The genetics of ribosomal reading frame maintenance

描述(由申请人提供)：由 核糖体通常是一个忠实的过程，但也会出现错误。MRNAs中的序列 已经进化到调整翻译的准确性以增加 平移框架错误的频率。这样的地点被称为 程序化的翻译移码站点。酵母菌Ty Elements，一类 逆转录转座子，表达逆转录转座所需的酶。 编程+1移帧机制。我们发现了移帧的证据 发生是因为mRNA干扰了核糖体精确中心的功能 通过将肽-tRNAs插入核糖体P位点，使非典型性 与信使核糖核酸相互作用。不寻常的密码子*反密码子复合体形成的破坏 核糖体准确识别框内同源tRNA的能力 A站点。此外，来自Ty3反转录转座子的序列似乎 直接与rRNA中的结构相互作用，这是准确解码所必需的 在A站点。这个序列被称为Ty3刺激子，似乎是碱基对 与螺旋18环的一部分。该碱基配对区域中的核苷酸， G530，直接接触A位点的mRNA和tRNA核苷酸 密码子*反密码子复合体，确保它们正确配对。通过 将核苷酸隔离在rnRNA*rRNA复合体中，Ty3刺激器可以 减少A站点的总体歧视。最近，详细的分子 解决了30s、50s和70s核糖体的结构。这些结构 提供了关于核糖体结构的前所未有的详细程度， 并可用于预测翻译过程中使用的机制，包括 纠错机制。这些结构清楚地显示出同源关系， 框内tRNA可被识别，但几乎不提供有关如何识别的直接信息 核糖体避免了导致翻译框架改变的错误。可以说， 框架的维持是核糖体最关键的作用，因为框架 错误几乎总是导致非活性蛋白质产品的生产，而 误判错误很少发生。为了解决核糖体如何维持阅读框架的问题 我们一直在使用编程的翻译提供的工具 移框站点。我们将继续这项工作，试图确定如何 核糖体的纠错元件在这一过程中发挥作用。最近， 我们发现，刺激帧错误的mRNA序列也会导致错误 在翻译启蒙过程中。这表明这些数据的准确性 流程有共同的方面。我们将使用由提供的孪生工具 分析核糖体功能的移码和翻译起始 确保准确性。

DESCRIPTION (provided by applicant): Translation of mRNA sequences by the ribosome is normally a faithful process, yet mistakes occur. Sequences in mRNAs have evolved that modulate the accuracy of translation to increase the frequency of translational frameshifting errors. Such sites are termed programmed translational frameshift sites. The yeast Ty elements, a class of retrotransposons, express the enzymes needed for retrotransposition using a programmed+1 frameshifting mechanism. We find evidence that frameshifting occurs because the mRNA disrupts the function of the ribosomal accuracy center by inserting peptidyl-tRNAs into the ribosomal P site that Make a non-canonical interaction with the mRNA. The unusual codon*anticodon complex formed disrupts the ability of the ribosome to accurately recognize in-frame cognate tRNAs in the A site. Also, a sequence derived from the Ty3 retrotransposon appears to directly interact with a structure in the rRNA necessary for accurate decoding in the A site. This sequence, termed the Ty3 stimulator, appears to base pair with part of the loop of Helix 18. A nucleotide in that base paired region, G530, directly contacts both mRNA and tRNA nucleotides in the A site codon*anticodon complex to assure that they are correctly paired. By sequestering that nucleotide in an rnRNA*rRNA complex, the Ty3 stimulator could reduce overall discrimination in the A site. Recently, detailed molecular structures of the 30S, 50S and 70S ribosomes were solved. These structures provide an unprecedented level of detail about the structure of the ribosome, and can be used to predict the mechanisms used during translation, including the error correction mechanisms. The structures clearly show how cognate, in-frame tRNAs are recognized, but gives little direct information about how the ribosome avoids errors leading to changes in translational frame. Arguably, maintenance of frame is the most critical role for the ribosome, since frame errors almost always result in production of inactive protein products while missense errors rarely do. To address how the ribosome maintains reading frame we have been using the tools provided by the programmed translational frameshift sites. We will continue that work attempting to determine how error-correcting elements of the ribosome function in this process. Recently, we found that mRNA sequences that stimulate frame errors also induce errors during translational initiation. This suggests that the accuracy of these processes has shared aspects. We will use the twin tools afforded by frameshifting and translation initiation to dissect the ribosomal functions insuring accuracy.