Evidence for autocrine inhibition of gonadotropin-releasing hormone (GnRH) gene transcription by GnRH in hypothalamic GT1-1 neuronal cells.
To examine whether an ultrashort feedback mechanism of gonadotropin-releasing hormone (GnRH) operates at the level of gene transcription, we studied the effects of GnRH analogs on GnRH promoter activity and GnRH mRNA level in hypothalamic GT1-1 neuronal cells. Treatment of GT1-1 cells with buserelin, a GnRH agonist, or native GnRH for 24 h significantly decreased GnRH promoter activity and its mRNA level, whereas that with GnRH antagonists, antide or [D-Phe2,D-Ala6]-GnRH, showed no effect. The inhibitory effects of buserelin on GnRH gene transcription and GnRH mRNA level were dose-related, and a significant inhibition was observed in cells treated with buserelin at concentrations higher than 0.1 microM. Time-course experiments showed that significant decreases in GnRH promoter-driven luciferase activity and GnRH mRNA level were observed within 12 h and sustained up to 48 h. Moreover, treatment with GnRH agonist for 12 h significantly decreased the transcription rate of the mouse GnRH gene, as revealed by nuclear run-on transcription assay. The promoter analysis with the 5'-deletional constructs demonstrated that cis-acting elements important for GnRH autoregulation by GnRH agonist reside within -854 bp upstream from the transcription start site. These data clearly demonstrate that GnRH can exert autocrine regulation at the level of GnRH gene transcription.
Cho
S
S
Department of Molecular Biology and Research Center for Cell Differentiation, Seoul National University, South Korea.
Han
J
J
Sun
W
W
Choi
D
D
Kwon
H B
HB
Jarry
H
H
Wuttke
W
W
Kim
K
K
D000818:Animals; D019898:Autocrine Communication; D002064:Buserelin / Q000494:pharmacology; D002452:Cell Count; D002460:Cell Line; D005246:Feedback; D007987:Gonadotropin-Releasing Hormone / Q000235:genetics*; D007031:Hypothalamus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D014158:Transcription, Genetic
D007987:Gonadotropin-Releasing Hormone; D002064:Buserelin