1 but various nuclear receptors, such as the estrogen receptor, PPAR, and Rev-erb. Ku proteins may function as corepressors for various nuclear receptors including LRH-1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • Co-Repressor Proteins / metabolism*
  • DNA
  • DNA Helicases / genetics
  • DNA Helicases / metabolism*
  • Dimerization
  • Gene Expression Regulation*
  • Gene Expression*
  • Glutathione Transferase
  • HeLa Cells
  • Heat-Shock Proteins / genetics
  • Heat-Shock Proteins / metabolism
  • Humans
  • Ku Autoantigen
  • Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha
  • Promoter Regions, Genetic*
  • Receptors, Cytoplasmic and Nuclear / metabolism*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Transcriptional Activation

Substances

  • Co-Repressor Proteins
  • Heat-Shock Proteins
  • PPARGC1A protein, human
  • Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha
  • Receptors, Cytoplasmic and Nuclear
  • Transcription Factors
  • DNA
  • Glutathione Transferase
  • DNA Helicases
  • XRCC5 protein, human
  • Ku Autoantigen