Human TAF(II)55 interacts with the vitamin D(3) and thyroid hormone receptors and with derivatives of the retinoid X receptor that have altered transactivation properties.
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.
Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP, Illkirch Cédex, C.U. de Strasbourg, France.
A C
AC
Lavigne
G
G
Mengus
Y G
YG
Gangloff
J M
JM
Wurtz
I
I
Davidson
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002522:Chlorocebus aethiops; D006801:Humans; D008024:Ligands; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000378:metabolism; D011485:Protein Binding; D018167:Receptors, Calcitriol / Q000378:metabolism*; D018168:Receptors, Retinoic Acid / Q000235:genetics / Q000378:metabolism*; D011988:Receptors, Thyroid Hormone / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D047488:Retinoid X Receptors; D016415:Sequence Alignment; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D035381:TATA-Binding Protein Associated Factors; D015534:Trans-Activators / Q000378:metabolism*; D035362:Transcription Factor TFIID; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection
D008024:Ligands; D046911:Macromolecular Substances; D010446:Peptide Fragments; D018167:Receptors, Calcitriol; D018168:Receptors, Retinoic Acid; D011988:Receptors, Thyroid Hormone; D011993:Recombinant Fusion Proteins; D047488:Retinoid X Receptors; C091537:TAF7 protein, human; D035381:TATA-Binding Protein Associated Factors; D015534:Trans-Activators; D035362:Transcription Factor TFIID; D014157:Transcription Factors