GeneBLAzer®TR beta DA(Division Arrested) cells and TR beta-UAS-bla HEK 293T cells contain the ligand-binding domain (LBD) of the human Thyroid hormone receptor beta (TR beta) fused to the DNA-binding domain of GAL4 stably integrated in the GeneBLAzer®UASbla HEK 293T cell line. GeneBLAzer®UAS-bla HEK 293T cells stably express a betalactamase reporter gene under the transcriptional control of an upstream activator sequence (UAS). When an agonist binds to the LBD of the GAL4 (DBD)-TR beta (LBD) fusion protein, the protein binds to the UAS, resulting in expression of beta-lactamase. Division Arrested (DA) cells are available in two configurations- an Assay Kit (which includes cells and sufficient substrate to analyze 1 x 384-well plate), and a tube of cells sufficient to analyze 10 x 384-well plates. DA cells are irreversibly division arrested using a low-dose treatment of Mitomycin-C, and have no apparent toxicity or change in cellular signal transduction. Both TR beta DA cells and TR beta-UAS-bla HEK 293T cells are functionally validated for Z' and EC50 concentrations of T3 Thryoid hormone. In addition, TR beta-UAS-bla HEK 293T cells have been tested for assay performance under variable conditions, including DMSO concentration, cell number, stimulation time, and substrate loading time (data available upon request). Additional testing data using alternate stimuli are also available.