Doctoral Program of Sports Medicine, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan.
Biochem Biophys Res Commun. 2013 Jan 11;430(2):664-9. doi: 10.1016/j.bbrc.2012.11.094. Epub 2012 Dec 2.
Transcription factor E3 (TFE3) belongs to a basic helix-loop-helix family, and is involved in the biology of osteoclasts, melanocytes and their malignancies. We previously reported the metabolic effects of TFE3 on insulin in the liver and skeletal muscles in animal models. In the present study, we explored a novel role for TFE3 in a skeletal muscle cell line. When TFE3 was overexpressed in C2C12 myoblasts by adenovirus before induction of differentiation, myogenic differentiation of C2C12 cells was significantly inhibited. Adenovirus-mediated TFE3 overexpression also suppressed the gene expression of muscle regulatory factors (MRFs), such as MyoD and myogenin, during C2C12 differentiation. In contrast, knockdown of TFE3 using adenovirus encoding short-hairpin RNAi specific for TFE3 dramatically promoted myoblast differentiation associated with significantly increased expression of MRFs. Consistent with these findings, promoter analyses via luciferase reporter assay and electrophoretic mobility shift assay suggested that TFE3 negatively regulated myogenin promoter activity by direct binding to an E-box, E2, in the myogenin promoter. These findings indicated that TFE3 has a regulatory role in myoblast differentiation, and that transcriptional suppression of myogenin expression may be part of the mechanism of action.
转录因子 E3（TFE3）属于碱性螺旋-环-螺旋家族，参与破骨细胞、黑素细胞及其恶性肿瘤的生物学过程。我们之前在动物模型中报道了 TFE3 对肝脏和骨骼肌中胰岛素的代谢作用。在本研究中，我们在骨骼肌细胞系中探索了 TFE3 的一个新作用。在诱导分化之前，通过腺病毒过表达 TFE3 可显著抑制 C2C12 成肌细胞的成肌分化。腺病毒介导的 TFE3 过表达也抑制了 C2C12 分化过程中肌肉调节因子（MRFs）如 MyoD 和 myogenin 的基因表达。相比之下，用针对 TFE3 的短发夹 RNAi 的腺病毒敲低 TFE3 可显著促进成肌细胞分化，同时显著增加 MRFs 的表达。与这些发现一致，通过荧光素酶报告基因分析和电泳迁移率变动分析表明，TFE3 通过直接结合肌生成素启动子中的 E 盒 E2 负调控肌生成素启动子活性。这些发现表明 TFE3 在成肌细胞分化中具有调节作用，而肌生成素表达的转录抑制可能是其作用机制的一部分。
