The ribosome uses two active mechanisms to unwind messenger RNA during translation.
The ribosome uses two active mechanisms to unwind messenger RNA during translation.
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DOI：
10.1038/nature10126
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发表时间：
2011-07-06
期刊：
影响因子：
64.8
通讯作者：
Tinoco I Jr
中科院分区：
文献类型：
--
作者：
Qu X;Wen JD;Lancaster L;Noller HF;Bustamante C;Tinoco I Jr
核糖体将信使RNA编码的遗传信息翻译成蛋白质。mRNA编码区的折叠结构代表了减缓肽延伸率的动力学屏障，因为核糖体必须在其进入位点破坏其在mRNA中遇到的结构，以实现下一个密码子的易位。细胞利用这些结构来创建多种翻译调控策略，如程序化的框架移动、蛋白质表达水平、核糖体定位和共翻译蛋白质折叠。虽然链分离活性是核糖体固有的，不需要外源解旋酶，但其机制尚不清楚。在这里，我们使用单分子光学镊子对mRNA发夹进行分析，发现解码中心相同密码子的翻译速率受到mRNA进入位点折叠结构的G•C含量的极大影响。此外，力施加到发夹的两端，有利于其展开显著加快平移。对其解旋酶活性的力依赖性的定量分析表明，与先前研究的解旋酶不同，核糖体使用两种不同的活性机制来解开mRNA结构：(i)它通过使其热波动偏向开放状态来破坏mRNA进入位点的螺旋结的稳定性，增加核糖体不受阻碍易位的可能性；（ii）在伴随核糖体易位的构象变化过程中，它也会机械地撕裂封闭连接的mRNA单链。我们的研究结果为理解结构mrna调控翻译延伸率的机制奠定了定量的力学基础。
The ribosome translates the genetic information encoded in messenger RNA into protein. Folded structures in the coding region of an mRNA represent a kinetic barrier that slows the peptide elongation rate, as the ribosome must disrupt structures it encounters in the mRNA at its entry site to enable translocation to the next codon. Such structures are exploited by the cell to create diverse strategies for translation regulation, such as programmed frameshifting, protein expression levels, ribosome localization, and cotranslational protein folding. Although strand separation activity is inherent to the ribosome, requiring no exogenous helicases, its mechanism is still unknown. Here, using a single-molecule optical tweezers assay on mRNA hairpins, we find that the translation rate of identical codons at the decoding center is greatly influenced by the G•C content of folded structures at the mRNA entry site. Furthermore, force applied to the ends of the hairpin to favor its unfolding significantly speeds translation. Quantitative analysis of the force dependence of its helicase activity reveals that the ribosome, unlike previously studied helicases, uses two distinct active mechanisms to unwind mRNA structure: (i) it destabilizes the helical junction at the mRNA entry site by biasing its thermal fluctuations toward the open state, increasing the probability for the ribosome to translocate unhindered; and (ii) it also mechanically pulls apart the mRNA single-strands of the closed junction during the conformational changes that accompany ribosome translocation. Our results establish a quantitative mechanical basis for understanding the mechanism of regulation of the elongation rate of translation by structured mRNAs.
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DOI：
10.1073/pnas.0905046106
发表时间：
2009-08-04
影响因子：
11.1
作者：
Chen, Gang;Chang, Kung-Yao;Tinoco, Ignacio, Jr.
通讯作者：
Tinoco, Ignacio, Jr.
影响因子：
2
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DOI：
10.1073/pnas.0709793104
发表时间：
2007-12-11
影响因子：
11.1
作者：
Lionnet, Timothee;Spiering, Michelle M.;Croquette, Vincent
通讯作者：
Croquette, Vincent
影响因子：
5.6
作者：
Kim S;Schroeder CM;Xie XS
通讯作者：
Xie XS