Helix-loop-helix-type transcription factor (HES-1) is expressed in osteoblastic cells, suppressed by 1,25(OH)(2) vitamin D-3, and modulates 1,25(OH)(2) vitamin D-3 enhancement of osteopontin gene expression

The active form of vitamin D, 1,25(OH)(2) vitamin D-3 (D-3), is a potent modulator of osteoblastic function, In this study, we examined, the expression of a negative type basic helix-loop-helix transcription factor, HES 1, in osteoblastic cells and the regulation of its expression by D-3, We found that HES-1 is expressed as a 1.7 kb mRNA in rat osteoblastic osteosarcoma ROS17/2.8 cells, Treatment with D-3 suppressed HES-1 mRNA levels by about 50%, This suppression was observed within 24 h and lasted for at least 48 h, The suppressive effect was dose-dependent starting at 10(-9) mol/L and saturated at 10(-8) mol/L, The vitamin D-3 suppression of HES-1 mRNA level was blocked by actinomycin D as well as cycloheximide, suggesting the involvement of transcriptional control, which requires new protein synthesis, Proteins in the crude nuclear extracts prepared from ROS17/ 2.8 cells bound to the N-box sequence (CACNAG), To examine the function of HES-1 in osteoblasts, HES-1 was overexpressed in ROS17/2.8 cells, Overexpression of HES-1 suppressed the vitamin D-dependent upregulation of osteopontin gene expression in these cells, Vitamin D suppression of HES-1 gene expression was also observed in normal rat calvaria-derived osteoblast-enriched cells, These results indicate that HES-1 is expressed in osteoblastic cells and is involved in vitamin D-3 regulation of osteoblastic gene expression. (C) 1997 by Elsevier Science Inc.