Regulation of the human P450scc gene by steroidogenic factor 1 is mediated by CBP/p300

Steroidogenic Factor-1 form and function: From phospholipids to physiology

Steroidogenic Factor-1 (SF-1, NR5A1) is a member of the nuclear receptor superfamily of ligand-regulated transcription factors, consisting of a DNA-binding domain (DBD) connected to a transcriptional regulatory ligand binding domain (LBD) via an unstructured hinge domain. SF-1 is a master regulator of development and adult function along the hypothalamic pituitary adrenal and gonadal axes, with strong pathophysiological association with endometriosis and adrenocortical carcinoma. SF-1 was shown to bind and be regulated by phospholipids, one of the most interesting aspects of SF-1 regulation is the manner in which SF-1 interacts with phospholipids: SF-1 buries the phospholipid acyl chains deep in the hydrophobic core of the SF-1 protein, while the lipid headgroups remain solvent-exposed on the exterior of the SF-1 protein surface. Here, we have reviewed several aspects of SF-1 structure, function and physiology, touching on other transcription factors that help regulate SF-1 target genes, non-canonical functions of SF-1, the DNA-binding properties of SF-1, the use of mass spectrometry to identify lipids that associate with SF-1, how protein phosphorylation regulates SF-1 and the structural biology of the phospholipid-ligand binding domain. Together this review summarizes the form and function of Steroidogenic Factor-1 in physiology and in human disease, with particular emphasis on adrenal cancer.

FDX1 regulates leydig cell ferroptosis mediates PM2.5-induced testicular dysfunction of mice

Epidemiological studies have established an association between chronic exposure to PM2.5 and male infertility. However, the underlying mechanisms were not fully revealed. In this study, we established mice models exposed to PM2.5 for 16 weeks, and a significant decrease in sperm quality accompanied by an increase in testosterone levels were observed after PM2.5 exposure. Moreover, treatment with ferrostatin-1 (Fer-1), a specific ferroptosis inhibitor, effectively mitigated PM2.5-induced testicular dysfunction in mice. And lipid peroxidation and ferritin accumulation were found to be significantly increased in Leydig cells of testes with a PM2.5-dose dependent manner. Further investigations revealed that TM-3 cells, a mouse Leydig cell line, were prone to ferroptosis after PM2.5 exposure, and the cell viability was partly rescued after the intervention of Fer-1. Furthermore, our results supported that the ferroptosis of TM-3 cells was attributed to the upregulation of ferredoxin 1 (FDX1), which was the protein transferring electrons to cytochrome P450 family 11 subfamily A member 1 to aid lysing cholesterol to pregnenolone at initial of steroidogenesis. Mechanically, PM2.5-induced FDX1 upregulation resulted in cellular ROS elevation and ferrous iron overload, which together initiated an autoxidation process of polyunsaturated fatty acids in the cell membrane of Leydig cells until the accumulated lipid peroxides triggered ferroptotic cell death. Simultaneously, upregulation of FDX1 promoted steroidogenesis and let to an increased level of testosterone. In summary, our work suggested that FDX1, a mediator involving steroidogenesis, was a key regulator in PM2.5-induced Leydig cells ferroptosis.

Novel heterozygous variants in the EP300 gene cause Rubinstein-Taybi syndrome 2: Reports from two Chinese children

BACKGROUND

Rubinstein-Taybi syndrome (RSTS) is a rare autosomal-dominant genetic disease caused by variants of CREBBP (RSTS1) or EP300 (RSTS2) gene. RSTS2 is much less common, with less than 200 reported cases worldwide to date. More reports are still needed to increase the understanding of its clinical manifestations and genetic characteristics.

METHODS

The clinical data of two children with RSTS2 were analyzed retrospectively, and their clinical manifestations, auxiliary examinations, and mutational spectrum were summarized. Liquid chromatography-tandem mass spectrometer (LC-MS/MS) technology was used to detect the levels of steroid hormones if possible.

RESULTS

After analyzing the clinical and genetic characteristics of two boys with RSTS2 (0.7 and 10.4 years old, respectively) admitted in our hospital, we identified two novel heterozygous variants in the EP300 exon 22 (c.3750C > A, p. Cys1250*, pathogenic; c.1889A > G, p. Tyr630Cys, likely pathogenic), which could account for their phenotype. In addition to common clinical manifestations such as special facial features, microcephaly, growth retardation, intellectual disability, speech delay, congenital heart defect, recurrent respiratory infections, and immunodeficiency, we found one of them had a rare feature of adrenal insufficiency, and LC-MS/MS detection showed an overall decrease in steroid hormones.

CONCLUSION

In our study, we identified two novel variants in the EP300 exon 22, and for the first time, we reported a case of RSTS2 associated with adrenal insufficiency, which will enrich the clinical and mutational spectrum of this syndrome.

Prohibitin-1 plays a regulatory role in Leydig cell steroidogenesis

Mitochondria are essential for steroidogenesis. In steroidogenic cells, the initiation of steroidogenesis from cholesterol occurs on the matrix side of the inner mitochondrial membrane by the enzyme P450scc. This requires cholesterol import from the cytoplasm through the outer mitochondrial membrane, facilitated by the StAR protein. The subsequent steps leading to P450scc remain elusive. Here we report that the male transgenic mice that expressed a mutant form of a mitochondrial protein prohibitin-1 (PHB1^Tyr114Phe) from the Fabp-4 gene promoter displayed smaller testes, higher testosterone, and lower gonadotropin levels compared with PHB1-expressing and wild-type mice. A subsequent analysis of the testis and Leydig cells from the mice revealed that PHB1 played a previously unknown regulatory role in Leydig cell steroidogenesis. This includes a role in coordinating cell signaling, cholesterol homeostasis, and mitochondrial biology pertaining to steroidogenesis. The implications of our finding are broad as the initial stages of steroidogenesis are indistinguishable across steroidogenic cells.

•

Tyr114Phe-PHB-1 transgenic male mice reveal PHB-1’s role in testosterone production

•

PHB-1 coordinates steroidogenic signaling and events in testosterone biosynthesis

•

Tyr114 residue in PHB-1 plays a regulatory role in testosterone production

Intergenerational genetic programming mechanism and sex differences of the adrenal corticosterone synthesis dysfunction in offspring induced by prenatal ethanol exposure

We previously found that prenatal ethanol exposure (PEE) induced adrenal dysplasia in offspring, which was related to intrauterine maternal glucocorticoid overexposure. This study investigated the intergenerational genetic effect and sex differences of PEE-induced changes in the synthetic function of adrenal corticosterone in offspring, and to clarify the intrauterine origin programming mechanism. Wistar pregnant rats were gavaged with ethanol (4 g/kg bw/d) from gestation day (GD) 9-20, and F1 generation was born naturally. The F1 generation female rats in the PEE group were mated with normal male rats to produce F2 generation. Serum and adrenal glands of fetal rats and F1/F2 adult rats were collected at GD20 and postnatal week 28. PEE increased the serum corticosterone level, while diminishing the expression of adrenal steroid synthases of fetal rats. Moreover, PEE enhanced the mRNA expression of GR and HDAC1, but inhibited the mRNA expression of SF1 and reduced the H3K9ac level of P450scc in the fetal adrenal gland. In PEE adult offspring of F1 and F2 generation the serum corticosterone level, the H3K9ac level of P450scc and its expression were decreased in males but were increased in females. In NCI-H295R cells, cortisol reduced the production of endogenous cortisol, down-regulated SF1, and up-regulated HDAC1 expression by activating GR, and decreased H3K9ac level and expression of P450scc. In conclusion, PEE could induce adrenal dysplasia in offspring with sex differences and intergenerational genetic effects, and the adrenal insufficiency in male offspring was related to the induction of low functional genetic programming of P450scc by intrauterine high corticosterone through the GR/SF1/HDAC1 pathway.

Novel NR5A1 mutations found in Chinese patients with 46, XY disorders of sex development

OBJECTIVE

To analyze nuclear receptor subfamily 5 group A member 1 (NR5A1) gene mutations in a cohort of Chinese patients with 46, XY Disorders of Sex Development (DSD).

METHODS

Sixty 46, XY DSD patients were recruited at Peking Union Medical College Hospital. Targeted next-generation and Sanger sequencing were performed to investigate pathogenic gene variants and validate NR5A1 gene variants, respectively. In silico tools and in vitro function studies were used to analyze the pathogenicity of rare variants. The clinical and endocrinological characteristics of patients with NR5A1 variants were retrospectively analyzed.

RESULTS

A total of four novel and three recurrent NR5A1 variants were identified in seven 46, XY DSD patients. These variants widely spread almost all the functional domains. Functional studies showed that novel mutations including p.S32N, p.N44del and p.G91D reduced transactivation of CYP11A1, while the other missense variant p.A168E did not impact protein function. All patients with NR5A1 rare variants had normal adrenal function and showed genital defects. Results of the genitalia examination showed female external genitalia (three patients), ambiguous external genitalia (two patients), female external genitalia with clitoromegaly (one patient), and hypospadias (one patient). All seven patients had bilateral testis and five of seven patients lacked Müllerian structures.

CONCLUSIONS

Four novel mutations in the NR5A1 gene were identified in our cohort with 46, XY DSD, expanding the spectrum of NR5A1 gene mutations. All patients with NR5A1 rare variants had normal adrenal function and showed genital defects.

Study on the transcriptional regulatory mechanism of the MyoD1 gene in Guanling bovine

The MyoD1 gene plays a key role in regulating the myoblast differentiation process in the early stage of skeletal muscle development. To understand the functional elements of the promoter region and transcriptional regulation of the bovine MyoD1 gene, we cloned eight fragments from the sequence region of the MyoD1 gene promoter and inserted them into eukaryotic expression vectors for cotransfection with the mouse myoblast cell line C2C12 and Madin-Darby bovine kidney (MDBK) line. A variety of transcription factor binding sites in the longest 5'-flanking fragment from Guanling cattle MyoD1-P1 were predicted by using the online software TFSEARCH and ALGGEN PROMO as well as validated by the promoter-binding TF profiling assay II and yeast one-hybrid (Y1H) assay, including MyoD, VDR, MEF1, MEF2, SF1, and Myf6. Myf6 strongly activated the MyoD1 promoter, while MyoD1 was also capable of efficiently activating the expression of its own promoter. The transcription factors MEF2A, SF1, and VDR were further confirmed to be capable of binding to MyoD1 by Y1H system experiments. The effects of the Guanling cattle MyoD1 gene on the mRNA expression of the MEF2A, SF1, and VDR genes were determined by using a lentivirus-mediated overexpression technique, confirming that overexpression of the MyoD1 gene upregulated the mRNA expression of MEF2A as well as downregulated the expression of SF1 and VDR in the process of muscle myogenesis. Our study revealed the effects of transcription factors including MEF2A, SF1 and VDR on regulatory aspects of MyoD1, providing abundant information for transcriptional regulation of MyoD1 in muscle differentiation.

Multiple functions of CREB-binding protein during postembryonic development: identification of target genes

Background

Juvenile hormones (JH) and ecdysteroids control postembryonic development in insects. They serve as valuable targets for pest management. Hence, understanding the molecular mechanisms of their action is of crucial importance. CREB-binding protein (CBP) is a universal transcriptional co-regulator. It controls the expression of several genes including those from hormone signaling pathways through co-activation of many transcription factors. However, the role of CBP during postembryonic development in insects is not well understood. Therefore, we have studied the role of CBP in postembryonic development in Tribolium, a model coleopteran insect.

Results

CBP is ubiquitously expressed in the red flour beetle, Tribolium castaneum. RNA interference (RNAi) mediated knockdown of CBP resulted in a decrease in JH induction of Kr-h1 gene expression in Tribolium larvae and led to a block in their development. Moreover, the injection of CBP double-stranded RNA (dsRNA) showed lethal phenotypes within 8 days of injection. RNA-seq and subsequent differential gene expression analysis identified CBP target genes in Tribolium. Knockdown of CBP caused a decrease in the expression of 1306 genes coding for transcription factors and other proteins associated with growth and development. Depletion of CBP impaired the expression of several JH response genes (e.g., Kr-h1, Hairy, early trypsin) and ecdysone response genes (EcR, E74, E75, and broad complex). Further, GO enrichment analyses of the downregulated genes showed enrichment in different functions including developmental processes, pigmentation, anatomical structure development, regulation of biological and cellular processes, etc.

Conclusion

These data suggest diverse but crucial roles for CBP during postembryonic development in the coleopteran model insect, Tribolium. It can serve as a target for RNAi mediated pest management of this stored product pest.

Electronic supplementary material

The online version of this article (10.1186/s12864-017-4373-3) contains supplementary material, which is available to authorized users.

Role of Nuclear Receptors in Central Nervous System Development and Associated Diseases

The nuclear hormone receptor (NHR) superfamily is composed of a wide range of receptors involved in a myriad of important biological processes, including development, growth, metabolism, and maintenance. Regulation of such wide variety of functions requires a complex system of gene regulation that includes interaction with transcription factors, chromatin-modifying complex, and the proper recognition of ligands. NHRs are able to coordinate the expression of genes in numerous pathways simultaneously. This review focuses on the role of nuclear receptors in the central nervous system and, in particular, their role in regulating the proper development and function of the brain and the eye. In addition, the review highlights the impact of mutations in NHRs on a spectrum of human diseases from autism to retinal degeneration.

Impact of ACTH Signaling on Transcriptional Regulation of Steroidogenic Genes

The trophic peptide hormone adrenocorticotropic (ACTH) stimulates steroid hormone biosynthesis evoking both a rapid, acute response and a long-term, chronic response, via the activation of cAMP/protein kinase A (PKA) signaling. The acute response is initiated by the mobilization of cholesterol from lipid stores and its delivery to the inner mitochondrial membrane, a process that is mediated by the steroidogenic acute regulatory protein. The chronic response results in the increased coordinated transcription of genes encoding steroidogenic enzymes. ACTH binding to its cognate receptor, melanocortin 2 receptor (MC2R), stimulates adenylyl cyclase, thus inducing cAMP production, PKA activation, and phosphorylation of specific nuclear factors, which bind to target promoters and facilitate coactivator protein recruitment to direct steroidogenic gene transcription. This review provides a general view of the transcriptional control exerted by the ACTH/cAMP system on the expression of genes encoding for steroidogenic enzymes in the adrenal cortex. Special emphasis will be given to the transcription factors required to mediate ACTH-dependent transcription of steroidogenic genes.

Adrenal Mitochondria and Steroidogenesis: From Individual Proteins to Functional Protein Assemblies

The adrenal cortex is critical for physiological function as the central site of glucocorticoid and mineralocorticoid synthesis. It possesses a great degree of specialized compartmentalization at multiple hierarchical levels, ranging from the tissue down to the molecular levels. In this paper, we discuss this functionalization, beginning with the tissue zonation of the adrenal cortex and how this impacts steroidogenic output. We then discuss the cellular biology of steroidogenesis, placing special emphasis on the mitochondria. Mitochondria are classically known as the "powerhouses of the cell" for their central role in respiratory adenosine triphosphate synthesis, and attention is given to mitochondrial electron transport, in both the context of mitochondrial respiration and mitochondrial steroid metabolism. Building on work demonstrating functional assembly of large protein complexes in respiration, we further review research demonstrating a role for multimeric protein complexes in mitochondrial cholesterol transport, steroidogenesis, and mitochondria-endoplasmic reticulum contact. We aim to highlight with this review the shift in steroidogenic cell biology from a focus on the actions of individual proteins in isolation to the actions of protein assemblies working together to execute cellular functions.

CREB-binding protein contributes to the regulation of endocrine and developmental pathways in insect hemimetabolan pre-metamorphosis

BACKGROUND

CREB-binding protein (CBP) is a promiscuous transcriptional co-regulator. In insects, CBP has been studied in the fly Drosophila melanogaster, where it is known as Nejire. Studies in D. melanogaster have revealed that Nejire is involved in the regulation of many pathways during embryo development, especially in anterior/posterior polarity, through Hedgehog and Wingless signaling, and in dorsal/ventral patterning, through TGF-ß signaling. Regarding post-embryonic development, Nejire influences histone acetyl transferase activity on the ecdysone signaling pathway.

METHODS AND RESULTS

Functional genomics studies using RNAi have shown that CBP contributes to the regulation of feeding and ecdysis during the pre-metamorphic nymphal instar of the cockroach Blattella germanica and is involved in TGF-ß, ecdysone, and MEKRE93 pathways, contributing to the activation of Kr-h1 and E93 expression. In D. melanogaster, Nejire's involvement in the ecdysone pathway in pre-metamorphic stages is conserved, whereas the TGF-ß pathway has only been described in the embryo. CBP role in ecdysis pathway and in the activation of Kr-h1 and E93 expression is described here for the first time.

CONCLUSIONS

Studies in D. melanogaster may have been suggestive that CBP functions in insects are concentrated in the embryo. Results obtained in B. germanica indicate, however, that CBP have diverse and important functions in post-embryonic development and metamorphosis, especially regarding endocrine signaling.

GENERAL SIGNIFICANCE

Further research into a higher diversity of models will probably reveal that the multiple post-embryonic roles of CBP observed in B. germanica are general in insects.

Acetylations of Ftz-F1 and histone H4K5 are required for the fine-tuning of ecdysone biosynthesis during Drosophila metamorphosis

The molting during Drosophila development is tightly regulated by the ecdysone hormone. Several steps of the ecdysone biosynthesis have been already identified but the regulation of the entire process has not been clarified yet. We have previously reported that dATAC histone acetyltransferase complex is necessary for the steroid hormone biosynthesis process. To reveal possible mechanisms controlled by dATAC we made assumptions that either dATAC may influence directly the transcription of Halloween genes involved in steroid hormone biosynthesis or it may exert an indirect effect on it by acetylating the Ftz-F1 transcription factor which regulates the transcription of steroid converting genes. Here we show that the lack of dATAC complex results in increased mRNA level and decreased protein level of Ftz-F1. In this context, decreased mRNA and increased protein levels of Ftz-F1 were detected upon treatment of Drosophila S2 cells with histone deacetylase inhibitor trichostatin A. We showed that Ftz-F1, the transcriptional activator of Halloween genes, is acetylated in S2 cells. In addition, we found that ecdysone biosynthetic Halloween genes are transcribed in S2 cells and their expression can be influenced by deacetylase inhibitors. Furthermore, we could detect H4K5 acetylation at the regulatory regions of disembodied and shade Halloween genes, while H3K9 acetylation is absent on these genes. Based on our findings we conclude that the dATAC HAT complex might play a dual regulatory role in Drosophila steroid hormone biosynthesis through the acetylation of Ftz-F1 protein and the regulation of the H4K5 acetylation at the promoters of Halloween genes.

Fertility preservation in a family with a novel NR5A1 mutation

The common phenotype of nuclear receptor superfamily 5, group A, member 1 (NR5A1) gene mutations in 46,XY is gonadal dysgenesis without adrenal deficiency. Though the phenotype of gonadal dysgenesis is variable, ranging from complete female to normal male genitalia, an asymptomatic 46,XY male is rare. Preserved fertility has so far been described in only three affected 46,XY males with different mutations, but no functional analysis of these mutations has been performed. Here, we report on male siblings with hypospadias and their asymptomatic father in whom we identified a heterozygous NR5A1 mutation of c.910G>A, p.E304K. Western blotting and subcellular localization revealed no significant difference between the wild type (WT) and E304K. Electrophoretic mobility shift assay experiments showed that E304K abrogated DNA-binding ability. E304K reduced transactivation and had no dominant negative effect. In conclusion, we report on a novel hypomorphic NR5A1 mutation, which may be associated with the phenotype of the family.

Acidic residue Glu199 increases SUMOylation level of nuclear hormone receptor NR5A1

Steroidogenic factor 1 (NR5A1/SF1) is a well-known master regulator in controlling adrenal and sexual development, as well as regulating numerous genes involved in adrenal and gonadal steroidogenesis. Several studies including ours have demonstrated that NR5A1 can be SUMOylated on lysine 194 (K194, the major site) and lysine 119 (K119, the minor site), and the cycle of SUMOylation regulates NR5A1’s transcriptional activity. An extended consensus negatively charged amino acid-dependent SUMOylation motif (NDSM) enhances the specificity of substrate modification by SUMO has been reported; however, the mechanism of NDSM for NR5A1 remains to be clarified. In this study, we investigated the functional significance of the acidic residue located downstream from the core consensus SUMO site of NR5A1. Here we report that E199A (glutamic acid was replaced with alanine) of NR5A1 reduced, but not completely abolished, its SUMOylation level. We next characterized the functional role of NR5A1 E199A on target gene expression and protein levels. We found that E199A alone, as well as combination with K194R, increased Mc2r and Cyp19a1 reporter activities. Moreover, E199A alone as well as combination with K194R enhanced NR5A1-mediated STAR protein levels in mouse adrenocortical cancer Y1 cells. We also observed that E199A increased interaction of NR5A1 with CDK7 and SRC1. Overall, we provide the evidence that the acidic residue (E199) located downstream from the core consensus SUMO site of NR5A1 is, at least in part, required for SUMOylation of NR5A1 and for its mediated target gene and protein expression.

Lhcgr Expression in Granulosa Cells: Roles for PKA-Phosphorylated β-Catenin, TCF3, and FOXO1

Ovarian follicles lacking FSH or FSH receptors fail to progress to a preovulatory stage, resulting in infertility. One hallmark of the preovulatory follicle is the presence of luteinizing hormone/choriogonadotropin receptors (LHCGR) on granulosa cells (GCs). However, the mechanisms by which FSH induces Lhcgr gene expression are poorly understood. Our results show that protein kinase A (PKA) and phosphoinositide 3-kinase (PI3K)/AKT pathways are required for FSH to activate both the murine Lhcgr-luciferase reporter and expression of Lhcgr mRNA in rat GCs. Based on results showing that an adenovirus (Ad) expressing a steroidogenic factor 1 (SF1) mutant that cannot bind β-catenin abolished FSH-induced Lhcgr mRNA, we evaluated the role of β-catenin in the regulation of Lhcgr gene expression. FSH promoted the PKA-dependent, PI3K-independent phosphorylation of β-catenin on Ser552 and Ser665. FSH activated the β-catenin/T-cell factor (TCF) artificial promoter-reporter TOPFlash via a PKA-dependent, PI3K-independent pathway, and dominant-negative (DN) TCF abolished FSH-activated Lhcgr-luciferase reporter and induction of Lhcgr mRNA. Microarray analysis of GCs treated with Ad-DN-TCF and FSH identified the Lhcgr as the most down-regulated gene. Chromatin immunoprecipitation results placed β-catenin phosphorylated on Ser552 and Ser675 and SF1 on the Lhcgr promoter in FSH-treated GCs; TCF3 was constitutively associated with the Lhcgr promoter. Transduction with an Ad-phospho-β-catenin mutant (Ser552/665/Asp) enhanced Lhcgr mRNA expression in FSH-treated cells greater than 3-fold. Finally, we identified a recognized PI3K/AKT target, forkhead box O1, as a negative regulator of Lhcgr mRNA expression. These results provide new understanding of the complex regulation of Lhcgr gene expression in GCs.

Functional conservation of Drosophila FTZ-F1 and its mammalian homologs suggests ligand-independent regulation of NR5A family transcriptional activity

Drosophila Ftz-F1 is an orphan nuclear receptor required for segmentation and metamorphosis. Its mammalian orthologs, SF-1 and LRH-1, function in sexual development and homeostasis, and have been implicated in stem cell pluripotency maintenance and tumorigenesis. These NR5A family members bind DNA as monomers and strongly activate transcription. However, controversy exists as to whether their activity is regulated by ligand-binding. Structural evidence suggested that SF-1 and human LRH-1 bind regulatory ligands, but mouse LRH-1 and Drosophila FTZ-F1 are active in the absence of ligand. We found that Dm-Ftz-F1 and mLRH-1, thought not to bind ligand, or mSF-1 and hLRH-1, predicted to bind ligand, each efficiently rescued the defects of Drosophila ftz-f1 mutants. Further, each correctly activated expression of a Dm-Ftz-F1 target gene in Drosophila embryos. The functional equivalence of ftz-f1 orthologs in these sensitive in vivo assays argues against specific activating ligands for NR5A family members.

cAMP-stimulated transcription of DGKθ requires steroidogenic factor 1 and sterol regulatory element binding protein 1

Diacylglycerol kinase (DGK)θ is a lipid kinase that phosphorylates diacylglycerol to form phosphatidic acid (PA). We have previously shown that PA is a ligand for the nuclear receptor steroidogenic factor 1 (SF1) and that cAMP-stimulated expression of SF1 target genes requires DGKθ. In this study, we sought to investigate the role of cAMP signaling in regulating DGKθ gene expression. Real time RT-PCR and Western blot analysis revealed that dibutyryl cAMP (Bt2cAMP) increased the mRNA and protein expression, respectively, of DGKθ in H295R human adrenocortical cells. SF1 and sterol regulatory element binding protein 1 (SREBP1) increased the transcriptional activity of a reporter plasmid containing 1.5 kb of the DGKθ promoter fused to the luciferase gene. Mutation of putative cAMP responsive sequences abolished SF1- and SREBP-dependent DGKθ reporter gene activation. Consistent with this finding, chromatin immunoprecipitation assay demonstrated that Bt2cAMP signaling increased the recruitment of SF1 and SREBP1 to the DGKθ promoter. Coimmunoprecipitation assay revealed that SF1 and SREBP1 interact, suggesting that the two transcription factors form a complex on the DGKθ promoter. Finally, silencing SF1 and SREBP1 abolished cAMP-stimulated DGKθ expression. Taken together, we demonstrate that SF1 and SREBP1 activate DGKθ transcription in a cAMP-dependent manner in human adrenocortical cells.

Acid ceramidase (ASAH1) represses steroidogenic factor 1-dependent gene transcription in H295R human adrenocortical cells by binding to the receptor

Adrenocorticotropin (ACTH) signaling increases glucocorticoid production by promoting the interaction of transcription factors and coactivator proteins with the promoter of steroidogenic genes. The nuclear receptor steroidogenic factor 1 (SF-1) is essential for steroidogenic gene transcription. Sphingosine (SPH) is a ligand for SF-1. Moreover, suppression of expression of acid ceramidase (ASAH1), an enzyme that produces SPH, increases the transcription of multiple steroidogenic genes. Given that SF-1 is a nuclear protein, we sought to define the molecular mechanisms by which ASAH1 regulates SF-1 function. We show that ASAH1 is localized in the nuclei of H295R adrenocortical cells and that cyclic AMP (cAMP) signaling promotes nuclear sphingolipid metabolism in an ASAH1-dependent manner. ASAH1 suppresses SF-1 activity by directly interacting with the receptor. Chromatin immunoprecipitation (ChIP) assays revealed that ASAH1 is recruited to the promoter of various SF-1 target genes and that ASAH1 and SF-1 colocalize on the same promoter region of the CYP17A1 and steroidogenic acute regulatory protein (StAR) genes. Taken together, these results demonstrate that ASAH1 is a novel coregulatory protein that represses SF-1 function by directly binding to the receptor on SF-1 target gene promoters and identify a key role for nuclear lipid metabolism in regulating gene transcription.

The LIM domain protein FHL2 interacts with the NR5A family of nuclear receptors and CREB to activate the inhibin-α subunit gene in ovarian granulosa cells

Nuclear receptor transcriptional activity is enhanced by interaction with coactivators. The highly related nuclear receptor 5A (NR5A) subfamily members liver receptor homolog 1 and steroidogenic factor 1 bind to and activate several of the same genes, many of which are important for reproductive function. To better understand transcriptional activation by these nuclear receptors, we sought to identify interacting proteins that might function as coactivators. The LIM domain protein four and a half LIM domain 2 (FHL2) was identified as interacting with the NR5A receptors in a yeast two-hybrid screen of a human ovary cDNA library. FHL2, and the closely related FHL1, are both expressed in the rodent ovary and in granulosa cells. Small interfering RNA-mediated knockdown of FHL1 and FHL2 in primary mouse granulosa cells reduced expression of the NR5A target genes encoding inhibin-α and P450scc. In vitro assays confirmed the interaction between the FHL and NR5A proteins and revealed that a single LIM domain of FHL2 is sufficient for this interaction, whereas determinants in both the ligand binding domain and DNA binding domain of NR5A proteins are important. FHL2 enhances the ability of both liver receptor homolog 1 and steroidogenic factor 1 to activate the inhibin-α subunit gene promoter in granulosa cells and thus functions as a transcriptional coactivator. FHL2 also interacts with cAMP response element-binding protein and substantially augments activation of inhibin gene expression by the combination of NR5A receptors and forskolin, suggesting that FHL2 may facilitate integration of these two signals. Collectively these results identify FHL2 as a novel coactivator of NR5A nuclear receptors in ovarian granulosa cells and suggest its involvement in regulating target genes important for mammalian reproduction.

Involvement of transcription factor GATA-4 in regulation of CYP19 gene during folliculogenesis and luteinization in buffalo ovary

CYP19 gene encode aromatase, the key enzyme of estrogen biosynthesis, is regulated in species- and tissue-specific manner by alternate use of different promoters. Previously, we have reported the cloning and characterization of tissue-specific promoter and transcripts in buffalo ovary and placenta. In human and rat ovary, FSH induces the phosphorylation of transcription factor CREB (cAMP response element binding protein) through PKA pathway which binds to cAMP response element like sequence (CLS) in CYP19 gene ovarian promoter. However, in buffalo as well as in bovine, in silico analysis of ovary specific promoter sequence identified a single base pair deletion in CLS site and is designated as CLS-like sequence. To understand if CLS with a point mutation is still a functional cis-element and is involved in FSH stimulated transactivation of CYP19 gene in buffalo ovary, the present study was thus aimed to functionally characterize the role of buffalo CLS in CYP19 gene transactivation. We also studied the involvement of GATA-4, having consensus binding sites in CYP19 gene ovarian promoter in the vicinity of CLS during different stages of the buffalo estrus cycle. Reporter construct analyses and EMSA results showed that CLS is playing no significant role in CYP19 gene regulation in buffalo ovary. Real time absolute quantification of GATA-4 showed the differential expression of GATA-4 mRNA during folliculogenesis and luteinization with significantly higher transcript abundance in large follicle in comparison to other tissues. Western blot analysis of granulosa cells nuclear protein isolated from different stage of follicular development (small and large follicles) and differentiation (corpus luteum) showed that abundance of phosphorylated GATA-4 (Ser261) was significantly higher in granulosa cell nuclear protein of large follicles as compared to small follicles and corpora lutea. Interestingly, binding studies using ChIP showed significantly enhanced binding to the CYP19 gene promoter in large follicle which was seen to be declined in the luteal tissue. Similar results were obtained in the in vitro experiments as well. Finally, RNAi experiments were performed to validate the involvement of GATA-4 in CYP19 gene regulation. Results of RNAi showed that knockdown of GATA-4 mRNA significantly declined CYP19 gene mRNA as well as 17β-estradiol contents. In conclusion, result of the present study indicated that that in the absence of consensus CRE (cAMP response element); GATA-4 could be a downstream effector of cAMP/PKA pathway in regulation of CYP19 gene during folliculogenesis and luteinization.

Death-associated protein 6 (Daxx) mediates cAMP-dependent stimulation of Cyp11a1 (P450scc) transcription

SF-1 is a key transcription factor for all steroidogenic genes. It up-regulates the expression of the steroidogenic Cyp11a1 gene in the adrenal in a pathway stimulated by cAMP through HIPK3-mediated JNK/c-Jun phosphorylation. In the present study, we have investigated the factors mediating cAMP-dependent HIPK3 action to potentiate the activity of SF-1 for Cyp11a1 transcription in mouse adrenocortical Y1 cells. We found Daxx, a HIPK kinase substrate in the apoptosis pathway, was phosphorylated by HIPK3 at Ser-669 in response to cAMP stimulation. Daxx participated in SF-1-dependent Cyp11a1 expression as shown by experiments involving both overexpression and down-regulation via a dominant negative Daxx mutant. The S669A mutant of Daxx, which could not be phosphorylated by HIPK3, lost the ability to potentiate SF-1 activity for Cyp11a1 expression. The enhancement of SF-1 activity by Daxx required JNK and c-Jun phosphorylation. Thus, Daxx functioned as a signal transducer linking cAMP-stimulated HIPK3 activity with JNK/c-Jun phosphorylation and SF-1-dependent Cyp11a1 transcription for steroid synthesis.

GATA transcription factors regulate LHβ gene expression

The GATA family of transcription factors are critical determinants of cell differentiation as well as regulation of adult gene expression throughout the reproductive axis. Within the anterior pituitary gland, GATA factors have been shown to increase glycoprotein α-subunit gene promoter activity; however, nothing has been known about the impact of these factors on expression of the gonadotropin β-subunits. In this study, we demonstrate expression of both GATA2 and GATA4 in primary mouse gonadotropes and the gonadotrope cell line, LβT2. Based on the transient transfection in fibroblast cells, GATA factors increase LH β-subunit gene (LHβ) promoter activity alone and in synergy with the orphan nuclear receptors steroidogenic factor-1 (SF-1) and liver receptor homologue-1 (LRH-1). The GATA response was localized to a DNA regulatory region at position -101 in the rat LHβ gene promoter which overlaps with a previously described cis-element for pituitary homeobox-1 (Pitx1) and is flanked by two SF-1/LRH-1 regulatory sites. As determined by gel shift, GATA and Pitx1 can compete for binding to this element. Furthermore, mutation analysis revealed a requirement for both the GATA/Pitx1 and the SF-1/LRH-1 cis-elements in order to achieve synergy. These studies identify a novel role for GATA transcription factors in the pituitary and reveal additional molecular mechanisms by which precise modulation of LHβ gene expression can be achieved.

Steroidogenic factor-1 is required for TGF-beta3-mediated 17beta-estradiol synthesis in mouse ovarian granulosa cells

The TGF-β superfamily members are indicated to play key roles in ovarian follicular development, such as granulosa cell proliferation, estrogens, and progesterone production. However, little is known about the roles of TGF-β3 in follicular development. In this study, we found that TGF-β3 was predominantly expressed in granulosa cells of mouse ovarian follicles, and it significantly promoted 17β-estradiol (E(2)) release in a dose-dependent manner. The orphan nuclear receptor steroidogenic factor-1 (SF-1) was required in TGF-β3-induced Cyp19a1 (a key rate-limiting enzyme for estrogen biosynthesis) expression and E(2) release. Additionally, TGF-β3 enhanced the binding of SF-1 to endogenous ovary-specific Cyp19a1 type II promoter, as evidenced by chromatin immunoprecipitation assays. The enhanced effect of SF-1 by TGF-β3 may be mediated through functional interactions between SF-1 and mothers against decapentaplegic homolog (Smad)3 (a mediator of TGF-β signaling pathway), because disruption of the interaction abolished the synergistic effects of SF-1, Smad3, and TGF-β3 on Cyp19a1 mRNA expression. RNA interference and chromatin immunoprecipitation studies also demonstrated that Smad3 was required for SF-1 binding to Cyp19a1 type II promoter and activation of Cyp19a1. Smad3 thus acts as a point of convergence that involves integration of SF-1 and TGF-β signaling in affecting E(2) production. Taken together, our data provide mechanistic insights into the roles of SF-1 in TGF-β3-mediated E(2) synthesis. Understanding of potential cross-points between extracellular signals affecting estrogen production will help to discover new therapeutic targets in estrogen-related diseases.

Coactivation of SF-1-mediated transcription of steroidogenic enzymes by Ubc9 and PIAS1

Steroidogenic factor-1 (SF-1) is a nuclear orphan receptor, which is essential for adrenal development and regulation of steroidogenic enzyme expression. SF-1 is posttranslationally modified by small ubiquitin-related modifier-1 (SUMO-1), thus mostly resulting in attenuation of transcription. We investigated the role of sumoylation enzymes, Ubc9 and protein inhibitors of activated STAT1 (PIAS1), in SF-1-mediated transcription of steroidogenic enzyme genes in the adrenal cortex. Coimmunoprecipitation assays showed that both Ubc9 and PIAS1 interacted with SF-1. Transient transfection assays in adrenocortical H295R cells showed Ubc9 and PIAS1 potentiated SF-1-mediated transactivation of reporter constructs containing human CYP17, CYP11A1, and CYP11B1 but not CYP11B2 promoters. Reduction of endogenous Ubc9 and PIAS1 by introducing corresponding small interfering RNA significantly reduced endogenous CYP17, CYP11A1, and CYP11B1 mRNA levels, indicating that they normally function as coactivators of SF-1. Wild type and sumoylation-inactive mutants of Ubc9 and PIAS1 can similarly enhance the SF-1-mediated transactivation of the CYP17 gene, indicating that the coactivation potency of Ubc9 and PIAS1 is independent of sumoylation activity. Chromatin immunoprecipitation assays demonstrated that SF-1, Ubc9, and PIAS1 were recruited to an endogenous CYP17 gene promoter in the context of chromatin in vivo. Immunohistochemistry and Western blotting showed that SF-1, Ubc9, and PIAS1 were expressed in the nuclei of the human adrenal cortex. In cortisol-producing adenomas, the expression pattern of SF-1 and Ubc9 were markedly increased, whereas that of PIAS1 was decreased compared with adjacent normal adrenals. These results showed the physiological roles of Ubc9 and PIAS1 as SF-1 coactivators beyond sumoylation enzymes in adrenocortical steroidogenesis and suggested their possible pathophysiological roles in human cortisol-producing adenomas.

The AP-1 family member FOS blocks transcriptional activity of the nuclear receptor steroidogenic factor 1

Steroid production in the adrenal zona glomerulosa is under the control of angiotensin II (Ang II), which, upon binding to its receptor, activates protein kinase C (PKC) within these cells. PKC is a potent inhibitor of the steroidogenic enzyme CYP17. We have demonstrated that, in the ovary, PKC activates expression of FOS, a member of the AP-1 family, and increased expression of this gene is linked to CYP17 downregulation. However, the pathway and the molecular mechanism responsible for the inhibitory effect of PKC on CYP17 expression are not defined. Herein, we demonstrated that Ang II inhibited CYP17 through PKC and ERK1/2-activated FOS and that blocking FOS expression decreased PKC-mediated inhibition. Although CYP17 transcription was activated by the nuclear receptor SF-1, expression of FOS resulted in a decrease in SF-1-mediated gene transcription. FOS physically interacted with the hinge region of SF-1 and modulated its transactivity, thus preventing binding of cofactors such as SRC1 and CBP, which were necessary to fully activate CYP17 transcription. Collectively, these results indicate a new regulatory mechanism for SF-1 transcriptional activity that might influence adrenal zone-specific expression of CYP17, a mechanism that can potentially be applied to other steroidogenic tissues.

Minireview: steroidogenic factor 1: its roles in differentiation, development, and disease

The orphan nuclear receptor steroidogenic factor 1 (SF-1, also called Ad4BP, encoded by the NR5A1 gene) is an essential regulator of endocrine development and function. Initially identified as a tissue-specific transcriptional regulator of cytochrome P450 steroid hydroxylases, studies of both global and tissue-specific knockout mice have demonstrated that SF-1 is required for the development of the adrenal glands, gonads, and ventromedial hypothalamus and for the proper functioning of pituitary gonadotropes. Many genes are transcriptionally regulated by SF-1, and many proteins, in turn, interact with SF-1 and modulate its activity. Whereas mice with heterozygous mutations that disrupt SF-1 function have only subtle abnormalities, humans with heterozygous SF-1 mutations can present with XY sex reversal (i.e. testicular failure), ovarian failure, and occasionally adrenal insufficiency; dysregulation of SF-1 has been linked to diseases such as endometriosis and adrenocortical carcinoma. The current state of knowledge of this important transcription factor will be reviewed with a particular emphasis on the pioneering work on SF-1 by the late Keith Parker.

Molecular aspects of steroidogenic factor 1 (SF-1)

Steroidogenic factor 1 (SF-1, also called Ad4BP and NR5A1) is a nuclear receptor with critical roles in steroidogenic tissues, as well as in the brain and pituitary. In particular, SF-1 has emerged as an essential regulator of adrenal and gonadal functions and development. In the last few years, our knowledge on SF-1 has increased considerably at all levels, from the gene to the protein, and on its specific roles in different physiological processes. In this review, we discuss the current understanding on SF-1 with focus on the parameters that control the transcriptional capacity of SF-1 and the mechanisms that ensure proper stage- and tissue-specific expression of the gene encoding SF-1.

Transcriptional regulation of steroidogenic genes: STARD1, CYP11A1 and HSD3B

Expression of the genes that mediate the first steps in steroidogenesis, the steroidogenic acute regulatory protein (STARD1), the cholesterol side-chain cleavage enzyme, cytochrome P450scc (CYP11A1) and 3beta-hydroxysteroid dehydrogenase/Delta5-Delta4 isomerase (HSD3B), is tightly controlled by a battery of transcription factors in the adrenal cortex, the gonads and the placenta. These genes generally respond to the same hormones that stimulate steroid production through common pathways such as cAMP signaling and common actions on their promoters by proteins such as NR5A and GATA family members. However, there are distinct temporal, tissue and species-specific differences in expression between the genes that are defined by combinatorial regulation and unique promoter elements. This review will provide an overview of the hormonal and transcriptional regulation of the STARD1, CYP11A1 and specific steroidogenic HSD3B genes in the adrenal, testis, ovary and placenta and discuss the current knowledge regarding the key transcriptional factors involved.

SUMOylation inhibits SF-1 activity by reducing CDK7-mediated serine 203 phosphorylation

Steroidogenic factor 1 (SF-1) is an orphan nuclear receptor selectively expressed in the adrenal cortex and gonads, where it mediates the hormonal stimulation of multiple genes involved in steroid hormone biosynthesis. SF-1 is the target of both phosphorylation and SUMOylation, but how these modifications interact or contribute to SF-1 regulation of endogenous genes remains poorly defined. We found that SF-1 is selectively SUMOylated at K194 in Y1 adrenocarcinoma cells and that although SUMOylation does not alter the subcellular localization of SF-1, the modification inhibits the ability of SF-1 to activate target genes. Notably, whereas SF-1 SUMOylation is independent of S203 phosphorylation and is unaffected by adrenocorticotropin (ACTH) treatment, loss of SUMOylation leads to enhanced SF-1 phosphorylation at serine 203. Furthermore, preventing SF-1 SUMOylation increases the mRNA and protein levels of multiple steroidogenic enzyme genes. Analysis of the StAR promoter indicates that blockade of SF-1 SUMOylation leads to an increase in overall promoter occupancy but does not alter the oscillatory recruitment dynamics in response to ACTH. Notably, we find that CDK7 binds preferentially to the SUMOylation-deficient form of SF-1 and that CDK7 inhibition reduces phosphorylation of SF-1. Based on these observations, we propose a coordinated modification model in which inhibition of SF-1-mediated transcription by SUMOylation in adrenocortical cancer cells is mediated through reduced CDK7-induced phosphorylation of SF-1.

Regulation of Kruppel-like factor 4, 9, and 13 genes and the steroidogenic genes LDLR, StAR, and CYP11A in ovarian granulosa cells

Kruppel-like factors (KLFs) are important Sp1-like eukaryotic transcriptional proteins. The LDLR, StAR, and CYP11A genes exhibit GC-rich Sp1-like sites, which have the potential to bind KLFs in multiprotein complexes. We now report that KLF4, KLF9, and KLF13 transcripts are expressed in and regulate ovarian cells. KLF4 and 13, but not KLF9, mRNA expression was induced and then repressed over time (P < 0.001). Combined LH and IGF-I stimulation increased KLF4 mRNA at 2 h (P < 0.01), whereas LH decreased KLF13 mRNA at 6 h (P < 0.05), and IGF-I reduced KLF13 at 24 h (P < 0.01) compared with untreated control. KLF9 was not regulated by either hormone. Transient transfection of KLF4, KLF9, and KLF13 suppressed LDLR/luc, StAR/luc, and CYP11A/luc by 80-90% (P < 0.001). Histone-deacetylase (HDAC) inhibitors stimulated LDLR/luc five- to sixfold and StAR/luc and CYP11A/luc activity twofold (P < 0.001) and partially reversed suppression by all three KLFs (P < 0.001). Deletion of the zinc finger domain of KLF13 abrogated repression of LDLR/luc. Lentiviral overexpression of the KLF13 gene suppressed LDLR mRNA (P < 0.001) and CYP11A mRNA (P = 0.003) but increased StAR mRNA (P = 0.007). Collectively, these data suggest that KLFs may recruit inhibitory complexes containing HDAC corepressors, thereby repressing LDLR and CYP11A transcription. Conversely, KLF13 may recruit unknown coactivators or stabilize StAR mRNA, thereby explaining enhancement of in situ StAR gene expression. These data introduce new potent gonadal transregulators of genes encoding proteins that mediate sterol uptake and steroid biosynthesis.

CCAAT/enhancer binding protein beta, but not steroidogenic factor-1, modulates the phthalate-induced dysregulation of rat fetal testicular steroidogenesis

Prolonged in utero exposure of fetal male rats to dibutyl phthalate (DBP) can result in a feminized phenotype characterized by malformed epididymides, hypospadias, cryptorchidism, and retained thoracic nipples, among others. These symptoms likely result, in part, from decreased expression of steroidogenic enzymes and, therefore, reduced testosterone biosynthesis. However, the molecular mechanisms involved in these changes in gene expression profiles are unknown. To understand these mechanisms in rats, in vivo DNase footprinting was adapted to provide a semiquantitative map of changes in DNA-protein interactions in the promoter region of steroidogenic genes, including steroidogenic acute regulatory, scavenger receptor B-1, cytochrome P450 side chain cleavage, and cytochrome P450 17A1, that are down-regulated after an in utero DBP exposure. Regions with altered DNase protection were coordinated with a specific DNA binding protein event by EMSA, and binding activity confirmed with chromatin immunoprecipitation. Results demonstrated altered DNase protection at regions mapping to CCAAT/enhancer binding protein beta (c/ebp beta) and steroidogenic factor-1 (SF-1). Chromatin immunoprecipitation confirmed declines in DNA-protein interactions of c/ebp beta in DBP treated animals, whereas SF-1 was reduced in both diethyl phthalate (nontoxic) and DBP (toxic) treatments. These results suggest that inhibition of c/ebp beta, and not SF-1, is critical in DBP induced inhibition of steroidogenic genes. In addition, these observations suggest a pathway redundancy in the regulation of steroidogenesis in fetal testis. In conclusion, this study presents a snapshot of changes in the structure of transcriptional machinery and proposes a mechanism of action resulting from DBP exposure.

Haplotype analysis of CYP11A1 identifies promoter variants associated with breast cancer risk

The CYP11A1 gene encodes the cholesterol side chain cleavage enzyme that catalyzes the initial and rate-limiting step of steroidogenesis. A large number of epidemiologic studies have implicated the duration and degree of endogenous estrogen exposure in the development of breast cancer in women. Here, we conduct a systematic investigation of the role of genetic variation of the CYP11A1 gene in breast cancer risk in a study of 1193 breast cancer cases and 1310 matched controls from the Shanghai Breast Cancer Study. We characterize the genetic architecture of the CYP11A1 gene in a Chinese study population. We then genotype tagging polymorphisms to capture common variation at the locus for tests of association. Variants designating a haplotype encompassing the gene promoter are significantly associated with both increased expression (P = 1.6e-6) and increased breast cancer risk: heterozygote age-adjusted odds ratio (OR), 1.51 [95% confidence interval (95% CI), 1.19-1.91]; homozygote age-adjusted OR, 2.94 (95% CI, 1.22-7.12), test for trend, P = 5.0e-5. Among genes controlling endogenous estrogen metabolism, CYP11A1 harbors common variants that may influence expression to significantly modify risk of breast cancer.

Histone deacetylase inhibitors reduce steroidogenesis through SCF-mediated ubiquitination and degradation of steroidogenic factor 1 (NR5A1)

Histone deacetylase (HDAC) inhibitors such as trichostatin A and valproic acid modulate transcription of many genes by inhibiting the activities of HDACs, resulting in the remodeling of chromatin. Yet this effect is not universal for all genes. Here we show that HDAC inhibitors suppressed the expression of steroidogenic gene CYP11A1 and decreased steroid secretion by increasing the ubiquitination and degradation of SF-1, a factor important for the transcription of all steroidogenic genes. This was accompanied by increased expression of Ube2D1 and SKP1A, an E2 ubiquitin conjugase and a subunit of the E3 ubiquitin ligase in the Skp1/Cul1/F-box protein (SCF) family, respectively. Reducing SKP1A expression with small interfering RNA resulted in recovery of SF-1 levels, demonstrating that the activity of SCF E3 ubiquitin ligase is required for the SF-1 degradation induced by HDAC inhibitors. Overexpression of exogenous SF-1 restored steroidogenic activities even in the presence of HDAC inhibitors. Thus, increased SF-1 degradation is the cause of the reduction in steroidogenesis caused by HDAC inhibitors. The increased SKP1A expression and SCF-mediated protein degradation could be the mechanism underlying the mode of action of HDAC inhibitors.

Cyclic AMP-stimulated interaction between steroidogenic factor 1 and diacylglycerol kinase theta facilitates induction of CYP17

In the human adrenal cortex, adrenocorticotropin (ACTH) activates CYP17 transcription by promoting the binding of the nuclear receptor steroidogenic factor 1 (SF1) (Ad4BP, NR5A1) to the promoter. We recently found that sphingosine is an antagonist for SF1 and inhibits cyclic AMP (cAMP)-dependent CYP17 gene transcription. The aim of the current study was to identify phospholipids that bind to SF1 and to characterize the mechanism by which ACTH/cAMP regulates the biosynthesis of this molecule(s). Using tandem mass spectrometry, we show that in H295R human adrenocortical cells, SF1 is bound to phosphatidic acid (PA). Activation of the ACTH/cAMP signal transduction cascade rapidly increases nuclear diacylglycerol kinase (DGK) activity and PA production. PA stimulates SF1-dependent transcription of CYP17 reporter plasmids, promotes coactivator recruitment, and induces the mRNA expression of CYP17 and several other steroidogenic genes. Inhibition of DGK activity attenuates the binding of SF1 to the CYP17 promoter, and silencing of DGK-theta expression inhibits cAMP-dependent CYP17 transcription. LXXLL motifs in DGK-theta mediate a direct interaction of SF1 with the kinase and may facilitate binding of PA to the receptor. We conclude that ACTH/cAMP stimulates PA production in the nucleus of H295R cells and that this increase in PA concentrations facilitates CYP17 induction.

Dephosphorylation of TORC initiates expression of the StAR gene

Cyclic AMP responsive element (CRE) binding protein (CREB) is known to activate transcription when its Ser133 is phosphorylated. However, transducer of regulated CREB activity (TORC), a CREB specific co-activator, upregulates CREB activity in a phospho-Ser133-independent manner. Interestingly, TORC is also regulated by phosphorylation; the phospho-form is inactive, and the dephospho-form active. When PKA phosphorylates CREB, it inhibits TORC kinases simultaneously and accelerates dephosphorylation of TORC. We show in this report that staurosporine, a kinase inhibitor, induces the expression of the StAR gene in Y1 adrenocortical cells, possibly a result of an increase in the population of dephospho-TORC. The expression of the StAR gene is known to be regulated by SF-1 and CREB, and the co-activators CBP/p300 may mediate the actions of both factors. Our experiments using KG501, a disruptor of the interaction between phospho-CREB and CBP/p300, also support the importance of TORC in the regulation of StAR gene expression.

Cyclic AMP stimulates SF-1-dependent CYP11A1 expression through homeodomain-interacting protein kinase 3-mediated Jun N-terminal kinase and c-Jun phosphorylation

Steroids are synthesized in adrenal glands and gonads under the control of pituitary peptides. These peptides bind to cell surface receptors to activate the cyclic AMP (cAMP) signaling pathway leading to an increase of steroidogenic gene expression. Exactly how cAMP activates steroidogenic gene expression is not clear, except for the knowledge that transcription factor SF-1 plays a key role. Investigating the factors participating in SF-1 action, we found that c-Jun and homeodomain-interacting protein kinase 3 (HIPK3) were required for basal and cAMP-stimulated expression of one major steroidogenic gene, CYP11A1. HIPK3 enhanced SF-1 activity, and c-Jun was required for the functional interaction of HIPK3 with SF-1. Furthermore, after cAMP stimulation, both c-Jun and Jun N-terminal kinase (JNK) were phosphorylated through HIPK3. These phosphorylations were important for SF-1 activity and CYP11A1 expression. Thus, we have defined HIPK3-mediated JNK activity and c-Jun phosphorylation as important events that increase SF-1 activity for CYP11A1 transcription in response to cAMP. This finding has linked three common factors, HIPK3, JNK, and c-Jun, to the cAMP signaling pathway leading to increased steroidogenic gene expression.

International Union of Pharmacology. LXVI. Orphan nuclear receptors

Half of the members of the nuclear receptors superfamily are so-called "orphan" receptors because the identity of their ligand, if any, is unknown. Because of their important biological roles, the study of orphan receptors has attracted much attention recently and has resulted in rapid advances that have helped in the discovery of novel signaling pathways. In this review we present the main features of orphan receptors, discuss the structure of their ligand-binding domains and their biological functions. The paradoxical existence of a pharmacology of orphan receptors, a rapidly growing and innovative field, is highlighted.

Transcriptional activation of the steroidogenic acute regulatory protein (StAR) gene: GATA-4 and CCAAT/enhancer-binding protein beta confer synergistic responsiveness in hormone-treated rat granulosa and HEK293 cell models

Steroidogenic acute regulatory protein (StAR) mediates translocation of cholesterol to the inner membranes of steroidogenic mitochondria, where it serves as a substrate for steroid synthesis. Transcription of StAR in the gonads and adrenal cells is upregulated by trophic hormones, involves downstream signaling pathways and a cohort of trans-factors acting as activators or suppressors of StAR transcription. This study suggests that a 21 basepair long sequence positioned at -81/-61 of the murine StAR promoter is sufficient to confer a robust hormonal activation of transcription in ovarian granulosa cells treated with FSH. We show that recombinant GATA-4 and CCAAT/enhancer-binding protein beta (C/EBPbeta) bind to the promoter at -66/-61 and -81/-70 and activate transcription of a reporter gene when co-expressed in heterologous human embryonic kidney 293 (HEK293) cells. In this cell model, C/EBPbeta and GATA-4 synergize in a sequence dependent manner and p300/CBP further maximizes their joint activities. Inhibitors of the transcriptional activators, such as liver-enriched inhibiting protein (C/EBPbeta-LIP), Friend of GATA-4 (FOG-2) protein and the viral E1A protein abolished the respective factor-dependent activities in HEK293 cells. Binding assays suggest that a dual binding of C/EBPbeta and GATA-4 to the promoter depends on the molar ratio of the factors present while demonstrating GATA-4 predominant association with the promoter DNA. This pattern may reflect on StAR expression at the time of corpus luteum formation when C/EBPbeta levels peak, as does StAR expression.

Direct binding of TReP-132 with TdT results in reduction of TdT activity

N regions at the junction of V, D and J DNA segments are synthesized with large protein complexes including terminal deoxynucleotidyltransferase (TdT) during V(D)J recombination in B- or T-cells. TdT directly binds to TdIF1, TdIF2, PCNA and the Ku70/86 heterodimer. Using a yeast two-hybrid system, we isolated a cDNA clone encoding the gene for TReP-132, which is involved in P450scc gene expression in steroid-hormone-producing cells or lymphoid cells. Interaction between TReP-132 and TdIF1 was confirmed by pull-down assay and immunoprecipitation assay using specific antibodies against TReP-132 both in vitro and in vivo. TdT also directly bound to TReP-132 through its confined N-terminal region. Furthermore, the co-expression of TdIF1 and TReP-132 or TdT and TReP-132 in COS7 cells showed that these proteins are co-localized within the nucleus. TReP-132 reduces TdT activity to 2.5% of its maximum value in the in vitro assay system using double-stranded DNA with a 3' protrusion as a primer. These findings suggest that TdT synthesizes N region under a negative control of TReP-132 during V(D)J recombination.

Switching of NR5A proteins associated with the inhibin alpha-subunit gene promoter after activation of the gene in granulosa cells

The inhibin alpha-subunit gene is transcriptionally activated by FSH in ovarian granulosa cells during follicular growth. We have investigated the roles of the NR5A family nuclear receptors steroidogenic factor 1 (SF-1) and liver receptor homolog 1 (LRH-1) in transcriptional activation of the inhibin alpha-subunit gene. Transfection assays using an inhibin alpha-subunit promoter reporter in GRMO2 granulosa cells show that LRH-1 and SF-1 act similarly to increase promoter activity, and that the activity of both transcription factors is augmented by the coactivators cAMP response element-binding protein-binding protein and steroid receptor coactivator 1. However, chromatin immunoprecipitation experiments illustrate differential dynamic association of LRH-1 and SF-1 with the alpha-subunit inhibin promoter in both primary cells and the GRMO2 granulosa cell line such that hormonal stimulation of transcription results in an apparent replacement of SF-1 with LRH-1. Transcriptional stimulation of the inhibin alpha-subunit gene is dependent on MAPK kinase activity, as is the dynamic association/disassociation of SF-1 and LRH-1 with the promoter. Inhibition of the phosphatidylinositol 3-kinase signaling pathway influences promoter occupancy and transcriptional activation by SF-1 but not LRH-1, suggesting a possible mechanistic basis for the distinct functions of these NR5A proteins in inhibin alpha-subunit gene regulation.

Schistosoma mansoni CBP/p300 has a conserved domain structure and interacts functionally with the nuclear receptor SmFtz-F1

Metazoan species diversification in general and the adaptation of parasites to their life-style in particular are due, not only to the evolution of different structural or metabolic proteins, but also to changes in the expression patterns of the corresponding genes. In order to explore the conservation/divergence of transcriptional regulation in the platyhelminth parasite Schistosoma mansoni, we are studying the structures and functions of transcriptional mediators. CREB-binding protein (CBP) and p300 are closely related transcriptional coactivators that possess histone acetyltransferase (HAT) activity that can modify chromatin to an active relaxed state. They are also thought to link transcription factors to the basic transcriptional machinery and to act as integrators for different regulatory pathways. Here we describe the cloning and functional characterization of S. mansoni CBP. SmCBP1 comprises 2093 amino acids and displays a conserved modular domain structure. The HAT domain was shown to acetylate histones with a marked activity toward H4. Functional studies showed that SmCBP1 could interact physically with the nuclear receptor SmFtz-F1 and also potentiated its transcriptional activity in the CV-1 cell line. Screening of the EST and genomic sequence databases with the SmCBP1 sequence allowed us to characterize a second CBP gene in S. mansoni. SmCBP2 shows a high degree of sequence identity to SmCBP1, particularly in the HAT domain. Phylogenetic studies show that these peptides are more closely related to each other than to either mammalian CBP or p300, suggesting that they derive from a platyhelminth-specific duplication event. Both genes are expressed at all life-cycle stages, but differences in their relative expression and structural variations suggest that they play distinct roles in schistosome gene regulation.

Promoter Activity and Chromosomal Location of the Rana rugosa P450 Aromatase (CYP19) Gene

Sex is determined genetically in amphibians, but is reversed occasionally by steroid hormones. The phenotypic sex of some amphibian species can be reversed from male to female by estrogens. Estrogens, which are synthesized from testosterone irreversibly by the enzyme P450 aromatase (CYP19), are essential for ovarian development in vertebrates. CYP19 expression is reportedly regulated by steroidogenic factor-1 (SF-1), also designated as Ad4BP, in fish and mammals. However, it is unknown if this is also the case in amphibians. Thus, to elucidate the role of SF-1 in CYP19 gene expression in the gonad of amphibians, it is necessary to isolate and characterize the promoter region of the CYP19 gene of amphibians. For this purpose, we first cloned the promoter region of CYP19 from genomic DNA fragments of the frog Rana rugosa. As a result, a potential binding site of SF-1 was found in the region. When a luciferase promoter assay in HEK 293 cells was carried out to examine the ability of SF-1 as a transcriptional regulator, we found that R. rugosa SF-1 stimulated the expression of the CYP19 gene of the tilapia Oreochromis niloticus, but not that of the frogs R. rugosa and Xenopus laevis. RT-PCR analysis revealed that CYP19 mRNA was expressed at a higher level in the indifferent gonads of females than in those of males. This was also true to SF-1 mRNA In addition, FISH analysis showed that the CYP19 gene was located on chromosome 3 of R. rugosa. Taken together, our data suggest that CYP19, an autosomal gene, is expressed in the undifferentiated gonads to an extent greater in females than in males, but its expression probably is not regulated by SF-1 alone. Another factor(s) may be required if SF-1 promotes the expression of the CYP19 gene in R. rugosa as it does in fish and mammals.

SF-1 (nuclear receptor 5A1) activity is activated by cyclic AMP via p300-mediated recruitment to active foci, acetylation, and increased DNA binding

Steroidogenic factor 1 (SF-1) is a nuclear receptor essential for steroidogenic gene expression, but how its activity is regulated is unclear. Here we demonstrate that p300 plays an important role in regulating SF-1 function. SF-1 was acetylated in vitro and in vivo by p300 at the KQQKK motif in the Ftz-F1 (Fushi-tarazu factor 1) box adjacent to its DNA-binding domain. Mutation of the KQQKK motif reduced the DNA-binding activity and p300-dependent activation of SF-1. When stimulated with cyclic AMP (cAMP), adrenocortical Y1 cells expressed more p300, leading to additional SF-1 association with p300 and increased SF-1 acetylation and DNA binding. It also increased SF-1 colocalization with p300 in nuclear foci. Collectively, these results indicate that SF-1 transcriptional activity is regulated by p300 in response to the cAMP signaling pathway by way of increased acetylation, DNA binding, and recruitment to nuclear foci.

TReP-132 controls cell proliferation by regulating the expression of the cyclin-dependent kinase inhibitors p21WAF1/Cip1 and p27Kip1

The transcriptional regulating protein of 132 kDa (TReP-132) has been identified in steroidogenic tissues, where it acts as a coactivator of steroidogenic factor 1 (SF-1). We show here that TReP-132 plays a role in the control of cell proliferation. In human HeLa cells, TReP-132 knockdown by using small interfering RNA resulted in increased G(1)-->S cell cycle progression. The growth-inhibitory effects of TReP-132 was further shown to be mediated by induction of G(1) cyclin-dependent kinase inhibitors p21(WAF1) (p21) and p27(KIP1) (p27) expression levels. As a consequence, G(1) cyclin/cyclin-dependent kinase activities and pRB phosphorylation were markedly reduced, and cell cycle progression was blocked in the G(1) phase. The stimulatory effect of TReP-132 on p21 and p27 gene transcription involved interaction of TReP-132 with the transcription factor Sp1 at proximal Sp1-binding sites in their promoters. Moreover, in different breast tumor cell lines, endogenous TReP-132 expression was positively related with a lower proliferation rate. In addition, TReP-132 knockdown resulted in enhanced cell proliferation and lowered p21 and p27 mRNA levels in the steroid-responsive and nonresponsive T-47D and MDA-MB-231 cell lines, respectively. Finally, a statistic profiling of human breast tumor samples highlighted that expression of TReP-132 is correlated with p21 and p27 levels and is associated with lower tumor incidence and aggressiveness. Together, these results identify TReP-132 as a basal cell cycle regulatory protein acting, at least in part, by interacting with Sp1 to activate the p21 and p27 gene promoters.

EID3 is a novel EID family member and an inhibitor of CBP-dependent co-activation

EID1 (E1A-like inhibitor of differentiation 1) functions as an inhibitor of nuclear receptor-dependent gene transcription by directly binding to co-regulators. Alternative targets include the co-repressor small heterodimer partner (SHP, NR0B2) and the co-activators CBP/p300, indicating that EID1 utilizes different inhibitory strategies. Recently, EID2 was characterized as an inhibitor of muscle differentiation and as an antagonist of both CBP/p300 and HDACs. Here, we describe a third family member designated EID3 that is highly expressed in testis and shows homology to a region of EID1 implicated in binding to CBP/p300. We demonstrate that EID3 acts as a potent inhibitor of nuclear receptor transcriptional activity by a mechanism that is independent of direct interactions with nuclear receptors, including SHP. Furthermore, EID3 directly binds to and blocks the SRC-1 interacting domain of CBP, which has been implicated to act as the interaction surface for nuclear receptor co-activators. Consistent with this idea, EID3 prevents recruitment of CBP to a natural nuclear receptor-regulated promoter. Our study suggests that EID-family members EID3 and EID1 act as inhibitors of CBP/p300-dependent transcription in a tissue-specific manner.

Molecular biology of the 3beta-hydroxysteroid dehydrogenase/delta5-delta4 isomerase gene family

The 3beta-hydroxysteroid dehydrogenase/Delta(5)-Delta(4) isomerase (3beta-HSD) isoenzymes are responsible for the oxidation and isomerization of Delta(5)-3beta-hydroxysteroid precursors into Delta(4)-ketosteroids, thus catalyzing an essential step in the formation of all classes of active steroid hormones. In humans, expression of the type I isoenzyme accounts for the 3beta-HSD activity found in placenta and peripheral tissues, whereas the type II 3beta-HSD isoenzyme is predominantly expressed in the adrenal gland, ovary, and testis, and its deficiency is responsible for a rare form of congenital adrenal hyperplasia. Phylogeny analyses of the 3beta-HSD gene family strongly suggest that the need for different 3beta-HSD genes occurred very late in mammals, with subsequent evolution in a similar manner in other lineages. Therefore, to a large extent, the 3beta-HSD gene family should have evolved to facilitate differential patterns of tissue- and cell-specific expression and regulation involving multiple signal transduction pathways, which are activated by several growth factors, steroids, and cytokines. Recent studies indicate that HSD3B2 gene regulation involves the orphan nuclear receptors steroidogenic factor-1 and dosage-sensitive sex reversal adrenal hypoplasia congenita critical region on the X chromosome gene 1 (DAX-1). Other findings suggest a potential regulatory role for STAT5 and STAT6 in transcriptional activation of HSD3B2 promoter. It was shown that epidermal growth factor (EGF) requires intact STAT5; on the other hand IL-4 induces HSD3B1 gene expression, along with IL-13, through STAT 6 activation. However, evidence suggests that multiple signal transduction pathways are involved in IL-4 mediated HSD3B1 gene expression. Indeed, a better understanding of the transcriptional factors responsible for the fine control of 3beta-HSD gene expression may provide insight into mechanisms involved in the functional cooperation between STATs and nuclear receptors as well as their potential interaction with other signaling transduction pathways such as GATA proteins. Finally, the elucidation of the molecular basis of 3beta-HSD deficiency has highlighted the fact that mutations in the HSD3B2 gene can result in a wide spectrum of molecular repercussions, which are associated with the different phenotypic manifestations of classical 3beta-HSD deficiency and also provide valuable information concerning the structure-function relationships of the 3beta-HSD superfamily. Furthermore, several recent studies using type I and type II purified enzymes have elegantly further characterized structure-function relationships responsible for kinetic differences and coenzyme specificity.