Summary Androgen receptor (AR) functions as a transcriptional factor for the development and progression of prostate cancer. Resveratrol is known to inhibit the function of AR and to repress AR expression at the transcriptional level. This study focuses on the effects of resveratrol on the AR function and the post-translational AR level. Resveratrol repressed the transcriptional activities of a mutant AR lacking the ligand-binding domain, a constitutive active form of AR, and wild-type AR in a concentration-dependent manner in human prostate cancer PC-3 cells, indicating that resveratrol does not inhibit the transcriptional activity of AR through binding to the ligand-binding domain of AR. Furthermore, the half-life of AR protein was approximately 4 h in resveratrol-treated AR-positive prostate cancer LNCaP cells, compared to approximately 13 h in control cells, as determined by cycloheximide chase. These results indicate that resveratrol down-regulates AR protein through a posttranslational mechanism and suggest that the inhibitory effect of resveratrol on AR function is partly attributable to a decrease in the post-translational AR level.

No abstract

No abstract

Androgenic compounds induce an interaction between the NH 2 -and COOH-terminal regions (N-C interaction) of androgen receptor (AR). We describe a rapid yeast bioassay for androgenic and anti-androgenic compounds based on androgen-dependent -catenin-enhanced N-C interaction. The bioassay was also effective at detecting compounds that inhibit the N-C interaction in ways that do not involve binding to the ligand-binding domain.Key words: androgen receptor (AR); bioassay; N-C interaction; -catenin; yeast two-hybridAndrogens such as testosterone and its metabolite dihydrotestosterone (DHT) act through binding to the androgen receptor (AR) not only in physiological processes such as male sexual differentiation and the development of bone, muscle, and reproductive tissues, but also in pathophysiological processes such as prostate tumor growth. 1) Androgen-bound AR interacts with androgen response elements (AREs) in the promoters of target genes and functions as a transcriptional factor. The recruitment of coactivators to AR enhances AR transactivation. The AR possesses three functional domains: an NH 2 -terminal domain (NTD), a central DNA-binding domain, and a COOH-terminal ligandbinding domain (LBD).2) The binding of ligands to the LBD triggers intramolecular or intermolecular interaction between the NH 2 -and COOH-terminal regions (N-C interaction) of the AR. The N-C interaction is enhanced by certain coactivators including -catenin, 3) ARA24/Ran, 4) and p160 family proteins such as steroid receptor coactivator-1 (SRC-1) 5) and transcriptional intermediate factor-2 (TIF-2), 3) and is required for proper and maximal AR transactivation.AR agonists and antagonists are expected to be effective for the prevention of male osteoporosis and for the inhibition of prostate cancer growth respectively. 6,7) Accordingly, several bioassays for the detection of androgenic and anti-androgenic compounds have been developed using both mammalian and yeast cells. Mammalian-based assays have higher sensitivity for detection of androgenic activity than yeast-based assays, but yeast-based assays are simpler, more rapid, and cheaper than mammalian-based assays. Furthermore, there is no contamination of steroids in yeast-based assays, whereas in mammalian-based assays, steroidal compounds must be removed from the media because fetal bovine serum including various steroids is added to them.Previous yeast bioassays based on interaction between a coactivator and the LBD of AR require grinding of cells and the addition of substrate for the reporter gene product (usually -galactosidase), which is timeconsuming and costly. To avoid these problems, a new yeast bioassay using a green fluorescent protein (GFP) as a reporter gene has been developed. However, the 50% effective concentration (EC 50 ) values of various steroids, including testosterone and DHT, are higher in bioassays using GFP than in bioassays usinggalactosidase. Here, we describe a new yeast bioassay based on the androgen-dependent N-C interaction, which is enhanced by -catenin and mo...