title: Hormone-independent transcriptional activation and coactivator binding by novel orphan nuclear receptor ERR3.
abstract: Orphan nuclear receptors share sequence homology with members of the nuclear receptor superfamily, but ligands are unknown or unnecessary. A novel orphan receptor, estrogen receptor-related protein 3 (ERR3), was identified by yeast two-hybrid screening, using the transcriptional coactivator glucocorticoid receptor interacting protein 1 (GRIP1) as bait. The putative full-length mouse ERR3 contains 458 amino acids and is closely related to two known orphan receptors ERR1 and ERR2. All the ERR family members share an almost identical DNA-binding domain, which has 68% amino acid identity with that of estrogen receptor. ERR3 bound specifically to an estrogen response element and activated reporter genes controlled by estrogen response elements, both in yeast and in mammalian cells, in the absence of any added ligand. A conserved AF-2 activation domain located in the hormone-binding domain of ERR3 was primarily responsible for transcriptional activation. The ERR3 AF-2 domain bound GRIP1 in a ligand-independent manner both in vitro and in vivo, through the LXXLL motifs of GRIP1, and GRIP1 functioned as a transcriptional coactivator for ERR3 in both yeast and mammalian cells. Expression of ERR3 in adult mouse was restricted; highest expression was observed in heart, kidney, and brain. In the mouse embryo no expression was observed at day 7, and highest expression occurred around the 11-15 day stages. Although ERR3 is much more closely related to ERR2 than to ERR1, the expression pattern for ERR3 was similar to that of ERR1 and distinct from that for ERR2, suggesting a unique role for ERR3 in development.
authors.affiliation: Department of Pathology, University of Southern California, Los Angeles, California 90033, USA.
authors.forename: H
authors.initials: H
authors.lastname: Hong
authors.forename: L
authors.initials: L
authors.lastname: Yang
authors.forename: M R
authors.initials: MR
authors.lastname: Stallcup
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000378:metabolism; D004967:Estrogens; D017930:Genes, Reporter; D008024:Ligands; D051379:Mice; D008969:Molecular Sequence Data; D051958:Nuclear Receptor Coactivator 2; D011485:Protein Binding; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism*; D020218:Response Elements; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D000097983:ERRalpha Estrogen-Related Receptor
chemical_list: D004268:DNA-Binding Proteins; D004967:Estrogens; D008024:Ligands; D051958:Nuclear Receptor Coactivator 2; D018160:Receptors, Cytoplasmic and Nuclear; D011960:Receptors, Estrogen; D014157:Transcription Factors; D000097983:ERRalpha Estrogen-Related Receptor; C098925:Esrrb protein, mouse; C490916:Esrrg protein, mouse; C498002:Ncoa2 protein, mouse