INDIGO’s Human Retinoic Acid Receptor Beta (RARβ) Reporter Assay System utilizes proprietary mammalian cells engineered to provide constitutive, high-level expression of human RARβ (NR1B2), a ligand-dependent transcription factor. Because these cells incorporate a responsive luciferase reporter gene, quantifying expressed luciferase activity provides a sensitive surrogate measure of RARβ activity in treated cells. The primary application of this reporter assay system is in the screening of test samples to quantify functional activity, either agonist or antagonist, that they may exert against human RARβ.

Retinoic acid receptors (RARs) are nuclear hormone receptors of the NRB1 class, which function as heterodimers with retinoid X receptors (RXRs). There are three distinct RAR subtypes; RARalpha, RARbeta and RARgamma. RARalpha is present in most tissue types, whereas RARbeta and RARgamma expression is more selective. RXR-RAR heterodimers act as ligand-dependent transcriptional regulators by binding to the specific retinoic acid response element (RARE) found in the promoter regions of target genes. In the absence of an RAR agonist, RXR-RAR recruits co-repressor proteins such as NCoR and associated factors such as histone deacetylase to maintain a condensed chromatin structure. RAR agonist binding stimulates co-repressor release and co-activator complexes, such as histone acetyltransferase, are recruited to activate transcription. RARs transduce retinoid signals in vivo, which mediates proper embryogenesis, differentiation and growth arrest. Specifically, RXRalpha-RARgamma heterodimers are necessary for growth arrest and viseral and primitive endodermal differentiation, whereas RXRalpha-RARalpha is required for cAMP-dependent parietal endodermal differentiation. In vitro it has been difficult to elucidate the roles of individual subtypes as functional RAR knockouts generate artificial redundancies that are thought not to exist under normal conditions.

For more information on RARβ, visit the Nuclear Receptor Resource.