Estrogen-modulated estrogen receptor x Pit-1 protein complex formation and prolactin gene activation require novel protein synthesis.
Both estrogen receptor (ER) and Pit-1 proteins are essential for the estrogen-activated expression of the rat prolactin gene. Our results show that ER.Pit-1 protein complex formation is reduced by estrogen in GH3 and PR1 rat pituitary tumor cells. In the latter, this decrease was blocked by cycloheximide, a protein synthesis inhibitor. On the other hand, the direct addition of estrogen to PR1 cell lysates had no effect on the formation of ER.Pit-1 complexes. Estrogen-activated prolactin gene expression was also inhibited by cycloheximide, suggesting that some form of protein synthesis is involved in ER.Pit-1 complex formation and subsequent prolactin gene activation. In support of this notion, we showed that estrogen-induced regulation of ER.Pit-1 complex formation could be transferred from cell lysates prepared from estrogen-treated PR1 cells to control cell lysates. This is not true for GH3 cells; instead, direct administration of estrogen to GH3 cell lysates readily abolished ER.Pit-1 protein complex formation in a dose-dependent manner, and such estrogen-induced regulation was blocked by the antiestrogen ICI 182,780. These findings thus indicate that 1) interaction between ER and Pit-1 proteins is estrogen-regulated in ways specific to different cell types, and 2) auxiliary protein factor synthesis may be involved in this process.
Ying
C
C
Department of Microbiology, Soochow University, Taipei, Taiwan 111, Republic of China. cying@mail.scu.edu.tw
Lin
D H
DH
D000818:Animals; D003513:Cycloheximide / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004054:Diethylstilbestrol / Q000494:pharmacology*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D007700:Kinetics; D010052:Ovariectomy; D010911:Pituitary Neoplasms; D011388:Prolactin / Q000235:genetics*; D051381:Rats; D011916:Rats, Inbred F344; D011960:Receptors, Estrogen / Q000378:metabolism*; D050817:Transcription Factor Pit-1; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; C494186:Pou1f1 protein, rat; D011960:Receptors, Estrogen; D050817:Transcription Factor Pit-1; D014157:Transcription Factors; D004054:Diethylstilbestrol; D011388:Prolactin; D003513:Cycloheximide