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首页> 美国卫生研究院文献>Proceedings of the National Academy of Sciences of the United States of America >The initiation–elongation transition: Lateral mobility of RNA in RNA polymerase II complexes is greatly reduced at +8/+9 and absent by +23
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The initiation–elongation transition: Lateral mobility of RNA in RNA polymerase II complexes is greatly reduced at +8/+9 and absent by +23

机译：起始-延伸过渡：RNA聚合酶II复合物中RNA的侧向迁移率在+ 8 / + 9时大大降低而在+23时不存在

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摘要

RNA polymerase II transcription complexes stalled shortly after initiation over a repetitive segment of the template can undergo efficient transcript slippage, during which the 3′ end of the RNA slides upstream and then re-pairs with the template, allowing transcription to continue. In the present study, we have used transcript slippage as an assay to identify possible structural transitions that occur as the polymerase passes from the initiation to the elongation phase of transcription. We reasoned that transcript slippage would not occur in fully processive complexes. We constructed a series of templates that allowed us to stall RNA polymerase II after the synthesis of a repetitive sequence (5′-CUCUCU-3′) at varying distances downstream of +1. We found that polymerase must synthesize at least a 23-nt RNA to attain resistance to transcript slippage. The ability to undergo slippage was lost in two discrete steps, suggestive of two distinct transitions. The first transition is the formation of the 8- to 9-bp mature RNA–DNA hybrid, when slippage abruptly dropped by 10-fold. However, easily detectable slippage continued until 14 more bonds were made. Thus, although the transcript becomes tightly constrained within the transcription complex once the hybrid reaches its final length, much more RNA synthesis is required before the RNA is no longer able to slip upstream along the template. This last point may reflect an important stabilizing role for the interaction of the polymerase with the transcript well upstream of the RNA–DNA hybrid.
机译：在模板的重复片段上起始后不久停滞的RNA聚合酶II转录复合物可以进行有效的转录滑动，在此过程中，RNA的3'端向上游滑动，然后与模板重新配对，使转录继续进行。在本研究中，我们已使用转录本滑动作为一种检测方法，以识别随着聚合酶从转录起始阶段到延伸阶段而发生的可能的结构转变。我们认为在完全进行的复合体中不会出现转录本滑动。我们构建了一系列模板，这些模板使我们能够在+1下游不同距离的重复序列（5'-CUCUCU-3'）合成后停止RNA聚合酶II。我们发现聚合酶必须合成至少一个23 nt的RNA，以获得对转录滑动的抗性。滑移的能力在两个不连续的步骤中消失了，暗示了两个不同的过渡。第一个转变是当滑移突然下降10倍时，形成8至9 bp的成熟RNA-DNA杂种。但是，易于检测到的滑移一直持续到再进行14次粘结为止。因此，尽管一旦杂交体达到其最终长度，转录物就被紧密地限制在​​转录复合物中，但是在RNA不再能够沿着模板向上游滑动之前，需要更多的RNA合成。最后一点可能反映了聚合酶与RNA-DNA杂交上游的转录本相互作用的重要稳定作用。

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