Saito Taku, Ikeda Toshiyuki, Nakamura Kozo, Chung Ung-il, Kawaguchi Hiroshi
Department of Sensory and Motor System Medicine, Faculty of Medicine, Center for Disease Biology and Integrative Medicine, University of Tokyo, Hongo 7-3-1, Bunkyo, Tokyo 113-8655, Japan.
EMBO Rep. 2007 May;8(5):504-9. doi: 10.1038/sj.embor.7400934. Epub 2007 Mar 30.
Transcription factor SOX9 (sex-determining region Y-type high mobility group box 9) and its coactivators SOX5 and SOX6 (the SOX trio) induce early-stage chondrocyte differentiation and suppress its terminal stage. To identify possible targets of the SOX trio, we carried out a microarray analysis and identified S100A1 and S100B as possible target molecules. S100 protein expression was localized in late proliferative and pre-hypertrophic chondrocytes of the mouse growth plate. Overexpression of S100A1, S100B or their combination in cultured chondrogenic cells did not induce early differentiation, but suppressed hypertrophic differentiation and mineralization. Silencing of both S100A1 and S100B stimulated terminal differentiation and reversed the SOX-trio-mediated inhibition. Finally, luciferase reporter, electrophoretic mobility shift and chromatin immunoprecipitation analyses showed that transcription of both S100 proteins is induced by the SOX trio, and also identified their respective enhancer elements in the 5'-end flanking region. We conclude that S100A1 and S100B are transcriptional targets of the SOX trio and mediate its inhibition of terminal differentiation of chondrocytes.
转录因子SOX9（性别决定区Y型高迁移率族蛋白9）及其共激活因子SOX5和SOX6（SOX三联体）诱导软骨细胞早期分化并抑制其终末阶段。为了确定SOX三联体可能的靶标，我们进行了微阵列分析，并确定S100A1和S100B为可能的靶分子。S100蛋白表达定位于小鼠生长板的晚期增殖性软骨细胞和前肥大软骨细胞。在培养的软骨生成细胞中过表达S100A1、S100B或它们的组合不会诱导早期分化，但会抑制肥大分化和矿化。沉默S100A1和S100B均会刺激终末分化并逆转SOX三联体介导的抑制作用。最后，荧光素酶报告基因、电泳迁移率变动和染色质免疫沉淀分析表明，两种S100蛋白的转录均由SOX三联体诱导，并且还在5'端侧翼区域鉴定了它们各自的增强子元件。我们得出结论，S100A1和S100B是SOX三联体的转录靶标，并介导其对软骨细胞终末分化的抑制作用。
