DNA sequences in the rat parathyroid hormone-related peptide gene responsible for 1,25-dihydroxyvitamin D3-mediated transcriptional repression.
Expression of the gene encoding PTH-related peptide (PTHrP), a protein that plays a primary role in the development of humoral hypercalcemia of malignancy, is down-regulated at the transcriptional level by 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]. Deletions of the 5'-flanking region of the rat PTHrP gene, when fused to the chloramphenicol acetyl-transferase gene and transfected into ROS 17/2.8 (rat osteosarcoma) cells, showed that the 1,25-(OH)2D3 responsive region is located between -1.05 and -0.71 kb upstream of the transcription start site. Further mapping of this region revealed that a 123-bp fragment is able to confer 1,25-(OH)2D3 responsiveness to a heterologous (SV40) promoter. This region contains two potential vitamin D response elements (VDREs). One of these motifs resembles the negative VDRE (nVDRE) from the PTH gene, which is also down-regulated by vitamin D3. The other element resembles the canonical VDRE (two hexanucleotide motifs separated by three nucleotides), which has been characterized in a number of genes whose expression is modulated by vitamin D3. Electrophoretic mobility shift assays using nuclear extracts from ROS 17/2,8 cells and from vitamin D receptor. (VDR)-enriched COS 1 cells revealed that both elements interact with the VDR. This protein-DNA interaction is disrupted by an anti-VDR antibody. Therefore, modulation of PTHrP gene transcription by 1,25-(OH)2D3 is mediated by the VDR interacting with one or both of the identified motifs in the 5'-flanking sequence of the gene.
Falzon
M
M
Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston 77555, USA.
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002117:Calcitriol / Q000378:metabolism*; D015536:Down-Regulation; D004586:Electrophoresis / Q000379:methods; D005786:Gene Expression Regulation; D044162:Parathyroid Hormone-Related Protein; D011506:Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D018167:Receptors, Calcitriol / Q000737:chemistry / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic; D014807:Vitamin D / Q000378:metabolism
D044162:Parathyroid Hormone-Related Protein; D011506:Proteins; D018167:Receptors, Calcitriol; D014807:Vitamin D; D002117:Calcitriol