Colocalization and Ligand-Dependent Discrete Distribution of the Estrogen Receptor (ER)α and ERβ

Abstract

To investigate the relationships between the loci expressing functions of estrogen receptor (ER)alpha and that of ERbeta, we analyzed the subnuclear distribution of ERalpha and ERbeta in response to ligand in single living cells using fusion proteins labeled with different spectral variants of green fluorescent protein. Upon activation with ligand treatment, fluorescent protein-tagged (FP)-ERbeta redistributed from a diffuse to discrete pattern within the nucleus, showing a similar time course as FP-ERalpha, and colocalized with FP-ERalpha in the same discrete cluster. Analysis using deletion mutants of ERalpha suggested that the ligand-dependent redistribution of ERalpha might occur through a large part of the receptor including at least the latter part of activation function (AF)-1, the DNA binding domain, nuclear matrix binding domain, and AF-2/ligand binding domain. In addition, a single AF-1 region within ERalpha homodimer, or a single DNA binding domain as well as AF-1 region within the ERalpha/ERbeta heterodimer, could be sufficient for the cluster formation. More than half of the discrete clusters of FP-ERalpha and FP-ERbeta were colocalized with hyperacetylated histone H4 and a component of the chromatin remodeling complex, Brg-1, indicating that ERs clusters might be involved in structural changes of chromatin.

Reprogramming of the SWI/SNF complex for co-activation or co-repression in prohibitin-mediated estrogen receptor regulation

“…Brg1 and Brm are required for transcriptional repression of ER-driven genes by estrogen antagonists It has been reported that Brg1 is involved in ERmediated transcriptional activation (DiRenzo et al, 2000;Belandia et al, 2002;Matsuda et al, 2002). We recently established that a tumor suppressor, prohibitin, and its co-repressors Brg1 and Brm, are required for estrogen antagonist-induced growth suppression (Wang et al, 2002b.…”

Role of CBP in regulating HIF-1-mediated activation of transcription

“…Accumulation foci in the nucleus have been extensively reported for nuclear hormone receptors after addition of ligand (Fejes-Toth et al, 1998;Georget et al, 1997;Htun et al, 1996;Htun et al, 1999;Prufer et al, 2000;Racz and Barsony, 1999;Stenoien et al, 2000). Moreover, coactivators or components of chromatin remodeling complexes have been shown to be recruited to these liganddependent foci (Matsuda et al, 2002;Rivera et al, 2003;Stenoien et al, 2000;Stenoien et al, 2001). In order to further characterize accumulation foci containing proteins involved in the HIF-1α-mediated transactivation response in hypoxic cells we investigated if RNA polymerase IIo, the hyperphosphorylated form of RNA polymerase II, was present in some of the foci.…”

Age-related changes in the expression of ER-β mRNA in the female rat brain

“…Moreover, it has been reported that the ER-α protein and the ER-β mRNA are co-localized in neurons in the rat brain (Shughrue et al, 1998;Orikasa et al, 2002), and the activity of estrogenic compounds may depend, in part, on whether a cell contains ER-α, β, or both. In addition, it is known that ERs form homo-or heterodimers (Cowley et al, 1997;Pace et al, 1997;Pettersson et al, 1997;Ogawa et al, 1998;Matsuda et al, 2002). There is a possibility that estrogen demonstrates different physiological actions via homo-or heterodimers, and the formation of dimers may be affected by decreased levels of ER-β in the specific brain regions in which decreases were observed in aged female rats.…”

“…ER-β mRNA was shown to be co-expressed with ER-α immunoreactivity in the same neuron in several brain regions: the bed nucleus of the stria terminalis, medial amygdaloid nucleus, periventricular preoptic nucleus, medial preoptic nucleus, and anteroventral periventricular nucleus (Shughrue et al, 1998;Orikasa et al, 2002). In addition, in vitro studies have shown that ER-β can form heterodimers with ER-α (Cowley et al, 1997;Pace et al, 1997;Pettersson et al, 1997;Ogawa et al, 1998;Matsuda et al, 2002), 5 suggesting that estrogen may differentially modulate the activity of certain neuronal populations depending on whether the cells express ER-α, ER-β or both (Shughrue et al, 1998). ER-β mRNA is also highly distributed in several rat brain regions, including the olfactory bulb, cerebral cortex, paraventricular hypothalamic nucleus, supraoptic nucleus, hippocampus and cerebellar Purkinje cells, areas that contain little or no ER-α mRNA (Simerly et al, 1990;Shughrue et al, 1997;Mufson et al, 1999;Shima et al, 2003;Mehra et al, 2005).…”