Xie W F, Zhang X, Sakano S, Lefebvre V, Sandell L J
Department of Orthopaedic Surgery, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
J Bone Miner Res. 1999 May;14(5):757-63. doi: 10.1359/jbmr.1999.14.5.757.
The transcription factor Sox9 is capable of enhancing type II collagen gene expression and may play a crucial role in chondrogenesis. To determine whether Sox9 is an inducer of the chondrocyte phenotype, we investigated the role of Sox9 in transcription of another cartilage gene encoding the cartilage-derived retinoic acid-sensitive protein (CD-RAP). CD-RAP is specifically expressed during chondrogenesis. We show here that Sox9 protein is able to bind to a SOX consensus sequence in the CD-RAP promoter. Mutation of the SOX motif led to decreased transcription of a CD-RAP promoter construct in chondrocytes. Overexpression of SOX9 resulted in a dose-dependent increased activity of CD-RAP promoter-driven reporter gene in both chondrocytes and nonchondrogenic cells. A truncated SOX9, which contains a binding domain but no trans-activation function, inhibited CD-RAP promoter activity. Overexpression of SOX9 increased the level of endogenous CD-RAP mRNA in chondrocytes, but was unable to induce endogenous gene expression in 10T1/2 mesenchymal cells or BALB/c-3T3 fibroblasts. These results suggest that Sox9 is a general transcriptional regulator of cartilage-specific genes. However, Sox9 does not appear to be able to induce the chondrocyte phenotype in nonchondrogenic cells, implying that other factors are involved in chondrogenesis.
转录因子Sox9能够增强II型胶原蛋白基因的表达，并且可能在软骨形成过程中发挥关键作用。为了确定Sox9是否是软骨细胞表型的诱导因子，我们研究了Sox9在另一个编码软骨衍生视黄酸敏感蛋白（CD-RAP）的软骨基因转录中的作用。CD-RAP在软骨形成过程中特异性表达。我们在此表明，Sox9蛋白能够结合CD-RAP启动子中的SOX共有序列。SOX基序的突变导致软骨细胞中CD-RAP启动子构建体的转录减少。SOX9的过表达导致软骨细胞和非软骨形成细胞中CD-RAP启动子驱动的报告基因活性呈剂量依赖性增加。一种截短的SOX9，其包含一个结合结构域但没有反式激活功能，抑制了CD-RAP启动子活性。SOX9的过表达增加了软骨细胞中内源性CD-RAP mRNA的水平，但不能在10T1/2间充质细胞或BALB/c-3T3成纤维细胞中诱导内源性基因表达。这些结果表明，Sox9是软骨特异性基因的一般转录调节因子。然而，Sox9似乎不能在非软骨形成细胞中诱导软骨细胞表型，这意味着软骨形成过程涉及其他因素。
