Hirose Y, Manley J L
Department of Biological Sciences, Columbia University, New York, New York 10027, USA.
Nature. 1998 Sep 3;395(6697):93-6. doi: 10.1038/25786.
Production of messenger RNA in eukaryotic cells is a complex, multistep process. mRNA polyadenylation, or 3' processing, requires several protein factors, including cleavage/polyadenylation-specificity factor (CPSF), cleavage-stimulation factor, two cleavage factors and poly(A) polymerase. These proteins seem to be unnecessary for other steps in mRNA synthesis such as transcription and splicing, and factors required for these processes were not considered to be essential for polyadenylation. Nonetheless, these reactions may be linked so that they are effectively coordinated in vivo. For example, the CTD carboxy-terminal domain of the largest subunit of RNA polymerase II (RNAP II) is required for efficient splicing and polyadenylation in vivo, and CPSF is brought to a promoter by the transcription factor TFIID and transferred to RNAP II at the time of transcription initiation. These findings suggest that polyadenylation factors can be recruited to an RNA 3'-processing signal by RNAP II, where they dissociate from the polymerase and initiate polyadenylation. Here we present results that extend this model by showing that RNAP II is actually required, in the absence of transcription, for 3' processing in vitro.
真核细胞中信使核糖核酸（mRNA）的产生是一个复杂的多步骤过程。mRNA的聚腺苷酸化，即3' 加工，需要几种蛋白质因子，包括切割/聚腺苷酸化特异性因子（CPSF）、切割刺激因子、两种切割因子和聚腺苷酸聚合酶。这些蛋白质对于mRNA合成的其他步骤，如转录和剪接，似乎并非必需，并且这些过程所需的因子也不被认为对聚腺苷酸化至关重要。尽管如此，这些反应可能相互关联，从而在体内有效地协调进行。例如，RNA聚合酶II（RNAP II）最大亚基的CTD羧基末端结构域对于体内有效的剪接和聚腺苷酸化是必需的，并且CPSF由转录因子TFIID带到启动子处，并在转录起始时转移到RNAP II上。这些发现表明，聚腺苷酸化因子可以被RNAP II招募到RNA 3' 加工信号处，在那里它们从聚合酶上解离并启动聚腺苷酸化。在这里，我们展示的结果扩展了这个模型，表明在体外无转录的情况下，3' 加工实际上需要RNAP II。
