Androgen induction of a human prostate-specific kallikrein, hKLK2: characterization of an androgen response element in the 5' promoter region of the gene.
The human prostate-specific kallikreins, human glandular kallikrein-1 (hKLK2) and prostate-specific antigen (hKLK3), have been shown to be regulated by androgens. To determine whether the androgen induction of these genes is transcriptionally regulated via an androgen response element, an hKLK2 promoter DNA fragment was linked to a promoterless chloramphenicol acetyltransferase (CAT) reporter gene and cotransfected with an androgen receptor expression vector in an androgen receptor-less human prostate cell line, PC-3. Dose response and steroid specificity experiments showed that the hKLK2 promoter confers androgen receptor-mediated gene induction in a ligand-specific manner. Moreover, 5' deletion constructs of the hKLK2 promoter DNA and internal deletion constructs devoid of the 5' half-site of the putative androgen responsive element (ARE) were used to show that the putative ARE is indeed acting as a functional ARE in prostate cells. In addition, multiple AREs from both hKLK2 and hKLK3 were able to reconstitute androgenic induction, further strengthening the argument that the AREs are functional. Although previous studies have shown that hKLK3 mRNA is expressed at a higher level than that of hKLK2, our results suggest that the hKLK2 ARE may have higher androgenic inducibility than the hKLK3 ARE. These results suggest that other cis-acting elements may be involved in coordinating in vivo androgenic induction of hKLK2 and hKLK3 genes.