Activation of the thyroid hormone receptor α gene promoter by the orphan nuclear receptor ERRα

Abstract

The superfamily of nuclear receptors comprises transcription factors that depend on a ligand for their activity. In addition, the superfamily includes a number of orphan receptors, for which no ligand is known. We report here that the orphan receptor estrogen receptor related alpha receptor (ERRα) stimulates the expression of the thyroid hormone receptor alpha (TRα) gene promoter. We characterized a responsive site that is both necessary and sufficient for ERRα-induced transactivation. In addition, we show that both TRα and ERRα are coexpressed in embryonic intestine, brown fat and heart as well as in the adult gonads. In the testis, expression of both receptors can be found in the seminiferous tubes where it is totally restricted to spermatocytes I. Altogether this suggests that TRα is an in vivo target of ERRα.