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相关概念视频

Improving Translational Accuracy02:07

Improving Translational Accuracy

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Base complementarity between the three base pairs of mRNA codon and the tRNA anticodon is not a failsafe mechanism. Inaccuracies can range from a single mismatch to no correct base pairing at all. The free energy difference between the correct and nearly correct base pairs can be as small as 3 kcal/ mol. With complementarity being the only proofreading step, the estimated error frequency would be one wrong amino acid in every 100 amino acids incorporated. However, error frequencies observed in...
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tRNA Activation02:26

tRNA Activation

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Aminoacyl-tRNA synthetases are present in both eukaryotes and bacteria. Though eukaryotes have 20 different aminoacyl-tRNA synthetases to couple to 20 amino acids, many bacteria do not have genes for all of these aminoacyl-tRNA synthetases. Despite this, they still use all 20 amino acids to synthesize their proteins. For instance, some bacteria do not have the gene encoding the enzyme that couples glutamine with its partner tRNA. In these organisms, one enzyme adds glutamic acid to all of the...
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Transfer RNA Synthesis02:36

Transfer RNA Synthesis

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One of the unique features of tRNA is the presence of modified bases. In some tRNAs, modified bases account for nearly 20% of the total bases in the molecule. Altogether, these unusual bases protect the tRNA from enzymatic degradation by RNases.
Each of these chemical modifications is carried by a specific enzyme, post-transcription. All of these enzymes have unique base and site-specificity. Methylation, the most common chemical modification, is carried by at least nine different enzymes, with...
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Nonsense-mediated mRNA Decay02:27

Nonsense-mediated mRNA Decay

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The Upf proteins that carry out nonsense-mediated decay (NMD) are found in all eukaryotic organisms, including humans. Each protein has an individual role, but they need to work in collaboration. Upf1 is an ATP-dependent RNA helicase that unwinds the RNA helix. Because Upf1 can unwind any RNA, Upf2 and Upf3 are required to help Upf1 discriminate between nonsense and normal mRNAs.
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Mutations

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Overview
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Translation01:31

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Lesson: Translation
Translation is the process of synthesizing proteins from the genetic information carried by messenger RNA (mRNA). Following transcription, it constitutes the final step in the expression of genes. This process is carried out by ribosomes, complexes of protein and specialized RNA molecules. Ribosomes, transfer RNA (tRNA), and other proteins produce a chain of amino acids—the polypeptide—as the end product of translation.
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相关实验视频

Updated: Aug 14, 2025

Removal of an Internal Translational Start Site from mRNA While Retaining Expression of the Full-Length Protein
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短tRNA抗干和突变的eRF1允许停止干的重新分配

Ambar Kachale1,2, Zuzana Pavlíková3, Anna Nenarokova1,2,4

  • 1Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice, Czech Republic.

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|January 11, 2023
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概括

一些原生生物重新分配停止子. 这项研究揭示了一种涉及tRNA修饰和释放因子突变的通用机制,可阻止子重新分配和基因表达调节.

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科学领域:

  • 分子生物学
  • 遗传学
  • 进化生物学

背景情况:

  • 标准的遗传代码在翻译过程中使用特定的代码作为停止信号.
  • 一些有机体,特别是原生体,重新分配了这些停止编码子来编码氨基酸,改变了基本的生物原理.
  • 对于理解基因表达和进化来说,了解阻断子重新分配背后的机制至关重要.

研究的目的:

  • 为了研究之前未描述的trypanosomatid,Blastocrithidia nonstop中停止子重新分配的机制.
  • 确定允许使用停止编码子作为感知编码子的特定遗传和分子适应.
  • 在真核生物中探索这些机制的进化保护和普遍性.

主要方法:

  • 在Blastocrithidia nonstop的7259个蛋白质编码基因中分析框架内停止编码子.
  • 参与停止子重新分配的新型tRNA (tRNAGlu,tRNATrp) 的鉴定和表征.
  • 对不同物种 (B. nonstop,Trypanosoma brucei,Saccharomyces cerevisiae) 的tRNA变异进行工程和表达,以研究它们的功能.
  • 在B中对释放因子1进行突变分析.

主要成果:

  • 在B. nonstop中高度表达的基因中,框架内停止编码子不足;UAA是唯一的终结编码子.
  • UAG和UAA编码子的重新分配涉及新的相关tRNAs.
  • 通过tRNATrpCCA的缩短 (4个基对) 抗干进行了UGA重新分配,使得基合成为可能.
  • 在多个物种中,改造的4-bp tRNATrp变体显示出读数的增加.
  • 一个突变的释放因子1在B. nonstop特别限制了UGA的认可,提高了重新分配.

结论:

  • 布拉斯托克里蒂迪亚不间断使用一种独特的机制,通过tRNA抗干缩短来阻止UGA的子重新分配.
  • 一个修改的释放因子1进一步加强了UGA在B的重新分配.
  • 其他真核生物如Condylostoma magnum也采用了涉及tRNA修饰和释放因子改变的类似策略.
  • 在未相关的真核生物中发现了一种以前未知的,普遍的停止子重新分配机制.