Identification and characterization of a novel factor that regulates quinone reductase gene transcriptional activity.

The regulation of the quinone reductase (QR) gene as well as other genes involved in detoxification is known to be mediated by an electrophile/antioxidant response element (EpRE/ARE). We have previously observed that QR is up-regulated by the antiestrogen trans-hydroxytamoxifen in breast cancer cells. QR gene regulation by the antiestrogen-occupied estrogen receptor (ER) is mediated by the EpRE-containing region of the human QR gene, and the ER is one of the complex of proteins that binds to the EpRE. In an effort to further understand the mechanism for ER regulation of QR gene we identified other protein factors that regulate QR gene transcriptional activity in breast cancer cells. One of these protein factors, hPMC2 (human homolog of Xenopus gene which prevents mitotic catastrophe), directly binds to the EpRE and interacts with the ER in yeast genetic screening and in vitro assays. Interestingly hPMC2 interacts more strongly to ER beta when compared with ER alpha. In transient transfection assays using reporter constructs containing the EpRE, hPMC2 alone can slightly activate reporter in ER-negative MDA-MB-231 breast cancer cells. The activation of QR gene activity by hPMC2 is enhanced in the presence of ER beta.