The T-box near the zinc fingers of the human vitamin D receptor is required for heterodimeric DNA binding and transactivation.
The T-box mediates binding of retinoid X receptor (RXR) homodimers to DNA while the P- and D-box in the zinc fingers of steroid hormone receptors play roles in DNA-binding specificity and homodimerization, respectively. We investigated the function of these elements in the human vitamin D receptor (hVDR) by mutating a Lys-Glu pair of amino acids in the T-box, and by altering the P- and D-boxes to the corresponding residues of the glucocorticoid receptor (GR). The T-box mutant hVDR displayed attenuated vitamin D responsive element (VDRE) binding in the presence of RXR and was severely compromised in transcriptional activation. In contrast, GR P/D-box mutant hVDRs bound to the rat osteocalcin VDRE and elicited near normal transcriptional activation. The T-box mutant uniquely exhibited dominant negative properties, highlighting the significance of this region of hVDR for heterodimeric transcriptional activation.
Hsieh
J C
JC
Department of Biochemistry, College of Medicine, University of Arizona, Tucson 85724, USA.
Jurutka
P W
PW
Selznick
S H
SH
Reeder
M C
MC
Haussler
C A
CA
Whitfield
G K
GK
Haussler
M R
MR
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D004247:DNA / Q000378:metabolism*; D006801:Humans; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D051381:Rats; D018167:Receptors, Calcitriol / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship; D015533:Transcriptional Activation; D014162:Transfection; D016335:Zinc Fingers
D046911:Macromolecular Substances; D018167:Receptors, Calcitriol; D004247:DNA