Cloning, Chromosomal Localization, and Functional Analysis of the Murine Estrogen Receptor  

Abstract

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.

Changes in the expression of neurohypophyseal prolactins during the estrous cycle and after estrogen treatment

“…The 'original' estrogen receptor, now known as ER , has been located in few of these neurons which, in turn, preferentially locate the newly identified ER (Simerly et al 1990, Alves et al 1998. Although both ERs are capable of activating gene transcription by binding to an estrogen response element (Tremblay et al 1997), recent evidence showed that ER and ER mediated estrogen-induced activation and inhibition of transcription respectively (Paech et al 1997). A differential activation of either ER within the magnocellular neurosecretory system could contribute to a different mechanism operating PRL gene expression at this site.…”

Attenuation of estrogen receptor α-mediated transcription through estrogen-stimulated recruitment of a negative elongation factor

“…The following luciferase reporters were used: C3-luciferase (Norris et al 1996), pS2-luciferase (Green and Chambon 1986), pS2⌬ERE-luc (Tremblay et al 1997), CATD-luciferase (Wu et al 1998), Gal4-luciferase (Salghetti et al 1999), and AP1-luciferase (Stratagene).…”

Mutual antagonism of estrogen receptors alpha and beta and their preferred interactions with steroid receptor coactivators in human osteoblastic cell lines

“…The effects of estrogen were initially considered to be mediated by a single estrogen receptor (ER ) (Mangelsdorf et al 1995); however, a second estrogen receptor (ER ) that increases the potential diversity of estrogen responses was discovered (Kuiper et al 1996, Mosselman et al 1996, Tremblay et al 1997. The two ER isoforms function by binding 17 -estradiol (E2) with high affinity.…”