An NF-Y binding site is important for basal, but not gonadotropin-releasing hormone-stimulated, expression of the luteinizing hormone beta subunit gene

Regulated synthesis of luteinizing hormone (LH) re quires coordinated trans criptional control of the alpha and LH beta subunits in pituitary gonadotro pes. Several cis-acting elements and trans-acting factors have been defined for control of the LH beta promoter through heterologous cell culture mode ls. In this report, we describe the identification of bipartite NF-Y (CBF/C P1) binding sites within the proximal bovine LH beta promoter. When multime rized, one of these sites activates the heterologous, minimal HSV thymidine kinase promoter in the gonadotrope-derived cell line alpha T3-1. The funct ional role of the promoter-distal site in regulating the full-length bovine LH beta promoter was assessed in vivo using transgenic mice harboring a mu tant promoter linked to the chloramphenicol acetyltransferase reporter gene . While this element is important for conferring high level activity of the LH beta promoter in pituitary, it does not appear to be essential for medi ating gonadotropin-releasing hormone (GnRH) regulation. This is the first c haracterization of a cia-acting element within this GnRH-dependent promoter that is restricted to regulating basal expression and not GnRH-induced act ivity.