Phosphorylation of Steroidogenic Factor 1 Is Mediated by Cyclin-Dependent Kinase 7

Abstract

The nuclear receptor steroidogenic factor-1 (SF1) is critical for development and function of steroidogenic tissues. Posttranslational modifications are known to influence the transcriptional capacity of SF1, and it was previously demonstrated that serine 203 is phosphorylated. In this paper we report that serine 203 is phosphorylated by a cyclin-dependent kinase 7 (CDK7)-mediated process. As part of the CDK-activating kinase complex, CDK7 is a component of the basal transcription factor TFIIH, and phosphorylation of SF1 as well as SF1-dependent transcription was clearly reduced in cells carrying a mutation that renders the CDK-activating kinase complex unable to interact with the TFIIH core. Coimmunoprecipitation analyses revealed that SF1 and CDK7 reside in the same complex, and kinase assays demonstrated that immunoprecipitated CDK7 and purified TFIIH phosphorylate SF1 in vitro. The CDK inhibitor roscovitine blocked phosphorylation of SF1, and an inactive form of CDK7 repressed the phosphorylation level and the transactivation capacity of SF1. Structural studies have identified phosphoinositides as potential ligands for SF1. Interestingly, we found that mutations designed to block phospholipid binding dramatically decreased the level of SF1 phosphorylation. Together our results suggest a connection between ligand occupation and phosphorylation and association with the basic transcriptional machinery, indicating an intricate regulation of SF1 transactivation.

Pin1 Facilitates the Phosphorylation-Dependent Ubiquitination of SF-1 To Regulate Gonadotropin β-Subunit Gene Transcription

“…The ability of GnRH to increase SF-1 ubiquitination was shown recently (60), and our use of an ERK-specific inhibitor indicates that it likely stems from activation of ERK1/2; the MAPK cascade was shown previously to phosphorylate SF-1 both in vivo and in vitro (9,12,16). However, SF-1 is also reportedly phosphorylated by CDK7 and TFIIH (28). Activation of CDK7 relies on its Thr170 phosphorylation (13), which is present even without GnRH stimulation (unpublished data), indicating that CDK7 may be constitutively active in gonadotrope cells.…”

“…These results suggest that phosphorylation of SF-1 at S203 by GnRH-activated ERK2 contributes to SF-1 ubiquitination. SF-1 was reported to be constitutively phosphorylated under normal culture conditions (16), and CDK7, a component of the general transcription factor IIH, was shown to phosphorylate SF-1 on Ser203 (28). Therefore, we asked whether SF-1 ubiquitination is also affected by CDK7-mediated phosphorylation of SF-1.…”

“…Phosphorylation of SF-1 at Ser203, by ERK1/2 or CDK7, was shown to be required for maximal SF-1 target gene transactivation and recruitment of various cofactors (12,16,28). However, SF-1 is subject to additional posttranslational modifications which alter its activity, and it can be SUMOylated at two conserved lysines, Lys119 and Lys194, which are adjacent to the DNA-binding domain (DBD) and LBD, respectively.…”

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

“…SF1 plays an essential role in inducing the transcription of multiple steroidogenic genes, including cytochrome CYP17A1 in the adrenal cortex and gonads. The ability of SF1 to activate target genes is regulated by mechanisms including coregulatory proteins (60)(61)(62)(63), posttranslational modifi cation ( 27,28,(64)(65)(66)(67)(68), and ligand binding ( 25,(69)(70)(71)(72).…”

Adrenocortical development and cancer: focus on SF-1

“…SF-1 binds as a monomer to nuclear receptor half sites on DNA (Wilson et al 1993). Its transcriptional activity can be regulated by putative phospholipid ligands that bind inside its hydrophobic pocket (Krylova et al 2005, Li et al 2005, Wang et al 2005, and by post-translational modifications, namely phosphorylation by different kinases at Ser203 (Hammer et al 1999, Lewis et al 2008) and sumoylation, which may affect subnuclear localization of SF-1 and its DNA-binding activity (Chen et al 2004, Komatsu et al 2004, Lee et al 2005, Campbell et al 2008). …”