title: Functional cooperation between multiple regulatory elements in the untranslated exon 1 stimulates the basal transcription of the human GnRH-II gene.
abstract: The wide distribution of GnRH-II and conservation of its structure over all vertebrate classes suggest that the neuropeptide possesses vital biological functions. Although recent studies have shown that the expression of the human GnRH-II gene is regulated by cAMP and estrogen, the molecular mechanisms governing its basal transcription remain poorly understood. Using the neuronal TE-671 and placental JEG-3 cells, we showed that the minimal human GnRH-II promoter was located between nucleotide -1124 and -750 (relative to the translation start codon) and that the untranslated exon 1 was important to produce full promoter activity. Two putative E-box binding sites and one Ets-like element were identified within the first exon, and mutational analysis demonstrated that these cis-acting elements functioned cooperatively to stimulate the human GnRH-II gene transcription. EMSAs, UV cross-linking, and Southwestern blot analyses indicated that the basic helix-loop-helix transcription factor AP-4 bound specifically to the two E-box binding sites, whereas an unidentified protein bound to the Ets-like element. The functional importance of AP-4 in controlling human GnRH-II gene transcription was demonstrated by overexpression of sense and antisense full-length AP-4 cDNAs. Taken together, our present data demonstrate a novel mechanism in stimulating basal human GnRH-II gene transcription mediated by cooperative actions of multiple regulatory elements within the untranslated first exon of the gene.
authors.affiliation: Department of Obstetrics and Gynecology, University of British Columbia, Vancouver, Canada V6H 3V5.
authors.forename: Chi Keung
authors.initials: CK
authors.lastname: Cheng
authors.forename: Ruby L C
authors.initials: RL
authors.lastname: Hoo
authors.forename: Billy K C
authors.initials: BK
authors.lastname: Chow
authors.forename: Peter C K
authors.initials: PC
authors.lastname: Leung
mesh_terms: D001483:Base Sequence; D002460:Cell Line; D016373:DNA, Antisense; D018076:DNA, Complementary / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D024721:E-Box Elements; D005091:Exons; D015870:Gene Expression; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000235:genetics* / Q000378:metabolism; D018257:Helix-Loop-Helix Motifs; D006801:Humans; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012045:Regulatory Sequences, Nucleic Acid; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D024363:Transcription Initiation Site; D014158:Transcription, Genetic; D020506:Untranslated Regions
chemical_list: D016373:DNA, Antisense; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D014157:Transcription Factors; D020506:Untranslated Regions; C055473:enhancer-binding protein AP-4; D007987:Gonadotropin-Releasing Hormone; C047717:LHRH, His(5)-Trp(7)-Tyr(8)-