核から輸出する前にtRNAの校正とアミノアシル化を行う
1Department of Biomolecular Chemistry, University of Wisconsin-Madison, 1300 University Avenue, Madison, WI 53-706, USA.
Science (New York, N.Y.)
|December 16, 1998
まとめ
成熟型移転RNA (tRNA) は,核から細胞プラズマに輸出される. tRNAの核アミノアシレーションは,品質管理の役割を果たし,機能的な分子のみが輸出されることを保証します.
科学分野:
- 分子生物学は分子生物学である.
- 細胞生物学 細胞生物学
- 遺伝学 遺伝学とは
背景:
- 転送RNA (tRNA) は,タンパク質合成に不可欠な分子である.
- tRNAのバイオゲネシスと成熟は,核で起こります.
- 細胞核から細胞プラズマへの成熟したtRNAの輸出は,細胞の重要なプロセスです.
研究 の 目的:
- 成熟したトランスファーRNA (tRNA) の核輸出のメカニズムを調査する.
- tRNAの輸出と品質管理における核アミノアシレーションの役割を決定する.
主な方法:
- 実験は,Xenopusの卵細胞を用いて行われました.
- tRNAの合成,処理,および輸出の分析.
- 輸出への影響を評価するために,tRNAアミノアシレーションの抑制.
主要な成果:
- 成熟したtRNAは,Ran.GTPに依存した方法で細胞質に輸出されます.
- 核品質管理メカニズムは,欠陥または未成熟のtRNAの輸出を防止します.
- tRNAの核アミノアシレーションが観察され,潜在的な機能的校正メカニズムであることが示されました.
- 特定のtRNAのアミノアシレーションを阻害することで,その細胞質の出現を遅らせ,効率的なエクスポートの重要性を示した.
結論:
- 核アミノアシレーションは,新たに合成されたtRNAsの品質管理における重要なステップとして機能します.
- この機能的校正は,成熟した機能的なtRNAのみがタンパク質合成のために細胞質に輸出されることを保証します.
関連する概念動画
02:01pre-mRNA Processing
In eukaryotic cells, transcripts made by RNA polymerase are modified and processed before exiting the nucleus. Unprocessed RNA is called precursor mRNA or pre-mRNA to distinguish it from mature mRNA.
Once about 20-40 ribonucleotides have been joined together by RNA polymerase, a group of enzymes adds a “cap” to the 5’ end of the growing transcript. In this process, a 5’ phosphate is replaced by modified guanosine that has a methyl group attached to it (7-Methyl guanosine). This 5’ cap helps the...
Once about 20-40 ribonucleotides have been joined together by RNA polymerase, a group of enzymes adds a “cap” to the 5’ end of the growing transcript. In this process, a 5’ phosphate is replaced by modified guanosine that has a methyl group attached to it (7-Methyl guanosine). This 5’ cap helps the...
02:36Transfer RNA Synthesis
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...
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...
02:26tRNA Activation
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...
02:07Improving Translational Accuracy
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...
02:36Transfer RNA Synthesis
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...
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...
02:26tRNA Activation
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...