The genetics of ribosomal reading frame maintenance

描述（由申请人提供）： 核糖体在正常情况下是一个忠实的过程，但也会发生错误。mRNA序列 已经进化到调节翻译的准确性， 翻译移码错误的频率。这些网站被称为 程序化翻译移码位点。酵母Ty元件是一类 逆转录转座子，表达逆转录转座所需的酶， 程序化+1移码机制。我们发现有证据表明 因为mRNA破坏了核糖体精确中心的功能 通过将肽基-tRNA插入核糖体P位点， 与mRNA的相互作用。不寻常的密码子 * 反密码子复合体的形成破坏了 核糖体准确识别框内同源tRNA的能力， A网站此外，来自Ty 3反转录转座子的序列似乎 直接与精确解码所需的rRNA结构相互作用 在A网站该序列被称为Ty 3刺激物，似乎是碱基配对的 与H18的环的一部分。在碱基配对区域的核苷酸， G530直接接触A位点的mRNA和tRNA核苷酸 密码子 * 反密码子复合物，以确保它们正确配对。通过 Ty 3刺激剂将核苷酸隔离在rRNA *rRNA复合物中， 降低A位点的总体歧视。最近，详细的分子 解析了30 S、50 S和70 S核糖体的结构。这些结构 提供了前所未有的关于核糖体结构的细节， 并可用于预测翻译过程中使用的机制，包括 错误纠正机制。这些结构清楚地表明了同源性 框内tRNA被识别，但很少提供关于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， 维持框架是核糖体最关键的作用，因为框架 错误几乎总是导致产生无活性的蛋白质产物， 而误判则很少发生。为了解决核糖体如何维持阅读框架 我们一直在使用由编程翻译提供的工具， 移码点我们将继续这项工作， 核糖体的纠错元件在这个过程中发挥作用。最近， 我们发现，刺激框架错误的mRNA序列也会诱发错误， 在翻译起始阶段。这表明，这些数据的准确性 过程具有共享的方面。我们将使用两种工具， 移码和翻译起始来剖析核糖体功能 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.