1,25-(OH)2-vitamin D3 suppresses the bone-related Runx2/Cbfa1 gene promoter.
The steroid hormone 1,25-(OH)2-vitamin D3 (VD3) regulates osteoblast differentiation by either activating or repressing transcription of numerous bone phenotypic genes. We addressed whether VD3 also influences osteogenesis by controlling activity of the runt-related transcription factor Runx2/Cbfa1, a key regulator of bone formation in vivo. Our data showed that expression of Runx2 was downregulated by VD3 within 24 h in MC3T3 and ROS 17/2.8, but not in ROS 24.1 cells, which lack a functional vitamin D receptor (VDR). Transient transfection assays showed that the initial 0.6 kb of the bone-related rat and mouse Runx2 promoters both exhibited a 50% reduction of promoter activity in response to VD3 in osteoblastic cells. Furthermore, VD3 inhibited Runx2 transcription in ROS 24.1 cells only upon forced expression of the VDR. Gel mobility shift assays with antibodies and oligonucleotide competition experiments demonstrated that proximal promoter sequences (-92 to -16) contain a functional VD3-responsive element (VDRE) that binds a VDR/retinoid X receptor heterodimer. Mutation of this VDRE completely abolished responsiveness of the Runx2 promoter to VD3 treatment. Together these studies establish that Runx2 expression is regulated by VD3. This VD3-mediated suppression of Runx2 activity provides regulatory coupling between tissue-specific and steroid hormone-dependent control of genes during bone formation.
Drissi
Hicham
H
Department of Cell Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA.
Pouliot
Arlyssa
A
Koolloos
Christian
C
Stein
Janet L
JL
Lian
Jane B
JB
Stein
Gary S
GS
van Wijnen
André J
AJ
D000818:Animals; D001483:Base Sequence / Q000187:drug effects / Q000502:physiology; D001665:Binding Sites / Q000187:drug effects / Q000235:genetics; D001846:Bone Development / Q000187:drug effects / Q000235:genetics*; D002117:Calcitriol / Q000378:metabolism* / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D050659:Core Binding Factor Alpha 1 Subunit; D019281:Dimerization; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D009154:Mutation / Q000187:drug effects / Q000502:physiology; D009363:Neoplasm Proteins; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000502:physiology*; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D018167:Receptors, Calcitriol / Q000187:drug effects / Q000378:metabolism; D018168:Receptors, Retinoic Acid / Q000187:drug effects / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology*; D014407:Tumor Cells, Cultured; D030181:Vitamin D Response Element / Q000187:drug effects / Q000235:genetics
D050659:Core Binding Factor Alpha 1 Subunit; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D018167:Receptors, Calcitriol; D018168:Receptors, Retinoic Acid; D014157:Transcription Factors; D002117:Calcitriol