The clusterin gene, also known as the sulfated glycoprotein (SGP-2) gene, is expressed and regulated in a tissue-specific manner in the testis, male accessory sex organs, and many other tissues. The expression of the clusterin gene was shown to be negatively regulated by androgens in rat prostate and by cAMP in testicular cells. Although the ability of cAMP to stimulate gene expression has been studied in many systems; little is known about the negative effect of cAMP in several Leydig tumor cell lines can be used as a unique model system to investigate the possible mechanisms involved in the cell-specific inhibition of gene expression by cAMP. In this project, we propose to study the structure of the clusterin gene and the negative hormonal control of this expression. Our first specific aim is to characterize the structure of the rat clusterin gene, in particular, the 5-flanking region of the gene. The second specific aim is to determine the DNA elements and protein factors that are required for the cell- specific basal expression of the clusterin gene in testicular cells and in the male accessory sex organs. We will examine whether a negative androgen-responsive element is responsible for the suppression of this gene by androgens in ventral prostate. Our third specific aim is to investigate the mechanisms (transcriptional activity and mRNA stability) involved in the negative cAMP-responsive elements and the protein factors that are responsible for the inhibitory effect of cAMP in Leydig tumor cell lines and in primary cultures of Leydig and Sertoli cells. Finally, we will investigate whether gonadotropins, acting through cAMP, and androgens also exert inhibitory effects in vivo on clusterin mRNA and protein levels in Leydig cells of rat testis. Clusterin is believed to exert a protective function on cells of the male reproductive tract and on germ cells. The information that will be obtained from this project on the hormonal regulation of this gene will facilitate our understanding of the role that clusterin may play in the male reproductive function.