Liu Y, Cserjesi P, Nifuji A, Olson E N, Noda M
Department of Molecular Pharmacology, Tokyo Medical and Dental University, Japan.
J Endocrinol. 1996 Dec;151(3):491-9. doi: 10.1677/joe.0.1510491.
Scleraxis is a recently identified transcription factor with a basic helix-loop-helix motif, which is expressed in sclerotome during embryonic development. We have examined the expression of scleraxis mRNA in rat osteoblastic cells and found that the scleraxis gene was expressed as a 1.2 kb mRNA species in osteoblastic osteosarcoma ROS17/2.8 cells. The scleraxis mRNA expression was enhanced by type-beta transforming growth factor (TGF beta) treatment. The TGF beta effect was observed in a dose-dependent manner starting at 0.2 ng/ml and saturating at 2 ng/ml. The effect was time-dependent and was first observed within 12 h and peaked at 24 h. The TGF beta effect was blocked by cycloheximide, while no effect on scleraxis mRNA stability was observed. TGF beta treatment enhanced scleraxis-E box (Scx-E) binding activity in the nuclear extracts of ROS17/2.8 cells. Furthermore, TGF beta enhanced transcriptional activity of the CAT constructs which contain the Scx-E box sequence. TGF beta treatment also enhanced scleraxis gene expression in osteoblast-enriched cells derived from primary rat calvaria. These findings indicated for the first time that the novel helix-loop-helix type transcription factor (scleraxis) mRNA is expressed in osteoblasts and its expression is regulated by TGF beta.
硬骨素是最近发现的一种具有碱性螺旋-环-螺旋基序的转录因子，在胚胎发育过程中于生骨节中表达。我们检测了大鼠成骨细胞中硬骨素mRNA的表达，发现硬骨素基因在成骨肉瘤ROS17/2.8细胞中作为一种1.2 kb的mRNA物种表达。β型转化生长因子（TGF-β）处理可增强硬骨素mRNA的表达。从0.2 ng/ml开始以剂量依赖方式观察到TGF-β效应，在2 ng/ml时达到饱和。该效应呈时间依赖性，在12小时内首次观察到，24小时达到峰值。环己酰亚胺可阻断TGF-β效应，而未观察到对硬骨素mRNA稳定性的影响。TGF-β处理增强了ROS17/2.8细胞核提取物中硬骨素-E盒（Scx-E）结合活性。此外，TGF-β增强了含有Scx-E盒序列的CAT构建体的转录活性。TGF-β处理还增强了源自原代大鼠颅骨的富含成骨细胞的细胞中硬骨素基因的表达。这些发现首次表明，新型螺旋-环-螺旋型转录因子（硬骨素）mRNA在成骨细胞中表达，其表达受TGF-β调节。
