Functional cooperation between multiple regulatory elements in the untranslated exon 1 stimulates the basal transcription of the human GnRH-II gene.
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.
Cheng
Chi Keung
CK
Department of Obstetrics and Gynecology, University of British Columbia, Vancouver, Canada V6H 3V5.
Hoo
Ruby L C
RL
Chow
Billy K C
BK
Leung
Peter C K
PC
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
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)-