Transcription Through Nucleosomes by RNA Polymerase II

真核生物细胞核内的DNA被包装成染色质，染色质是一种紧密的核蛋白复合物，由称为核小体的重复单位组成。Pol II已经发展出一种特殊的机制来转录这种紧密排列的DNA。本项目旨在通过独特定位的核小体核心研究酵母Pol II延伸复合物的体外转录。我们应用最近开发的实验系统，采用组装真正的Pol II延伸复合物和这些复合物连接到体外的单核小体。研究发现，该系统忠实地概括了启动子依赖性实验系统的主要特性，如核小体转录屏障的高度和一般特性。我们证明了Pol II通过染色质进行转录的独特机制。该机制令人惊讶的里程碑是聚合酶能够通过核小体转录而不伴随核小体位置的变化，这在所有其他分析的RNA聚合酶的情况下都观察到。

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.