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スパイナッチのクロロプラストの転写システムにおけるクロロプラスト転送RNAの生物合成
Cell
|December 1, 1983
まとめ
研究者は,スパナッチとEuglena gracilisのトランスファーRNA (tRNA) 遺伝子発現を研究するために,クロロプラストのインビトロ転写システムを開発しました. このシステムは,特定のtRNA遺伝子を成功裏に転写し,処理し,重要な規制DNA配列を明らかにしました.
科学分野:
- 分子生物学は分子生物学である.
- 植物科学 植物科学について
- 遺伝学 遺伝学とは
背景:
- クロロプラストには,核とは異なる独自の遺伝物質と転写機構があります.
- クロロプラストの遺伝子発現,特にtRNA合成の理解は,臓器細胞の機能を理解するために極めて重要です.
- 以前の研究では,クロロプラストのゲノムにtRNA遺伝子を特定しましたが,詳細な分析には体外転写システムが必要です.
研究 の 目的:
- 機能的なクロロプラストの in vitro 転写システムを開発し,特徴づけること.
- スピーナッツとEuglena gracilisのクロロプラストからの特定のtRNA遺伝子の転写と処理を調査する.
- クロロプラストのtRNA遺伝子転写の開始と処理に関与する規制DNA配列を特定する.
主な方法:
- スパイナッチとEuglena gracilisのエキスを用いたクロロプラストのインビトロ転写システムの開発.
- 改変されたDNAテンプレートを使用して特定のtRNA遺伝子 (trn) の転写.
- トランスクリプトの識別と処理確認のためのRNA指紋分析.
- ほうれん草のtrnM2ロクスの側面配列におけるデレーション変異体の構築と分析.
主要な成果:
- インビトロシステムは,スパナッチ (trnM2,trnV1,trnl1) とエウグレナ・グラシリス (trnV1-trnN1-trnR1-trnL1クラスタ) のtRNA遺伝子を成功裏に転写した.
- tRNAMetm,tRNAlle1,tRNALeuを含む正しく処理されたトランスクリプトが特定されました.
- クロロプラスト3'ヌクレオチジルトランスファーゼの活性が成熟したtRNAにCCA添加のために確認されました.
- スパナキのtrnM2ロカス上流の -56から -85の間のDNA配列は,最大限の転写に不可欠であるが,処理には欠かせない.
結論:
- 確立されたクロロプラストのインビトロ転写システムは,tRNA遺伝子発現の研究に有効です.
- 特定の上流DNA配列は,クロロプラストのtRNA遺伝子転写の開始を調節する上で重要な役割を果たします.
- クロロプラストRNAポリメラーゼは,tRNAの転写に関与しており,rRNAの転写を担当するポリメラーゼとは異なる.
関連する概念動画
Transfer 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...
Riboswitches
Riboswitches are non-coding mRNA domains that regulate the transcription and translation of downstream genes without the help of proteins. Riboswitches bind directly to a metabolite and can form unique stem-loop or hairpin structures in response to the amount of the metabolite present. They have two distinct regions – a metabolite-binding aptamer and an expression platform.
The aptamer has high specificity for a particular metabolite which allows riboswitches to specifically regulate...
The aptamer has high specificity for a particular metabolite which allows riboswitches to specifically regulate...
Protein Transport to the Stroma
Chloroplasts are triple membrane structures with an outer membrane, an inner membrane, and a thylakoid membrane, each containing distinct metabolite transporters, membrane translocons, and enzymes. Appropriate sorting and translocating these proteins to their correct membrane systems is essential for chloroplast function.
Protein complexes called the translocon of the outer chloroplast membrane or TOC complex, and the translocon of the inner chloroplast membrane or TIC complex mediate the...
Protein complexes called the translocon of the outer chloroplast membrane or TOC complex, and the translocon of the inner chloroplast membrane or TIC complex mediate the...
Protein Transport to the Outer Chloroplast Membrane
Chloroplast outer membrane proteins encoded by the nucleus are synthesized in the cytosol. Soon after synthesis, they bind cytosolic factors such as 14-3-3 protein and the Hsp70 chaperones that keep these precursors in an unfolded state until their translocation.
Two models describe the mechanism of precursor recognition and entry across the outer membrane through the TOC complex. Model 1 suggests the newly synthesized precursor binds to the TOC receptor 159 and forms a complex.
Two models describe the mechanism of precursor recognition and entry across the outer membrane through the TOC complex. Model 1 suggests the newly synthesized precursor binds to the TOC receptor 159 and forms a complex.
Transfer 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...
Protein Transport to the Inner Chloroplast Membrane
Proteins targeted to the inner chloroplast membrane, or plastid proteins, are transported by two general pathways: the stop-transfer and the re-insertion or post-import pathways. Most plastid proteins carry N-terminal transit sequences and internal import sequences targeting it to the specific chloroplast subcompartment. Proteins targeted by the stop-transfer pathway have internal hydrophobic sequences that inhibit their translocation into the stroma. As a result, these precursors are arrested...

