MULTIPLE PROMOTER ELEMENTS CONTRIBUTE TO ACTIVITY OF THE FOLLICLE-STIMULATING-HORMONE RECEPTOR (FSHR) GENE IN TESTICULAR SERTOLI CELLS

The FSH receptor (FSHR) is expressed only in granulosa cells of the ov ary and Sertoli cells of the testis, This highly specific pattern of g ene expression asserts that transcriptional events unique to these two cell types are responsible for activation of the FSHR gene. We have c haracterized the promoter elements required for activity of the rat FS HR gene in a Sertoli cell line MSC-1, primary cultures of rat Sertoli cells, and two non-Sertoli cell lines. Transient transfection analysis of deletion and block replacement mutants identified several elements , both 5' and 3' to the transcriptional start sites, that are essentia l for full promoter activity in Sertoli cells. These studies confirmed the use of an important E box element (CACGTG), which had the single greatest impact on promoter function. Bases within the core CACGTG of the E box, as well as flanking sequences, were shown to be essential f or its function. Electrophoretic mobility shift assays identified both upstream stimulatory factor 1 (USF1) and USF2 as primary components o f the complexes binding the E box. Sequence requirements for USF bindi ng in vitro modestly diverged from the sequence requirements for in vi vo function of the element. Comparison of the E box binding proteins i n different cell types revealed that similar proteins bind the E box i n Sertoli and non-Sertoli cell lines. Extracts from primary cultures o f rat and mouse Sertoli cells have a second E box-binding complex that cross-reacts with USF antibodies that is not present in the cell line s.