Oda Tsukasa, Fukuda Aya, Hagiwara Hiroko, Masuho Yasuhiko, Muramatsu Masa-Aki, Hisatake Koji, Yamashita Takayuki
Division of Genetic Diagnosis, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
J Cell Biochem. 2004 Nov 1;93(4):788-806. doi: 10.1002/jcb.20114.
Various TATA-binding protein (TBP)-associated proteins are involved in the regulation of gene expression through control of basal transcription directed by RNA polymerase (Pol) II. We recently identified a novel nuclear protein, activator of basal transcription 1 (ABT1), which binds TBP and DNA, and enhances Pol II-directed basal transcription. To better understand regulatory mechanisms for ABT1, we searched for ABT1-binding proteins using a yeast two-hybrid screening and isolated a cDNA clone encoding a novel protein termed ABT1-associated protein (ABTAP). ABTAP formed a complex with ABT1 and suppressed the ABT1-induced activation of Pol II-directed transcription in mammalian cells. Furthermore, ABTAP directly bound to ABT1, disrupted the interaction between ABT1 and TBP, and suppressed the ABT1-induced activation of Pol II-directed basal transcription in vitro. These two proteins colocalized in the nucleolus and nucleoplasm and were concomitantly relocalized into discrete nuclear bodies at higher expression of ABTAP. Taken together, these results suggest that ABTAP binds and negatively regulates ABT1. The ABT1/ABTAP complex is evolutionarily conserved and may constitute a novel regulatory system for basal transcription.
多种TATA结合蛋白（TBP）相关蛋白通过控制RNA聚合酶（Pol）II介导的基础转录参与基因表达调控。我们最近鉴定出一种新型核蛋白，基础转录激活因子1（ABT1），它能结合TBP和DNA，并增强Pol II介导的基础转录。为了更好地理解ABT1的调控机制，我们利用酵母双杂交筛选寻找ABT1结合蛋白，并分离出一个编码新型蛋白ABT1相关蛋白（ABTAP）的cDNA克隆。ABTAP与ABT1形成复合物，并在哺乳动物细胞中抑制ABT1诱导的Pol II介导转录的激活。此外，ABTAP直接与ABT1结合，破坏ABT1与TBP之间的相互作用，并在体外抑制ABT1诱导的Pol II介导的基础转录激活。这两种蛋白在核仁和核质中共定位，并在ABTAP高表达时同时重新定位到离散的核体中。综上所述，这些结果表明ABTAP结合并负向调节ABT1。ABT1/ABTAP复合物在进化上是保守的，可能构成基础转录的一种新型调控系统。
