Problems with Methods used to Screen Estrogenic Chemicals by Yeast Two-Hybrid Assays.

We developed a yeast two-hybrid assay using a human-type estrogen receptor (hERα) to screen test chemicals reporting weak estrogenic activity at high concentrations. As a result of exposure to several test chemicals, viable yeast cells showed a decrease in number compared with a control. It was shown that this phenomenon was due to fungicidal effects of the test chemicals within the yeast cell or to inhibition of yeast cell proliferation. Therefore, in performing a yeast two-hybrid assay, it is necessary to monitor yeast cell proliferation by methods such as the measurement of the number of viable cells, and it is necessary to screen test chemicals within a concentration range where these chemicals show neither fungicidal effects towards the yeast cell nor inhibition of yeast cell proliferation.