The human alpha subunit glycoprotein hormone gene utilizes a unique CCAAT binding factor

Area of Science:

• Molecular Biology
• Genetics
• Endocrinology

Background:

• Placenta-specific expression of the glycoprotein hormone alpha subunit gene is regulated by cis-acting elements like the upstream regulatory element (URE) and cAMP-response elements (CREs).
• Understanding the complete regulatory network is essential for deciphering placental gene expression.

Purpose of the Study:

• To identify additional cis-acting elements and trans-acting factors involved in regulating the human alpha subunit gene promoter activity.
• To characterize a novel CCAAT-binding factor in the proximal promoter-regulatory region.

Main Methods:

• Block replacement mutagenesis of the human alpha subunit gene promoter region.
• Transient expression assays in choriocarcinoma cells.
• Gel mobility shift assays, methylation interference analyses, and UV cross-linking.

Main Results:

• Identification of several closely spaced transcriptional control elements beyond URE and CREs.
• Discovery of a novel factor, alpha subunit CCAAT-binding factor (alpha CBF), binding to a CCAAT box.
• Alpha CBF is present in various cell types and distinct from known CCAAT-binding factors.

Conclusions:

• The novel alpha CBF is a key regulator of the alpha subunit gene promoter.
• Interaction of alpha CBF with factors binding to URE and CREs is likely essential for maximal promoter activity in placental cells.
• This finding contributes to understanding the complex transcriptional regulation of glycoprotein hormones in placental development.