A functional serine 118 phosphorylation site in estrogen receptor-alpha is required for down-regulation of gene expression by 17beta-estradiol and 4-hydroxytamoxifen.
To evaluate the contribution of ERK1/2 phosphorylation of estrogen receptor (ER)-alpha to activation and repression of endogenous genes, we produced stably transfected lines of HeLa cells with functional ERK1/2 pathways that express similar levels of wild-type human ERalpha and ERalpha mutated to inactivate the well-known MAPK site at serine 118 (ERalphaS118A). We compared effects of the S118A mutation on 17beta-estradiol (E(2))-mediated transactivation, which is heavily dependent on activation function (AF) 2 of ERalpha and on 4-hydroxytamoxifen (OHT)-mediated transactivation, which is heavily dependent on AF1, which includes S118. To examine whether S118 was the key ERK/MAPK phosphorylation site in ERalpha action, we compared the effects of the S118A mutant and the ERK inhibitor U0126 on expression of endogenous genes. In several estrogen response element-containing genes, the S118A mutation strongly reduced induction by E(2), and U0126 did not further reduce expression. Expression of another group of estrogen response element-containing genes was largely unaffected by the S118A mutation. The S118A mutation had variable effects on genes induced by ER tethering or binding near specificity protein-1 and activator protein-1 sites. For five mRNAs whose expression is strongly down-regulated by E(2) and partially or completely down-regulated by OHT, the S118A mutation reduced or abolished down-regulation by E(2) and nearly abolished down-regulation by OHT. In contrast, for Sma and mothers against decapentaplegic-3-related, which is down-regulated by E(2) and not OHT, the S118A mutation had little effect. These data suggest that there may be distinct groups of genes down-regulated by ERalpha and suggest a novel role for ERK phosphorylation at serine 118 in AF1 in regulating expression of the set of genes down-regulated by OHT.
Cheng
Jingwei
J
Department of Biochemistry, University of Illinois, 600 South Mathews, Urbana, IL 61801, USA.
Zhang
Chen
C
Shapiro
David J
DJ
D004247:DNA / Q000378:metabolism; D015536:Down-Regulation / Q000502:physiology; D004958:Estradiol / Q000494:pharmacology*; D004965:Estrogen Antagonists / Q000494:pharmacology*; D047628:Estrogen Receptor alpha / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004967:Estrogens / Q000235:genetics; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D006367:HeLa Cells; D006801:Humans; D008024:Ligands; D009154:Mutation; D010766:Phosphorylation; D020218:Response Elements / Q000235:genetics; D013629:Tamoxifen / Q000031:analogs & derivatives* / Q000494:pharmacology; D015533:Transcriptional Activation; D014162:Transfection
D004965:Estrogen Antagonists; D047628:Estrogen Receptor alpha; D004967:Estrogens; D008024:Ligands; D013629:Tamoxifen; C016601:afimoxifene; D004958:Estradiol; D004247:DNA; D048049:Extracellular Signal-Regulated MAP Kinases