Transcription Through Nucleosomes by RNA Polymerase II

真核细胞核内的DNA被包装成染色质--一种紧密的核蛋白复合体，由称为核小体的重复单位组成。POL II已经开发出一种特殊的机制，可以通过如此紧密的DNA转录。本项目旨在研究酵母Pol II伸长复合体通过独特定位的核小体核心在体外转录。我们应用最近开发的实验系统，通过组装真正的Pol II延伸复合体并将这些复合体连接到体外的单核小体上。已经发现，该系统忠实地概括了依赖启动子的实验系统的主要性质，如核小体转录障碍的高度和一般性质。我们证明POL II通过染色质使用独特的转录机制。这一机制的令人惊讶的里程碑是聚合酶能够通过核小体转录，而不会伴随着在所有其他分析的RNA聚合酶中观察到的核小体位置的变化。

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.