title: Frequency-dependent regulation of follicle-stimulating hormone beta by pulsatile gonadotropin-releasing hormone is mediated by functional antagonism of bZIP transcription factors.
abstract: Oscillatory synthesis and secretion of the gonadotropins, follicle-stimulating hormone (FSH) and luteinizing hormone (LH), under the control of pulsatile hypothalamic gonadotropin-releasing hormone (GnRH), is essential for normal reproductive development and fertility. The molecular mechanisms by which various patterns of pulsatile GnRH regulate gonadotrope responsiveness remain poorly understood. In contrast to the alpha and LH beta subunit genes, FSH beta subunit transcription is preferentially stimulated at low rather than high frequencies of pulsatile GnRH. In this study, mutation of a cyclic AMP response element (CRE) within the FSH beta promoter resulted in the loss of preferential GnRH stimulation at low pulse frequencies. We hypothesized that high GnRH pulse frequencies might stimulate a transcriptional repressor(s) to attenuate the action of CRE binding protein (CREB) and show that inducible cAMP early repressor (ICER) fulfills such a role. ICER was not detected under basal conditions, but pulsatile GnRH stimulated ICER to a greater extent at high than at low pulse frequencies. ICER binds to the FSH beta CRE site to reduce CREB occupation and abrogates both maximal GnRH stimulation and GnRH pulse frequency-dependent effects on FSH beta transcription. These data suggest that ICER production antagonizes the stimulatory action of CREB to attenuate FSH beta transcription at high GnRH pulse frequencies, thereby playing a critical role in regulating cyclic reproductive function.
authors.affiliation: Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women's Hospital, 221 Longwood Ave., Boston, MA 02115, USA.
authors.forename: Nick A
authors.initials: NA
authors.lastname: Ciccone
authors.forename: Shuyun
authors.initials: S
authors.lastname: Xu
authors.forename: Charlemagne T
authors.initials: CT
authors.lastname: Lacza
authors.forename: Rona S
authors.initials: RS
authors.lastname: Carroll
authors.forename: Ursula B
authors.initials: UB
authors.lastname: Kaiser
mesh_terms: D000249:Adenosine Monophosphate / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D051786:Cyclic AMP Response Element Modulator / Q000037:antagonists & inhibitors / Q000378:metabolism*; D037201:Follicle Stimulating Hormone, beta Subunit / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D051379:Mice; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D034622:RNA Interference; D020218:Response Elements; D014158:Transcription, Genetic
chemical_list: C497411:Crem protein, mouse; D037201:Follicle Stimulating Hormone, beta Subunit; D051786:Cyclic AMP Response Element Modulator; D007987:Gonadotropin-Releasing Hormone; D000249:Adenosine Monophosphate