Human TAFII55 Interacts with the Vitamin D3 and Thyroid Hormone Receptors and with Derivatives of the Retinoid X Receptor That Have Altered Transactivation Properties

• DOI: 10.1128/mcb.19.8.5486
• Publication Date: 2015-10-26T10:19:42Z
• Authors: Anne-Claire Lavigne; Gabrielle Mengus; Yann-Gaël Gangloff; Jean-Marie Wurtz; Irwin Davidson
• Keywords: 0301 basic medicine; Binding Sites; Receptors, Thyroid Hormone; Macromolecular Substances; Receptors, Retinoic Acid; [SDV]Life Sciences [q-bio]; Recombinant Fusion Proteins; Molecular Sequence Data; Ligands; Peptide Fragments; 3. Good health; 03 medical and health sciences; Retinoid X Receptors; Amino Acid Substitution; COS Cells; Chlorocebus aethiops; Mutagenesis, Site-Directed; Animals; Humans; Receptors, Calcitriol; Amino Acid Sequence; Sequence Alignment; Protein Binding; Sequence Deletion

We have identified novel interactions between the human (h)TATA-binding protein-associated factor TAF(II)55 and the ligand-binding domains (LBDs) of the nuclear receptors for vitamin D(3) (VDR) and thyroid hormone (TRalpha). Following expression in Cos cells, hTAF(II)55 interacts with the VDR and TRalpha LBDs in a ligand-independent manner whereas no interactions with the retinoid X receptors (RXRs) or with other receptors were observed. Deletion mapping indicates that hTAF(II)55 interacts with a 40-amino-acid region spanning alpha-helices H3 to H5 of the VDR and TRalpha LBDs but not with the equivalent highly related region of RXRgamma. TAF(II)55 also interacts with chimeric receptors in which the H3-to-H5 region of RXRgamma has been replaced with that of the VDR or TRalpha. Furthermore, replacement of two single amino acids of the RXRgamma LBD with their VDR counterparts allows the RXRgamma LBD to interact with hTAF(II)55 while the corresponding double substitution allows a much stronger interaction. In transfection experiments, the single mutated RXRgamma LBDs activate transcription to fivefold higher levels than wild-type RXRgamma while the double mutation activates transcription to a level comparable to that observed with the VDR. There is therefore a correlation between the ability of the modified RXRs to interact with hTAF(II)55 and transactivation. These results strongly suggest that the TAF(II)55 interactions with the modified RXR LBDs modulate transcriptional activation.