RNA Polymerase II Transcription

RNA polymerase II (Pol II) is the central enzyme that catalyses DNA- directed mRNA synthesis during the transcription of protein-coding genes. Pol II consists of a 10-subunit catalytic core, which alone is capable of elongating the RNA transcript, and a complex of two subunits, Rpb4/7, that is required for transcription initiation. <BR> The transcription cycle is divided in three major phases: initiation, elongation, and termination. Transcription initiation include promoter DNA binding, DNA melting, and initial synthesis of short RNA transcripts. The transition from initiation to elongation, is referred to as promoter escape and leads to a stable elongation complex that is characterized by an open DNA region or transcription bubble. The bubble contains the DNA-RNA hybrid, a heteroduplex of eight to nine base pairs. The growing 3-end of the RNA is engaged with the polymerase complex active site. Ultimately transcription terminates and Pol II dissocitates from the template.

RNA 聚合酶II（Pol II）是催化蛋白质编码基因转录过程中DNA指导的mRNA合成的核心酶。Pol II由一个由10个亚单位组成的催化核心组成，该核心本身即能够延长RNA转录本，并包含一个由两个亚单位Rpb4/7组成的复合体，该复合体对于转录起始至关重要。转录周期可分为三个主要阶段：启动、延长和终止。转录启动包括启动子DNA结合、DNA解链以及短RNA转录本的初始合成。从启动到延长的过渡被称为启动子逃逸，并导致形成一种稳定的延长复合体，其特征为开放的DNA区域或转录泡。该泡内含有DNA-RNA杂合体，一个由八个至九个碱基对组成的杂合双链。RNA的延伸3'端与聚合酶复合体的活性位点结合。最终，转录终止，Pol II从模板上解离。