Kasamatsu Shinya, Sato Ayuko, Yamamoto Taichi, Keng Vincent W, Yoshida Hiroshi, Yamazaki Yuka, Shimoda Masafumi, Miyazaki Jun-ichi, Noguchi Tamio
Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya 464-8601.
J Biochem. 2004 Feb;135(2):217-23. doi: 10.1093/jb/mvh025.
The homeodomain-containing protein Hex acts as an activator as well as a repressor of transcription in animals. While its repression domain has been mapped to the amino-terminal region, the activation domain has never been identified. Here, we show that the homeodomain and the acidic carboxyl-terminal region are necessary for full activation of the sodium-dependent bile acid cotransporter gene promoter in a cell type-independent manner, suggesting that the carboxyl-terminal region comprising residues 197 to 271 functions as the activation domain. In addition, we observed that a Hex mutant without this activation domain acts as a dominant-negative mutant as to the transactivating function of Hex.
含同源结构域的蛋白质Hex在动物体内既作为转录激活因子又作为转录抑制因子发挥作用。虽然其抑制结构域已定位到氨基末端区域，但激活结构域从未被确定。在此，我们表明，同源结构域和酸性羧基末端区域以细胞类型非依赖性方式对钠依赖性胆汁酸共转运蛋白基因启动子的完全激活是必需的，这表明包含第197至271位残基的羧基末端区域作为激活结构域发挥作用。此外，我们观察到，没有这个激活结构域的Hex突变体对Hex的反式激活功能起到显性负性突变体的作用。
