Specific mutations in the estrogen receptor change the properties of antiestrogens to full agonists.
The estrogen receptor (ER) stimulates transcription of target genes by means of its two transcriptional activation domains, AF-1 in the N-terminal part of the receptor and AF-2 in its ligand-binding domain. AF-2 activity is dependent upon a putative amphipathic alpha-helix between residues 538 and 552 in the mouse ER. Point mutagenesis of conserved hydrophobic residues within this region reduces estrogen-dependent transcriptional activation without affecting hormone and DNA binding significantly. Here we show that these mutations dramatically alter the pharmacology of estrogen antagonists. Both tamoxifen and ICI 164,384 behave as strong agonists in HeLa cells expressing the ER mutants. In contrast to the wild-type ER, the mutant receptors maintain nuclear localization and DNA-binding activity after ICI 164,384 treatment. Structural alterations in AF-2 caused by gene mutations such as those described herein or by estrogen-independent signaling pathways may account for the insensitivity of some breast cancers to tamoxifen treatment.
Mahfoudi
A
A
Institut de Biologie Animale, Université de Lausanne, Switzerland.
Roulet
E
E
Dauvois
S
S
Parker
M G
MG
Wahli
W
W
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D002645:Chickens; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017686:Oncorhynchus mykiss; D017354:Point Mutation; D053284:Polyunsaturated Alkamides; D017433:Protein Structure, Secondary; D051381:Rats; D011960:Receptors, Estrogen / Q000819:agonists / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000819:agonists / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013629:Tamoxifen / Q000031:analogs & derivatives* / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D014981:Xenopus
D004268:DNA-Binding Proteins; D004965:Estrogen Antagonists; D053284:Polyunsaturated Alkamides; D011960:Receptors, Estrogen; D011994:Recombinant Proteins; D013629:Tamoxifen; C016601:afimoxifene; D004958:Estradiol; C051781:ICI 164384