Howard Hughes Medical Institute, Department of Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA.
Mol Cell. 2013 Aug 22;51(4):480-92. doi: 10.1016/j.molcel.2013.08.009.
To bridge the gap between in vivo and in vitro molecular mechanisms, we dissected the transcriptional control of the endogenous histone gene cluster (His-C) by single-cell imaging. A combination of quantitative immunofluorescence, RNA FISH, and FRAP measurements revealed atypical promoter recognition complexes and differential transcription kinetics directing histone H1 versus core histone gene expression. While H1 is transcribed throughout S phase, core histones are only transcribed in a short pulse during early S phase. Surprisingly, no TFIIB or TFIID was detectable or functionally required at the initiation complexes of these promoters. Instead, a highly stable, preloaded TBP/TFIIA "pioneer" complex primes the rapid initiation of His-C transcription during early S phase. These results provide mechanistic insights for the role of gene-specific core promoter factors and implications for cell cycle-regulated gene expression.
为了弥合体内和体外分子机制之间的差距，我们通过单细胞成像技术对内源性组蛋白基因簇（His-C）的转录调控进行了剖析。定量免疫荧光、RNA FISH 和 FRAP 测量的组合揭示了非典型的启动子识别复合物和不同的转录动力学，分别指导组蛋白 H1 和核心组蛋白基因的表达。虽然 H1 在整个 S 期都被转录，但核心组蛋白仅在 S 期早期的短暂脉冲中被转录。令人惊讶的是，在这些启动子的起始复合物中，无法检测到 TFIIB 或 TFIID，或者它们在功能上是必需的。相反，高度稳定的、预先加载的 TBP/TFIIA“先驱”复合物在 S 期早期快速启动 His-C 转录。这些结果为基因特异性核心启动子因子的作用提供了机制上的见解，并对细胞周期调控基因表达具有重要意义。
