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

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.

Rapid and estrogen receptor beta mediated actions in the hippocampus mediate some functional effects of estrogen

“…The original ER identified E 2 binding site [42] is now referred to as ERα, after a second form of ER, called ERβ, was identified in rat prostate and uterine tissue [57][58]. ERα and ERβ are homologous in their DNA (97%) and ligand-binding (60%) domains [58], but are located on different chromosomes and with distinct N-terminal regions encoded by these different genes [57][58][59][60][61][62]. Indeed, there are differences between expression of ERα and ERβ, which suggests that there may be different functional effects of these isoforms.…”

Estrogen receptor β acts as a dominant regulator of estrogen signaling

“…Both ERs bind tamoxifen with comparable a nity but a lack of agonistic e ect of tamoxifen on ERb has been reported, suggesting a functional di erence between the two receptor subtypes (Tremblay et al, 1997;Watanabe et al, 1997).…”

“…The new receptor was named ERb to distinguish it from the previous one, consequently named ERa. Subsequently, human and mouse homologs of ERb were isolated (Mosselman et al, 1996;Pettersson et al, 1997;Tremblay et al, 1997). ERb displays extensive sequence similarity to ERa, most notable in the DBD where the amino acid identity is 97% whereas the LBD shows an overall 55% similarity to ERa.…”

“…ERb has been reported to have weaker transcriptional activity in response to E 2 compared to ERa in transient co-transfection assays in several cell systems (Cowley et al, 1997;Pettersson et al, 1997;Watanabe et al, 1997). ERb also, in contrast to ERa, fails to show agonistic response to the well known anti-estrogen tamoxifen (Tremblay et al, 1997;Watanabe et al, 1997). Recently ERa, but not ERb, was demonstrated to bind to and activate transcription from the DNA core element known as an SF1 (Steroidogenic Factor 1) response element, thus demonstrating functional di erences between the ERs also at the DNA binding level (Vanacker et al, 1999).…”

Oestrogen receptor β expression and depth of myometrial invasion in human endometrial cancer

“…These two receptors share about 95% homology in the DNA binding domain and 55% homology in the ligand binding domain, bind to a consensus oestrogen response element (ERE) (Tremblay et al, 1997) and have similar ligand binding properties (Kuiper et al, 1997). The reverse transcription polymerase chain reaction (RT-PCR) has revealed that ER-β is expressed at high levels in the prostate and ovary (Kuiper et al, 1996;Mosselman et al, 1996), and at moderate levels in many other tissues, including the testis and the uterus, parts of which also seem to express ER-β (Kuiper et al, 1997).…”