Repression of the alpha-fetoprotein gene promoter by progesterone and chimeric receptors in the presence of hormones and antihormones.

Using transient transfection assays, we showed that repression of the alpha-fetoprotein promoter by intact and deletion mutants of the progesterone receptor and by chimeric progesterone/glucocorticoid-estrogen receptors in the presence of their cognate hormones was closely correlated with their ability to bind to a progesterone/glucocorticoid-responsive element. This negative regulation was also observed in the presence of antihormones, providing evidence that receptor-antihormone complexes can bind to their responsive elements in vivo.