ERR induces the expression of P c in
ERRγ induces the expression of P450c17 in MA-10 cells and in mouse primary Leydig cells (Fig. 2). Deletion mutant analysis of putative ERRγ-binding sites in the P450c17 promoter suggested that only the proximal third site located between −269 bp and −136 bp within the P450c17 promoter is functional (Fig. 3B). Furthermore, the point mutant of this third site caused the promoter to be unresponsive to ERRγ (Fig. 3C), suggesting it to be the active binding site for ERRγ in the P450c17 promoter. Interestingly, the basal promoter activity between −1040 bp and −132 bp within the P450c17 promoter showed a several-fold difference (Fig. 3B), which could be due to the presence of (+)- Corydaline of other transcription factors, such as AP-1, SF-1 CREB, NFkB, and ATF2/c-JUN, within the 1 kb upstream promoter of the P450c17 gene (data not shown). Previous studies have demonstrated that Nur77 interacts with c-JUN in vitro (Martin and Tremblay, 2009) and that SF-1 directly interacts with c-JUN in a mammalian double-hybrid system (Manna et al., 2004). Both c-Jun and SF-1 can independently and cooperatively activate the StAR promoter (Martin and Tremblay, 2009). The P450c17 upstream promoter (−269 bp to −136 bp) has one putative SF1-binding motif and one putative ATF2/c-JUN-binding motif. If SF1 and c-JUN also interact with each other at the P450c17 promoter as they do at the StAR promoter, it is possible that the basal activity of the −135bp P450c17 upstream promoter will be lower than that of the −269bp P450c17 upstream promoter. Further studies are necessary to elucidate which transcriptional factor affects the basal level of P450c17 promoter activity.
Cross-talk exists between ERRs and members of the NR4A family (Nurr1, Nur77 and Nor1) (Lammi et al., 2007). ERRγ represses Nurr1 transcriptional activity while Nur77 represses ERRγ transcriptional activity. Given that Nur77, as an NR4A family member, shares the DNA-binding site with Nurr1, the above report supports our data that ERRγ inhibits Nur77 transcriptional activity, thereby repressing expression of the StAR and P450c17 genes. Moreover, the repressive mechanism of ERRγ on Nurr1 transactivation excluded competition for DNA binding because the binding of ERRγ to the NBRE was weak. Therefore, further studies are necessary to reveal the mechanism by which ERRγ inhibits Nur77 transactivation.
The present study demonstrated that the protein level of exogenously expressed Nur77 is decreased by coexpression of ERRγ in a dose-dependent manner (Fig. 5). Nur77 protein stability has been previously reported to be regulated through acetylation and deacetylation by p300 and HDAC1 (Kang et al., 2010). p300 induces Nur77 protein stabilization by competing with ubiquitination on the same amino acid residue, while HDAC1 decreases the acetylation level of Nur77, resulting in degradation of Nur77 protein by the ubiquitin-proteasome pathway. Therefore, it is possible that ERRγ is involved in the regulation of deacetylation and ubiquitination of Nur77. Further studies are necessary to elucidate the mechanism of Nur77 destabilization by ERRγ.
Acknowledgement We thank Dr. Mario Ascoli (University of Iowa, Iowa) for kindly providing us the MA-10 mouse Leydig cells. We thank National Research Foundation of Korea (NRF) for the financial support funded by the Ministry of Education, Science and Technology (NRF-2014R1A2A1A11051396).
Introduction Parabens are a homologous series of p-hydroxybenzoic acid esters that differ in the ester group. They have been proven to be very effective antimicrobial agents, and are used extensively, whether singly or in combination, as preservatives in foods, cosmetics, drugs and toiletries. In 1974, the FAO/WHO Joint Expert Committee on Food Additives (JECFA, 1974) allocated an acceptable daily intake of 0–10mg/kg bw (milligrams/kilogram body weight) sum total of methylparaben (MP), ethylparaben (EP) and propylparaben (PP). Over the years, paraben use has steadily increased to include more food categories such as processed vegetables, baked goods, fats and oils, seasonings, sugar substitutes, coffee extracts, fruit juices, pickles, sauces, soft drinks and frozen dairy products at concentrations between 450 and 2000ppm (Daniel, 1986, Soni et al., 2005). Parabens have routinely functioned as preservatives in cosmetics for several decades and are reportedly used in over 13,200 formulations (Elder, 1984). Rastogi et al. (1995) examined the contents of parabens in various cosmetic products and reported a preferential use of MP, EP, PP, butylparaben (BuP) and benzylparaben (BzP). The European Union has allowed the use of parabens and their salts in cosmetic products at a maximum concentration of 0.4% each and a total maximum concentration of 0.8% (EU Cosmetics directive 76/768/EEC), and it has recently recommended a reduction in the sum of PP and BuP to a maximum concentration of 0.19% in the review of SCCS/1348/10.