title: Repression of the promoter activity mediated by liver receptor homolog-1 through interaction with ku proteins.
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.
authors.affiliation: Department of Molecular Biology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabedori, Mizuho-ku, Nagoya, Aichi 467-8603, Japan.
authors.forename: Masae
authors.initials: M
authors.lastname: Ohno
authors.forename: Jun
authors.initials: J
authors.lastname: Komakine
authors.forename: Eiko
authors.initials: E
authors.lastname: Suzuki
authors.forename: Makoto
authors.initials: M
authors.lastname: Nishizuka
authors.forename: Shigehiro
authors.initials: S
authors.lastname: Osada
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Imagawa
mesh_terms: D002460:Cell Line; D056970:Co-Repressor Proteins / Q000378:metabolism*; D004247:DNA; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D015870:Gene Expression; D005786:Gene Expression Regulation; D005982:Glutathione Transferase; D006367:HeLa Cells; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D000072200:Ku Autoantigen; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D011401:Promoter Regions, Genetic; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation
chemical_list: D056970:Co-Repressor Proteins; D006360:Heat-Shock Proteins; C486497:PPARGC1A protein, human; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; D004247:DNA; D005982:Glutathione Transferase; D004265:DNA Helicases; C106893:XRCC5 protein, human; D000072200:Ku Autoantigen