Cloning, chromosomal localization, and functional analysis of the murine estrogen receptor beta.
Estrogen receptor beta (ER beta) is a novel steroid receptor that is expressed in rat prostate and ovary. We have cloned the mouse homolog of ER beta and mapped the gene, designated Estrb, to the central region of chromosome 12. The cDNA encodes a protein of 485 amino acids that shares, respectively, 97% and 60% identity with the DNA- and ligand-binding domains of mouse (m) ER alpha. Mouse ER beta bind to an inverted repeat spaced by three nucleotides in a gel mobility shift assay and transactivates promoters containing synthetic or natural estrogen response elements in an estradiol (E2)-dependent manner. Scatchard analysis indicates that mER beta has slightly lower affinity for E2 [dissociation constant (Kd) = 0.5 nM] when compared with mER alpha (Kd = 0.2 nM). Antiestrogens, including 4-hydroxytamoxifen (OHT), ICI 182,780, and a novel compound, EM-800, inhibit E2-dependent transactivation efficiently. However, while OHT displays partial agonistic activity with ER alpha on a basal promoter linked to estrogen response elements in Cos-1 cells, this effect is not observed with mER beta. Cotransfection of mER beta and H-RasV12 causes enhanced activation in the presence of E2. Mutagenesis of a serine residue (position 60), located within a mitogen-activated protein kinase consensus phosphorylation site abolishes the stimulatory effect of Ras, suggesting that the activity of mER beta is also regulated by the mitogen-activated protein kinase pathway. Surprisingly, the coactivator SRC-1 up-regulates mER beta transactivation both in the absence and presence of E2, and in vitro interaction between SRC-1 and the ER beta ligand-binding domain is enhanced by E2. Moreover, the ligand-independent stimulatory effect of SRC-1 on ER beta transcriptional activity is abolished by ICI 182,780, but not by OHT. Our results demonstrate that while ER beta shares many of the functional characteristics of ER alpha, the molecular mechanisms regulating the transcriptional activity of mER beta may be distinct from those of ER alpha.
Tremblay
G B
GB
Molecular Oncology Group, Boyal Victoria Hospital Montréal, Québec, Canada.
Tremblay
A
A
Copeland
N G
NG
Gilbert
D J
DJ
Jenkins
N A
NA
Labrie
F
F
Giguère
V
V
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D004965:Estrogen Antagonists / Q000494:pharmacology; D047629:Estrogen Receptor beta; D005260:Female; D051548:Histone Acetyltransferases; D051379:Mice; D008969:Molecular Sequence Data; D056920:Nuclear Receptor Coactivator 1; D010053:Ovary; D011960:Receptors, Estrogen / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013629:Tamoxifen / Q000031:analogs & derivatives / Q000494:pharmacology; D014157:Transcription Factors / Q000494:pharmacology; D014158:Transcription, Genetic; D014162:Transfection
D004965:Estrogen Antagonists; D047629:Estrogen Receptor beta; D011960:Receptors, Estrogen; D014157:Transcription Factors; D013629:Tamoxifen; C016601:afimoxifene; D051548:Histone Acetyltransferases; C538861:Ncoa1 protein, mouse; D056920:Nuclear Receptor Coactivator 1