The equine luteinizing hormone beta-subunit promoter contains two functional steroidogenic factor-1 response elements

Area of Science:

• Endocrinology
• Molecular Biology
• Genetics

Background:

• Basal expression requirements for the luteinizing hormone (LH) beta-subunit promoter in pituitary gonadotropes are not fully understood.
• The equine LH beta-subunit promoter serves as a model to decipher the regulatory code for gonadotrope expression.

Purpose of the Study:

• To identify the regulatory elements and combinatorial code responsible for basal expression of the equine LH beta-subunit promoter in pituitary gonadotropes.

Main Methods:

• 5'-deletion mutagenesis and block replacement mutagenesis of the equine LH beta-subunit promoter.
• Electrophoretic mobility shift assays (EMSAs) to confirm transcription factor binding.
• Reporter gene assays in alphaT3-1 and LbetaT2 cell lines.
• Cotransfection studies with steroidogenic factor-1 (SF-1) expression vectors.

Main Results:

• A critical region between -185 and -100 of the equine LH beta-subunit promoter was identified for basal activity.
• Two SF-1 binding sites were confirmed, with mutations affecting promoter activity differentially in alphaT3-1 and LbetaT2 cells.
• Two important DNA response elements were identified: a distal 31-bp segment (-181 to -150) and an element at -119 to -106.
• SF-1 cotransfection induced promoter activity, which was dependent on the integrity of the SF-1 binding sites.

Conclusions:

• The study elucidates key regulatory regions and SF-1 binding sites within the equine LH beta-subunit promoter.
• These elements likely contribute to a combinatorial code that directs promoter expression specifically to pituitary gonadotropes.
• Further research into this combinatorial code can advance understanding of gonadotropin gene regulation.