Transcription Through Nucleosomes by RNA Polymerase II

真核细胞核内的DNA被包装成染色质--一种由称为核小体的重复单位组成的紧密的核蛋白复合物。Pol II已经开发出一种特殊的机制来转录这种紧密包装的DNA。本项目旨在研究酵母Pol II延伸复合物通过独特定位的核小体核心的体外转录。我们应用最近开发的实验系统，采用正宗Pol II延伸复合物的组装和这些复合物在体外的单核细胞的连接。已经发现，该系统忠实地概括了启动子依赖性实验系统的主要性质，如转录核小体屏障的高度和一般性质。我们证明了Pol II使用独特的机制通过染色质进行转录。该机制的令人惊讶的标志是聚合酶通过核小体转录的能力，而在所有其他分析的RNA聚合酶的情况下观察到核小体位置没有伴随变化。

The DNA within the eukaryotic nucleus is packaged as chromatin - a tight nucleoprotein complex composed of repeating units called nucleosomes. Pol II has developed a special mechanism to transcribe through such a tightly packed DNA. This project is aimed to investigate transcription by yeast Pol II elongation complexes through uniquely positioned nucleosome core in vitro. We apply recently developed experimental system employing assembly of authentic Pol II elongation complexes and ligation of these complexes to the mononucleosome in vitro. It has been found that this system faithfully recapitulates chief properties of the promoter-dependent experimental system such as the height and general properties of the nucleosomal barrier to transcription. We demonstrate that Pol II uses unique mechanism for transcription through chromatin. Surprising landmark of this mechanism is ability of the polymerase to transcribe through the nucleosome without accompanying change in nucleosome position observed in the case of all other analyzed RNA polymerases.