Polly Patsie, Haddadi Leila M, Issa Laura L, Subramaniam Nanthakumar, Palmer Stephen J, Tay Enoch S E, Hardeman Edna C
Muscle Development Unit, Children's Medical Research Institute, Wentworthville, New South Wales 2145, Australia.
J Biol Chem. 2003 Sep 19;278(38):36603-10. doi: 10.1074/jbc.M212814200. Epub 2003 Jul 10.
The novel transcription factor hMusTRD1alpha1 (human muscle TFII-I repeat domain-containing protein 1alpha1; previously named MusTRD1; O'Mahoney, J. V., Guven, K. L., Lin, J., Joya, J. E., Robinson, C. S., Wade, R. P., and Hardeman, E. C. (1998) Mol. Cell. Biol. 18, 6641-6652) was identified in a yeast one-hybrid screen as a protein that binds within an upstream enhancer-containing region of the skeletal muscle-specific gene, TNNI1 (human troponin I slow; hTnIslow). It has been proposed that hMusTRD1alpha1 may play an important role in fiber-specific muscle gene expression by virtue of its ability to bind to an Inr-like element (nucleotides -977 to -960) within the hTnIslow upstream enhancer-containing region that is necessary for slow fiber-specific expression. In this study we demonstrate that both MEF2C, a known regulator of slow fiber-specific genes, and hMusTRD1alpha1 regulate hTnIslow through the Inr-like element. Co-transfection assays in C2C12 cells and Cos-7 cells demonstrate that hMusTRD1alpha1 represses hTnIslow transcription and prevents MEF2C-mediated activation of hTnIslow transcription. Gel shift analysis shows that hMusTRD1alpha1 can abrogate MEF2C binding to its cognate site in the hTnIslow enhancer. Glutathione S-transferase pull-down assays demonstrate that hMusTRD1alpha1 can interact with both MEF2C and the nuclear receptor co-repressor. The data support the role of hMusTRD1alpha1 as a repressor of slow fiber-specific transcription through mechanisms involving direct interactions with MEF2C and the nuclear receptor co-repressor.
新型转录因子hMusTRD1alpha1（人类肌肉含TFII-I重复结构域蛋白1alpha1；先前称为MusTRD1；奥马奥尼，J.V.，古文，K.L.，林，J.，乔亚，J.E.，罗宾逊，C.S.，韦德，R.P.，哈迪曼，E.C.（1998年）《分子与细胞生物学》18卷，6641 - 6652页）在酵母单杂交筛选中被鉴定为一种能结合骨骼肌特异性基因TNNI1（人类肌钙蛋白I慢型；hTnIslow）上游含增强子区域的蛋白质。有人提出，hMusTRD1alpha1可能因其能够结合hTnIslow上游含增强子区域内的一个类起始子元件（核苷酸 - 977至 - 960）而在纤维特异性肌肉基因表达中发挥重要作用，该元件是慢纤维特异性表达所必需的。在本研究中，我们证明了慢纤维特异性基因的已知调节因子MEF2C和hMusTRD1alpha1都通过类起始子元件调节hTnIslow。在C2C12细胞和Cos - 7细胞中的共转染实验表明，hMusTRD1alpha1抑制hTnIslow转录，并阻止MEF2C介导的hTnIslow转录激活。凝胶迁移分析表明，hMusTRD1alpha1可以消除MEF2C与其在hTnIslow增强子中的同源位点的结合。谷胱甘肽S - 转移酶下拉实验表明，hMusTRD1alpha1可以与MEF2C和核受体共抑制因子相互作用。这些数据支持hMusTRD1alpha1作为慢纤维特异性转录抑制因子的作用，其机制涉及与MEF2C和核受体共抑制因子的直接相互作用。
