Nuclear Factors Enhance the Binding of Estrogen Receptor to Estrogen Response Element

We obtained the full length of human estrogen receptor (hER) through the in vitro translation. It was shown that the translated product could bind to the estrogen response element (ERE). The nuclear extract prepared from the rat uterus after ovariectomy could enhance the binding of hER-ERE in an estrogen dependent manner. However, the enhancing effect was sharply decreased when the nuclear extract was pre-incubated at 50 degrees for 15 minutes before being used for the binding reaction. These results indicated the presence in the rat uterus extracts after ovariectomy of a heat labile factor that can enhance the binding of hER-ERE in an estrogen-dependent manner. The DNA binding domain of estrogen receptor (ER DBD) fused to the Scistosoma japonicam glutathione S-transferase (GST) was expressed in the E. coli. The expression product also could bind the ERE. However, the binding was not affected by the uterine extract, indicating that the heat-sensitive nuclear factors may interact with hER outside the DBD to enhance the binding of ER to ERE.