Orphan receptor that acts as transcription activator in the absence of bound ligand. Binds specifically to an estrogen response element and activates reporter genes controlled by estrogen response elements (By similarity). Induces the expression of PERM1 in the skeletal muscle. Homodimer. Binds TLE1, PNRC1 and PNRC2. Binds GRIP1 (By similarity). Interacts with NRIP1, NCOA1 and NCOR2. Expressed in the heart, kidney, brain, lung, bone marrow, adrenal gland, trachea, spinal cord and thyroid gland. Expressed at high levels in fetal brain and also in the fetal kidney, lung and liver. Acetylated by PCAF/KAT2 (in vitro). Sumoylation on Lys-40 is enhanced by phosphorylation at Ser-45 and represses transcriptional activity. Phosphorylation on Ser-45 enhances sumoylation on Lys-40 thus repressing transcriptional activity. No physiological activating ligand is known for this orphan receptor, but 4-hydroxytamoxifen and diethylstilbestrol act as inverse agonists and deactivate ESRRG. Belongs to the nuclear hormone receptor family. NR3 subfamily. Contaminating sequence. Potential poly-A sequence.