Dynamics and processivity of 40S ribosome scanning on mRNA in yeast
Dynamics and processivity of 40S ribosome scanning on mRNA in yeast
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DOI：
10.1046/j.1365-2958.2003.03898.x
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发表时间：
2004-02-01
影响因子：
3.6
通讯作者：
McCarthy, JEG
中科院分区：
文献类型：
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作者：
Berthelot, K;Muldoon, M;McCarthy, JEG
真核40 S核糖体亚基通过所谓的扫描过程定位mRNA上的翻译起始密码子，该过程在40 S结合到加帽的5'端之后。翻译中的这一关键步骤是几乎所有真核基因表达所必需的，但扫描的机制和动力学尚不清楚。我们在体内和体外对酵母40 S核糖体沿着不同长度的5'非翻译区（UTR）的运动进行了定量研究。40 S亚基在酿酒酵母细胞中对超过1700个核苷酸进行高持续合成能力的帽依赖性扫描。此外，观察到的表达率表明扫描是由从5'帽复合物释放的未束缚的40 S亚基进行的。出乎意料的是，维持长5' UTR扫描能力的能力更依赖于Ded 1/Dbp 1类型的解旋酶，而不是eIF 4A或eIF 4 B。在酵母无细胞提取物中，扫描显示出降低的持续合成能力，在26 ℃下，估计的净5 '->3'速率约为每秒10个核苷酸。我们已经开发了一个有偏见的双向步行模型的核糖体扫描，提供了一个框架，了解上述意见，以及其他已知的定量和定性特征的这一过程。
The eukaryotic 40S ribosomal subunit locates the translation initiation codon on an mRNA via the so-called scanning process that follows 40S binding to the capped 5' end. This key step in translation is required for the expression of almost all eukaryotic genes, yet the mechanism and dynamics of scanning are unknown. We have performed quantitative studies in vivo and in vitro of the movement of yeast 40S ribosomes along 5' untranslated regions (UTRs) of different lengths. 40S subunits perform cap-dependent scanning with high processivity for more than 1700 nucleotides in cells of Saccharomyces cerevisiae. Moreover, the observed rates of expression indicate that scanning is performed by an untethered 40S subunit that has been released from the 5' cap complex. Unexpectedly, the capability to maintain scanning competence on a long 5' UTR is more dependent on the Ded1/Dbp1 type of helicase than on eIF4A or eIF4B. In a yeast cell-free extract, scanning shows reduced processivity, with an estimated net 5'-->3' rate of approximately 10 nucleotides per second at 26degreesC. We have developed a biased bidirectional walking model of ribosomal scanning that provides a framework for understanding the above observations as well as other known quantitative and qualitative features of this process.