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

Abstract

Pin1 is a peptidyl-prolyl cis-trans isomerase which catalyzes the isomerization of phosphorylated Ser/Thr-Pro peptide bonds. Pin1 knockout mice have marked abnormalities in their reproductive development and function. However, the molecular mechanisms underlying their reproductive defects are poorly understood. Herein, we demonstrate that Pin1 is required for both basal and GnRH-induced gonadotropin ␤-subunit gene transcription, through interactions with the transcription factors SF-1, Pitx1, and Egr-1. Pin1 activates transcription of the gonadotropin ␤-subunit genes synergistically with these transcription factors, either by modulating their stability or by increasing their protein-protein interactions. Notably, we provide evidence that Pin1 is required for the Ser203 phosphorylation-dependent ubiquitination of SF-1, which facilitates SF-1-Pitx1 interactions and therefore results in an enhancement of SF-1 transcriptional activity. Furthermore, we demonstrate that in gonadotrope cells, sufficient levels of activated Pin1 are maintained through transcriptional and posttranslational regulation by GnRH-induced signaling cascades. Our results suggest that Pin1 functions as a novel player in GnRH-induced signal pathways and is involved in gonadotropin ␤-subunit gene transcription by modulating the activity of various specific transcription factors.

RNA transcribed from a distal enhancer is required for activating the chromatin at the promoter of the gonadotropin α-subunit gene

“…Murine gonadotropederived αT3-1 cells were cultured and transfected as described (43), and some were treated with GnRH (100 nM) or forskolin (10 μM; Sigma). HA-and FLAGPitx1 expression constructs have been reported previously (44). Pitx1 knockdown for 48 h used shRNA cloned into pSUPER-basic, and stable knockdown was achieved via pSR-GFP/neo plasmid (both from OligoEngine) expressing the shRNA (Table S1); clones were selected using G418 as in ref.…”

Prolyl isomerase Pin1 in cancer

“…In addition, Pin1 activates SF-1, Pitx1 and Egr-1 transcription factors, either by modulating their stability or by increasing their protein-protein interactions. For instance, Pin1 is required for the S203 phosphorylation-dependent ubiquitylation of SF-1, which facilitates the interaction between SF-1 and Pitx1, and therefore enhances SF-1 transcriptional activity [91]. Thus, Pin1 regulates a broad range of transcription factors in central pathways that are important for tumor development.…”

Phosphorylation stabilizes Nanog by promoting its interaction with Pin1

“…By isomerizing the pS/T-Pro bonds, Pin1 has been shown to induce conformational change in proteins, including cyclin D1, p73 and p53, thereby having profound impacts on their phosphorylation state, catalytic activity, protein-protein interactions, and turnover (16)(17)(18)(19). In particular, recent results indicate that such Pin1 activity is correlated with a change in target protein stability through a ubiquitin-mediated mechanism (20)(21)(22)(23)(24)(25). These data indicate that Pin1 dependent conformational changes are a unique signaling mechanism pivotal in regulating many cellular functions.…”