Function of estrogen receptor tyrosine 537 in hormone binding, DNA binding, and transactivation.

The human estrogen receptor (hER) is a ligand-activated transcription factor which, like many other members of the nuclear receptor protein family, exhibits a dimerization-dependent transcriptional activation. Several previous reports have provided evidence of the phosphorylation of the hER at tyrosine 537 (Y537). However, the exact function of a putative phosphorylation at this site remains controversial.

The role of phosphorylation in human estrogen receptor function.

We have studied the role of phosphorylation of the human estrogen receptor (hER) at serine 118, which has been previously identified as a site important for transactivation. We have tested this transactivation in yeast and cell-free transcription assays, and have shown that mutation of serine 118 to alanine results in a 30-40% decrease in hER-dependent transcription. Furthermore, we investigated the functional significance of phosphorylation at this site by hormone binding and DNA binding.

Molecular and kinetic basis for the mixed agonist/antagonist activity of estriol.

Estriol acts as a weak estrogen when administered in a single dose into immature or ovariectomized laboratory animals, but produces full estrogenic responses upon chronic administration. However, when estriol is injected together with estradiol it acts as an antiestrogen. We studied the dual agonist/antagonist properties of estriol, using recombinant human estrogen receptor (hER) in ligand-binding assay, cell-free transcription assay, electrophoretic mobility shift assay with cVitII estrogen response element (ERE), and ERE-Sepharose chromatography.

Phosphorylation of serine-167 on the human oestrogen receptor is important for oestrogen response element binding and transcriptional activation.

We have studied the role of phosphorylation of the human oestrogen receptor (hOR; otherwise known as hER) at serine-167, which has been identified previously as the major oestrogen-induced phosphorylation site. We have tested transactivation by the hOR in yeast and cell-free transcription assays, and shown that mutation of serine-167 results in a 70% decrease in hOR-dependent transcription. Furthermore we explored the functional significance of phosphorylation at this site by hormone binding and DNA binding.

Transcriptional activation of the human estrogen receptor by DDT isomers and metabolites in yeast and MCF-7 cells.

In this study, we determined whether the DDT isomers p,p'-DDT [1,1,1,-trichloro-2,2-bis(p-chlorophenyl)ethane], o,p'-DDT [1,1,1-trichloro-2(p-chlorophenyl)-2-(o-chlorophenyl)ethane], and their metabolites p,p'-DDD [1,1-dichloro-2,2-bis(p-chlorophenyl)ethane], o,p'-DDD [1,1-dichloro-2-(p-chlorophenyl)-2-(o-chlorophenyl)ethane], p,p'-DDE [1,1,-dichloro-2,2-bis(p-chlorophenyl)ethylene], o,p'-DDE [1,1-dichloro-2-(p-chlorophenyl)-2-(o-chlorophenyl)ethylene], and p,p'-DDA [2,2-bis(p-chlorophenyl)acetic acid], could bind to and transcriptionally activate the human estrogen receptor (hER). Novel results from competitive binding assays showed that o,p'-DDD, o,p'-DDE, and p,p'-DDT, as well as the established environmental estrogen o,p'-DDT, were able to bind specifically to the hER with approximately 1000-fold weaker affinities for the hER than that of estradiol. In contrast, only o,p'-DDT, but not p,p'-DDT, bound to the rat estrogen receptor.