PIASy inhibits LRH-1-dependent CYP11A1 expression by competing for SRC-1 binding.
The orphan nuclear receptor LRH-1 (liver receptor homologue-1; NR5A2) plays a critical role in development, bile acid synthesis and cholesterol metabolism. LRH-1 is also expressed in the ovary where it is implicated in the regulation of steroidogenic genes for steroid hormone synthesis. In the present study, we investigated the molecular mechanisms of the transcriptional regulation of CYP11A1 by LRH-1 and found that LRH-1-mediated transactivation was markedly repressed by PIASy [protein inhibitor of activated STAT (signal transducer and activator of transcription) y], the shortest member of the PIAS family. The suppression of LRH-1 activity requires the N-terminal repression domain. Although PIAS proteins also function as E3 SUMO (small ubiquitin-related modifier) ligases and enhance SUMO conjugation, PIASy-mediated repression was independent of LRH-1 SUMOylation status. In addition, histone deacetylase activity was not involved in the inhibition of LRH-1 by PIASy. Immunoprecipitation and mammalian two-hybrid analyses indicated that PIASy interacted with LRH-1 through the C-terminal region, including the AF-2 (activation function-2) motif, which was also involved in the interaction between LRH-1 and the co-activator SRC-1 (steroid receptor co-activator-1). PIASy inhibited the binding of SRC-1 to LRH-1, although overexpression of SRC-1 partially overcame the PIASy inhibition of LRH-1 induction of the CYP11A1 promoter. The results of the present study suggest that competition with co-activators may be an important mechanism underlying the PIASy repression of LRH-1-mediated transactivation.
Hsieh
Hsiang-Tsan
HT
Graduate Institute of Physiology, National Taiwan University College of Medicine, Taipei 100, Taiwan.
Wang
Chih-Hung
CH
Wu
Mei-Ling
ML
Yang
Feng-Ming
FM
Tai
Yu-Chen
YC
Hu
Meng-Chun
MC
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000494:pharmacology*; D051548:Histone Acetyltransferases / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D051379:Mice; D056920:Nuclear Receptor Coactivator 1; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D050828:Protein Inhibitors of Activated STAT / Q000378:metabolism / Q000494:pharmacology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism* / Q000494:pharmacology*; D014162:Transfection; D020798:Two-Hybrid System Techniques
D004268:DNA-Binding Proteins; C082631:NR5A2 protein, human; D050828:Protein Inhibitors of Activated STAT; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; D002786:Cholesterol Side-Chain Cleavage Enzyme; D051548:Histone Acetyltransferases; C538859:NCOA1 protein, human; C538861:Ncoa1 protein, mouse; D056920:Nuclear Receptor Coactivator 1