A 6-kb promoter fragment mimics in transgenic mice the prostate-specific and androgen-regulated expression of the endogenous prostate-specific antigen gene in humans

Prostate-specific antigen (PSA) is a kallikrein-like serine protease, which is almost exclusively synthesized in the luminal epithelial cells of the human prostate. PSA expression is androgen regulated. Previously, we characterized in vitro the proximal promoter, and a strong enhancer region, approximately 4 kb upstream of the PSA gene. Both regions are needed for high, androgen-regulated activity of the PSA promoter in LNCaP cells. The goal of the present study is the in vivo characterization of the PSA promoter. Three transgenic mouse lines carrying the Escherichia coli LacZ gene, driven by the 632-bp proximal PSA promoter, and three lines with LacZ, driven by the 6-kb PSA promoter, were generated. Expression of the LacZ reporter gene was analyzed in a large series of tissues. Transgene expression could not be demonstrated in any of the transgenic animals carrying the proximal PSA promoter. All three lines carrying the 6-kb PSA promoter showed lateral prostate-specific beta-galactosidase activity. Transgene expression was undetectable until 8 weeks after birth. Upon castration, beta-galactosidase activity rapidly declined. It could be restored by subsequent androgen administration. A search for mouse PSA-related kallikrein genes expressed in the prostate led to the identification of mGK22, which was previously demonstrated to be expressed in the submandibular salivary gland. Therefore, the 6-kb PSA-LacZ transgene followed the expression pattern of the PSA gene in humans, which is almost completely prostate-specific, rather than that of mGK22 in mice. In conclusion, the 6-kb promoter fragment appears to contain most, if not all, information for androgen regulation and prostate specificity of the PSA gene

Regulation of the zebrafish goosecoid promoter by mesoderm inducing factors and Xwnt1

Goosecoid is a homeobox gene that is expressed as an immediate early response to mesoderm induction by activin. We have investigated the induction of the zebrafish goosecoid promoter by the mesoderm inducing factors activin and basic fibroblast growth factor (bFGF) in dissociated zebrafish blastula cells, as well as by different wnts in intact embryos. Activin induces promoter activity, while bFGF shows a cooperative effect with activin. We have identified two enhancer elements that are functional in the induction of the goosecoid promoter. A distal element confers activin responsiveness to a heterologous promoter in the absence of de novo protein synthesis, whereas a proximal element responds only to a combination of activin and bFGE Deletion experiments show that both elements are important for full induction by activin. Nuclear proteins that bind to these elements are expressed in blastula embryos, and competition experiments show that an octamer site in the activin responsive distal element is specifically bound, suggesting a role for an octamer binding factor in the regulation of goosecoid expression by activin. Experiments in intact embryos reveal that the proximal element contains sequences that respond to Xwnt1, but not to Xwnt5c. Furthermore, we show that the distal element is active in a confined dorsal domain in embryos and responds to overexpression of activin in vivo, as well as to dorsalization by lithium. The distal element is to our knowledge the first enhancer element identified that mediates the induction of a mesodermal gene by activin