Department of Biology, Faculty of Education and Integrated Arts and Sciences, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan.
Biochemistry. 2010 Mar 23;49(11):2351-8. doi: 10.1021/bi901950w.
Superhelically curved DNA structures can strongly activate transcription in mammalian cells. However, the mechanism underlying the activation has not been clarified. We investigated this mechanism in yeast cells, using 108, 180, and 252 bp synthetic curved DNA segments. Even in the presence of nucleosomes, these DNAs activated transcription from a UAS-deleted CYC1 promoter that is silenced in the presence of nucleosomes. The fold-activations of transcription by these segments, relative to the transcription on the control that lacked such segments, were 51.4, 63.4, and 56.4, respectively. The superhelically curved DNA structures favored nucleosome formation. However, the translational positions of the nucleosomes were dynamic. The high mobility of the nucleosomes on the superhelically curved DNA structures seemed to influence the mobility of the nucleosomes formed on the promoter and eventually enhanced the access to the center region of one TATA sequence. Functioning as a dock for the histone core and allowing nucleosome sliding seem to be the mechanisms underlying the transcriptional activation by superhelically curved DNA structures in chromatin. The present study provides important clues for designing and constructing artificial chromatin modulators, as a tool for chromatin engineering.
超螺旋弯曲的 DNA 结构可以在哺乳动物细胞中强烈激活转录。然而，其激活的机制尚未阐明。我们使用 108、180 和 252 个碱基对的合成弯曲 DNA 片段，在酵母细胞中研究了这一机制。即使存在核小体，这些 DNA 也能激活转录，其启动子上的 UAS 缺失，在存在核小体时被沉默。这些片段相对于缺乏这些片段的对照转录的转录折叠激活分别为 51.4、63.4 和 56.4。超螺旋弯曲的 DNA 结构有利于核小体的形成。然而，核小体的翻译位置是动态的。核小体在超螺旋弯曲的 DNA 结构上的高迁移率似乎影响了在启动子上形成的核小体的迁移率，并最终增强了对一个 TATA 序列中心区域的接近。作为组蛋白核心的停靠点并允许核小体滑动似乎是超螺旋弯曲的 DNA 结构在染色质中激活转录的机制。本研究为设计和构建人工染色质调节剂提供了重要线索，作为染色质工程的工具。
