A central dinucleotide within vitamin D response elements modulates DNA binding and transactivation by the vitamin D receptor in cellular response to natural and synthetic ligands.
There is considerable divergence in the sequences of steroid receptor response elements, including the vitamin D response elements (VDREs). Two major VDRE-containing and thus 1,25-dihydroxyvitamin D(3) (1,25-(OH)(2)D(3))-regulated genes are the two non-collagenous, osteoblast-derived bone matrix proteins osteocalcin and osteopontin. We observed a stronger induction of osteopontin than osteocalcin mRNA expression by 1,25-(OH)(2)D(3). Subsequently, we have shown that vitamin D receptor/retinoid X receptor alpha (VDR/RXRalpha) heterodimers bind more tightly to the osteopontin VDRE than to the osteocalcin VDRE. Studies using point mutants revealed that the internal dinucleotide at positions 3 and 4 of the proximal steroid half-element are most important for modulating the strength of receptor binding. In addition, studies with VDRE-driven luciferase reporter gene constructs revealed that the central dinucleotide influences the transactivation potential of VDR/RXRalpha with the same order of magnitude as that observed in the DNA binding studies. The synthetic vitamin D analog KH1060 is a more potent stimulator of transcription and inducer of VDRE binding of VDR/RXR in the presence of nuclear factors isolated from ROS 17/2.8 osteoblast-like cells than the natural ligand 1,25-(OH)(2)D(3). Interestingly, however, KH1060 is comparable or even less potent than 1,25-(OH)(2)D(3) in stimulating VDRE binding of in vitro synthesized VDR/RXRalpha. Thus, the extent of 1,25-(OH)(2)D(3)- and KH1060-dependent binding of VDR/RXRalpha is specified by a central dinucleotide in the VDRE, and the ligand-induced effects on DNA binding are in part controlled by the cellular context of nuclear proteins.
van den Bemd
Gert-Jan C M
GJ
Department of Internal Medicine, Erasmus Medical Center, 3015 GD Rotterdam, The Netherlands.
Jhamai
Mila
M
Staal
Ada
A
van Wijnen
Andre J
AJ
Lian
Jane B
JB
Stein
Gary S
GS
Pols
Huibert A P
HA
van Leeuwen
Johannes P T M
JP
D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D024202:Electrophoretic Mobility Shift Assay; D006801:Humans; D008024:Ligands; D015675:Osteocalcin / Q000235:genetics; D053495:Osteopontin; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics; D018167:Receptors, Calcitriol / Q000737:chemistry / Q000378:metabolism*; D018168:Receptors, Retinoic Acid / Q000737:chemistry / Q000378:metabolism*; D047488:Retinoid X Receptors; D012795:Sialoglycoproteins / Q000235:genetics; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured; D030181:Vitamin D Response Element
D017931:DNA Primers; D008024:Ligands; D012333:RNA, Messenger; D018167:Receptors, Calcitriol; D018168:Receptors, Retinoic Acid; D047488:Retinoid X Receptors; C506895:SPP1 protein, human; D012795:Sialoglycoproteins; D014157:Transcription Factors; D015675:Osteocalcin; D053495:Osteopontin