生物谷报道：科学家们亲眼目睹了活组织中的基因转录过程，这一最新的研究成果在线发表在8月号的《自然—结构和分子生物学》期刊上。
RNA聚合酶II是一种将DNA信息转录到信使RNA的酶，由这种酶所实施的转录是基因表达的核心，也是生物调控机制的关键所在。以前，绝大部分对这种转录过程的了解来自于用纯化物质在生物体外所做的试管实验，科学家们对RNA聚合酶在活体中的作用过程知之甚少。
利用高级荧光成像技术，Robert Singer和合作者量化测量了RNA聚合酶在活哺乳类动物细胞中实施遗传转录的动力学过程，从而将更高级生物中的基因转录机理分析提高到了一个新水平。这项工作的最终目标是建立活体中基因转录的量化模型。在活体组织的转录中，他们发现了全新和意料之外的特征。
首先，他们认为只有大约1%的与基因相连结的RNA聚合酶参加了基因转录过程，并产生出信使RNA。其次，他们发现RNA聚合酶转录的速度比想象的更快，而且通常只是在周期延长时才暂时停止。
在量化认识单个活体细胞中的转录机理过程中，该新研究是一个里程碑性的贡献。（科学时报）
原始出处:
Nature Structural & Molecularbiology
Published online: 5 August 2007; | doi:10.1038/nsmb1280
In vivo dynamics of RNA polymerase II transcription
Xavier Darzacq1, 2, Yaron Shav-Tal1, 3, Valeria de Turris1, Yehuda Brody3, Shailesh M Shenoy1, Robert D Phair4 & Robert H Singer1
1 Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
2 Laboratoire de Génétique Moléculaire, Centre National de la Recherche Scientifique, UMR-8541, Ecole Normale Supérieure, 75005 Paris, France.
3 The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan 52900, Israel.
4 Integrative Bioinformatics, Inc., Los Altos, California 94024, USA.
Correspondence should be addressed to Robert H Singer rhsinger@aecom.yu.edu
We imaged transcription in living cells using a locus-specific reporter system, which allowed precise, single-cell kinetic measurements of promoter binding, initiation and elongation. Photobleaching of fluorescent RNA polymerase II revealed several kinetically distinct populations of the enzyme interacting with a specific gene. Photobleaching and photoactivation of fluorescent MS2 proteins used to label nascent messenger RNAs provided sensitive elongation measurements. A mechanistic kinetic model that fits our data was validated using specific inhibitors. Polymerases elongated at 4.3 kilobases min-1, much faster than previously documented, and entered a paused state for unexpectedly long times. Transcription onset was inefficient, with only 1% of polymerase-gene interactions leading to completion of an mRNA. Our systems approach, quantifying both polymerase and mRNA kinetics on a defined DNA template in vivo with high temporal resolution, opens new avenues for studying regulation of transcriptional processes in vivo.
