A Novel Role for the Forkhead Transcription Factor FOXL2 in Activin A-Regulated Follicle-Stimulating Hormone β Subunit Transcription

• Published in: Molecular endocrinology (Baltimore, Md.) Md.), 2009-07, Vol.23 (7), p.1001-1013
• Main Authors: Lamba, Pankaj, Fortin, Jérôme, Tran, Stella, Wang, Ying, Bernard, Daniel J
• Format: Article
• Language: English
• Subjects: Activins - pharmacology; Animals; Base Sequence; Cells, Cultured; CHO Cells; Cricetinae; Cricetulus; Follicle Stimulating Hormone, beta Subunit - genetics; Forkhead Box Protein L2; Forkhead Transcription Factors - physiology; Gene Expression Regulation - drug effects; Gene Expression Regulation - genetics; Humans; Mice; Molecular Sequence Data; Promoter Regions, Genetic - drug effects; Sequence Homology, Nucleic Acid; Swine - genetics; Transcription, Genetic - drug effects; Transcription, Genetic - genetics
• ISSN: 0888-8809; 1944-9917
• DOI: 10.1210/me.2008-0324

Selective synthesis and release of FSH from pituitary gonadotropes is regulated by activins. Activins directly stimulate murine FSHβ (Fshb) subunit gene transcription through a consensus 8-bp Sma- and Mad-related protein-binding element (SBE) in the proximal promoter. In contrast, the human FSHB promoter is relatively insensitive to the direct effects of activins and lacks this SBE. The proximal porcine Fshb promoter, which is highly conserved with human, similarly lacks the 8-bp SBE, but is nonetheless highly sensitive to activins. We used a comparative approach to determine mechanisms mediating differential activin induction of human, porcine, and murine Fshb/FSHB promoters. We mapped an activin response element in the proximal porcine promoter and identified interspecies variation in a single base pair in close proximity that conferred strong binding of the forkhead transcription factor FOXL2 to the porcine, but not human or murine, promoters. Introduction of the human base pair into the porcine promoter abolished FOXL2 binding and activin A induction. FOXL2 conferred activin A induction to the porcine promoter in heterologous cells, whereas knockdown of the endogenous protein in gonadotropes inhibited the activin A response. The murine Fshb promoter lacks the high-affinity FOXL2-binding site, but its activin induction is FOXL2 sensitive. We identified a more proximal FOXL2-binding element in the murine promoter, which is conserved across species. Mutation of this site attenuated activin A induction of both the porcine and murine promoters. Collectively, the data indicate a novel role for FOXL2 in activin A-regulated Fshb transcription. The forkhead transcription factor FOXL2 binds to distinct and conserved elements in the proximal FSHbeta subunit gene promoter, mediating activin induction in species-specific fashion.