DNA-SEQUENCES REQUIRED FOR EXPRESSION OF THE LH-BETA PROMOTER IN PRIMARY CULTURES OF RAT PITUITARY-CELLS

To begin analysis of the DNA sequences necessary for luteinizing hormone (LH) gene transcription, fusion genes containing the 5′ flanking region of the rat LHβ or the human α-subunit gene linked to luciferase were transfected into primary cultures of rat pituitary cells. The LHβ-luciferase construct was expressed in the primary cultures at a level 50 times greater than a promoterless luciferase control plasmid. Little or no expression of the LHβ-luciferase construct was detected following transfection of MCF-7, JAR or GH3 tumor cell lines. Treatment of transfected cells with gonadotropin-releasing hormone resulted in a modest induction of LHβ-luciferase activity. Considerably higher levels of LHβ-luciferase activity were obtained with cultures from ovariectomized rats than were obtained with cultures from intact female rats. Analysis of 5′ deletions of the LHβ-luciferase construct demonstrated that activity was well maintained even after substantial deletions. The shortest construct, which contained 75 base pairs of 5′ flanking sequence had 38% of the activity of the longest which contained 1.7 kilobase pairs of flanking sequence. These findings demonstrate that transfection of primary cultures of rat pituitary cells may provide a useful system for analysis of the cis-acting sequences and trans-acting factors required for LH gene expression. © 1990.