Identification of the promoter region of the parathyroid hormone receptor gene responsible for transcriptional suppression by insulin-like growth factor-I.
We investigated parathyroid hormone (PTH)/PTH-related protein receptor (PTH1R) gene suppression induced by insulin-like growth factor (IGF)-I using a rat osteoblast-like cell line (UMR-106). Observations were made with PD98059, a specific ERK signaling pathway inhibitor, and UMR-106 cells transfected with dominant negative or constitutively active forms of MAP kinase kinase. IGF-I inhibited PTH1R gene expression via an ERK1/2 MAP kinase pathway. We cloned the 8-kb promoter region of the rat PTH1R gene and characterized the U3 promoter, a major IGF-I-responsive promoter among the two present in rat osteoblasts. The IGF-I-suppressive region was between +1 and +25, identical to the previously described PTH-suppressive region (PTHSR). Gel mobility-shift detected a specific DNA-protein complex decreased by IGF-I. Mutation involving a three base sequence (+1 to +3) among more than 3.5 kb constituting the PTH1R promoter region completely abolished IGF-I action. Thus, IGF-I signaling may act at the osteoblast exon U3 transcription initiation site to repress the transcriptional activity.
Kawane
Tetsuya
T
Section of Biochemistry, Department of Oral Function and Molecular Biology, Ohu University School of Dentistry, Koriyama 963-8611, Japan.
Mimura
Junsei
J
Fujii-Kuriyama
Yoshiaki
Y
Horiuchi
Noboru
N
D000818:Animals; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D005091:Exons / Q000235:genetics / Q000502:physiology; D005419:Flavonoids / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000235:genetics; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D009154:Mutation / Q000502:physiology; D010006:Osteoblasts / Q000502:physiology*; D011401:Promoter Regions, Genetic / Q000235:genetics / Q000502:physiology*; D051381:Rats; D044168:Receptor, Parathyroid Hormone, Type 1 / Q000096:biosynthesis* / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects* / Q000235:genetics
D005419:Flavonoids; D044168:Receptor, Parathyroid Hormone, Type 1; D007334:Insulin-Like Growth Factor I; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one