Curran J F, Yarus M
Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder 80309.
J Mol Biol. 1988 Sep 5;203(1):75-83. doi: 10.1016/0022-2836(88)90092-7.
It has been suggested that Escherichia coli release factor 2 (RF-2) translation is autoregulated. Mature RF-2 protein can terminate its own nascent synthesis at an intragenic, in-phase UGA codon, or alternatively, a +1 frameshift can occur that leads to completion of the RF-2 polypeptide. Translational termination presumably increases with RF-2 concentration, providing negative regulatory feedback. We now show, in lacZ/RF-2 fusions, that translation of a UAG codon at the position of the UGA competes with frameshifting, which proves one postulate of the translational autoregulatory model. We also identify a nearby sequence that is required for high-frequency frameshifting and suggest a constraint for the codon preceding the shift point. Both these sequences are incorporated into a model for frameshifting. Our measurements allow us to compute the relative rates in vivo of these reactions: release factor action, frameshifting and tRNA selection at an amber codon.
有人提出，大肠杆菌释放因子2（RF-2）的翻译是自动调节的。成熟的RF-2蛋白可以在基因内的同相位UGA密码子处终止其自身的新生合成，或者，也可能发生+1移码，从而导致RF-2多肽的合成完成。翻译终止可能会随着RF-2浓度的增加而增加，从而提供负调控反馈。我们现在在lacZ/RF-2融合体中表明，UGA位置的UAG密码子的翻译与移码相互竞争，这证明了翻译自动调节模型的一个假设。我们还鉴定出一个高频移码所需的附近序列，并提出了对移码点之前密码子的限制。这两个序列都被纳入了一个移码模型。我们的测量使我们能够计算出这些反应在体内的相对速率：释放因子的作用、移码以及在琥珀密码子处的tRNA选择。
