||This nuclear receptor assay system utilizes proprietary human mammalian cells engineered to provide high-level expression of a hybrid form of the human estrogen-related receptor alpha (NR3B1). The N-terminal DNA binding domains (DBD) of the native ERRα has been substituted with that of the yeast GAL4-DBD. The reporter gene is beetle luciferase functionally linked to the GAL4 upstream activation sequence (UAS). As is true in vivo, these reporter cells express ERRα in a constant state of high-level activity. The principal application of this assay system is in the screening of test samples to quantify inverse-agonist activities that they may exert against human ERRα. ERRα reporter cells are prepared using the proprietary CryoMite process. This cryo-preservation method yields exceptional cell viability post-thaw, and provides the convenience of immediately dispensing healthy, division-competent reporter cells into assay plates. There is no need for cumbersome intermediate treatment steps such as spin-and-rinse of cells, viability determinations, cell titer adjustments, or the preincubation of reporter cells prior to assay setup. The nuclear receptor reporter assays are all-inclusive cell-based assay systems. In addition to ERRα reporter cells, this kit provides two optimized media for use during cell culture and in diluting the user"s test samples, a reference inverse-agonist, reagents to prepare luciferase detection reagent, and a cell culture-ready assay plate.