PIASy inhibits LRH-1-dependent CYP11A1 expression by competing for SRC-1 binding

Abstract

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.

Molecular basis for the regulation of the nuclear receptor LRH-1

“…While SRC-1 stimulates, PIASy transrepresses LRH-1-dependent Cyp11a1 promoter activation. Although PIASy is an E3 SUMO-ligase, its transrepressive function does not seem to result from changes in the LRH-1 SUMOylation status [59]. In another study that investigated the transcriptional regulation of the Lrh-1 gene upon sphingosine-1-phosphate and prostaglandin E2 stimulation, it was shown that CCAAT/enhancer binding proteins d (C/EBPd) and the coactivators CREB-binding protein (CBP) and SRC-3 potentiate the interaction of cAMP response element binding protein (CREB) and LRH-1 [60].…”

“…For example, stimulation of rat primary granulosa cells with pregnant mare serum gonadotropin (PMSG) leads to the SRC-1/LRH-1 transactivation of the inhibin alphasubunit gene, a gene that inhibits the release of folliclestimulating hormone (FSH) [10]. In the transcriptional regulation of the Cyp11a1 gene, SRC-1 and protein inhibitor of activated STAT (signal transducer and activator of transcription) y (PIASy) compete to bind LRH-1 [59]. While SRC-1 stimulates, PIASy transrepresses LRH-1-dependent Cyp11a1 promoter activation.…”

Molecular characterization, expression, polymorphism of NR5A2 and its relationship with litter size in Hu sheep

“…NR5A2 is involved in a variety of processes including ovulation and embryo differentiation and development (Fayard et al, 2004;Hsieh et al, 2009;Yazawa et al, 2010;Winkler et al, 2010). Hinshelwood et al (2005) found that NR5A2 plays a role in gonadal development, the initiation of folliculo genesis, and regulation of estrogen biosynthesis within the ovary.…”

“…Kisspeptin neuron-specific NR5A2 knockout mice (NR5A2 kiss-1-/-) have significantly reduced litter sizes (Atkin et al, 2013). In the ovary, NR5A2 regulates genes involved in follicular development, such as CYP11A1 (Hsieh et al, 2009); STAR (Taniguchi et al, 2009); HSD3B2 (Peng et al, 2003); INHA (Matulis and Mayo, 2012); and FDX1 (Imamichi et al, 2013). NR5A2 is expressed in the anterior pituitary, and regulates key genes underlying follicular development such as those encoding GnRHR (gonadotropin-releasing hormone receptor), LHR (luteinizing hormone receptor), and FSHR (follicle stimulating hormone receptor) (Zheng et al, 2007).…”

Identification of two functional nuclear localization signals mediating nuclear import of liver receptor homologue-1

“…Western blot analyses were performed as previously described [33]. The anti-Myc antibody was used to assess the expression of Myc-LRH-1, while anti-b-actin antibody determination of b-actin levels (Upstate Biotechnology) was used as a loading control.…”