Structural Studies of the Human Retinoic Acid Receptor Gamma Ligand-binding Domain in Complex with Anti-cancer Heteroarotinoids

Abstract

Retinoids play an important role in the therapy and prevention of cancer by interacting with the retinoic acid receptors (RARs) and the retinoid receptors (RXRs), which are ligand-dependent transcription regulators. The ligand-binding domain (LBD; residues 178-423) of hRARg, which specifically binds reinoids, has been cloned with an N-terminal tag containing six histidines and over-expressed in Escherichia coli. The tag allows for the protein purification using nickel chelating chromatography followed by gel filtration chromatography. Currently, expression and purification are being optimized and preliminary crystallization trials are underway with the LBD in complex with all-trans retinoic acid to check the integrity of the construct. Small crystals have been obtained and await characterization by X-ray diffraction. The ultimate goal is to obtain X-ray crystal structures of the LBD in complex with novel anti-cancer heteroarotinoids (SHetA2 and SHetC2). Atomic resolution of the heteroarotinoids interactions with the protein will aid in optimization of the compounds.