Parathyroid hormone (PTH) suppresses rat PTH/PTH-related protein receptor gene promoter

Parathyroid hormone (PTH) regulates osteoblasts via a G protein-linked PTH/ PTH-related protein (PTHrP) receptor. PTH effects on PTH/PTHrP receptor gen e expression were studied in UMR 106 osteoblast-like cells. In heterogeneou s nuclear RNA and Northern analysis, PTH suppressed PTH/PTHrP receptor tran scription. We cloned the 7-kb promoter region of the rat PTH/PTHrP receptor gene and transiently transfected chimeric deletion constructs containing t he 5 ' -flanking region and the luciferase gene into UMR 106 cells. In tran sfected cells the minimal region for basal promoter activity was between po sitions -128 and +103. The 5 ' -flanking region of exon U1 contained severa l putative-binding sites for Sp1 and the myc-associated zinc finger protein (MAZ). The minimal PTH-suppressive region (PTHSR) was between +1 and +25 i n exon U1, but the 5 ' -flanking region or Sp1 and MAZ-binding sites also w ere required for PTH-mediated repression. By gel mobility shift assay PTH m arkedly decreased binding of PTHSR-protein complex in UMR 106 cells. The mu tation experiments showed that the most critical sequence for the repressio n of PTH was 5 ' -GGGGGAGGGGAG-3 ' (+1 to +12) of PTHSR. This represents th e first characterization of a PTH-suppressive region of the PTH/PTHrP recep tor gene in rat. (C) 2001 Academic Press.