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Single-Molecule Real-Time Visualization of DNA Unwinding by CMG Helicase
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クロモソーム複製中の歪んだDNAをカップリングされたDNAポリメラーゼによって解き放つための溶液
Isabel Kurth1, Roxana E Georgescu, Mike E O'Donnell
1The Rockefeller University, Howard Hughes Medical Institute, 1230 York Avenue, New York, New York 10065, USA.
Nature
|March 29, 2013
まとめ
バクテリアのDNA複製機械 (レプリソーム) は,遅れた鎖ポリメラーゼが頻繁に分離して再結合することを可能にすることで,重要なトポロジカル問題を解決します. 外部要因とは無関係なこのダイナミックなプロセスは,過剰なスーパーコーリングなしにDNA合成が円滑に進むことを保証します.
科学分野:
- 分子生物学は分子生物学である.
- バイオケミストリー バイオケミストリー
- 遺伝学 遺伝学とは
背景:
- DNA複製には,先行性および後退性鎖ポリメラーゼの協調的な作用が必要です.
- カップル複製は,DNAの螺旋状構造のためにトポロジカルな課題を提示し,スーパーコイルの蓄積につながります.
- これらの課題にもかかわらず,ポリメラーゼが結合を維持するメカニズムは十分に理解されていません.
研究 の 目的:
- エシェリキア・コライ・レプリソームのダイナミクスを調べるために.
- DNAポリメラーゼが結合複製中に結合を維持する方法を解明する.
- DNA合成中のトポロジカル問題の解決法を理解する.
主な方法:
- バイオケミカルアッセイをまとめます.
- 単一分子生物物理技術.
- エシェリキヤ大腸におけるレプリソーム動態の分析.
主要な成果:
- 遅滞糸ポリメラーゼは,完成前にオカザキの断片から離散し,一時的な隙間を作り出すことがよくあります.
- この"信号放出"はプライマースとは独立しており,タンパク質トリガーを必要としない.
- 遅滞鎖ポリメラーゼは,レプリソーム内でのプロセシビティが低下し,解離すると復元されます.
結論:
- レプリソームは,後退する鎖ポリメラーゼの一時的な解離を通じて,トポロジカルストレスを管理する.
- 新しく合成されたDNAに蓄積された超螺旋的緊張は,遅滞鎖ポリメラーゼのプロセシビティを減少させる可能性が高い.
- このメカニズムは,トポイソメラーゼに頼らずに,効率的なDNA複製を可能にする.
関連する概念動画
DNA Topoisomerases
Topoisomerases are enzymes that relax overwound DNA molecules during various cell processes, including DNA replication and transcription. These enzymes regulate positive and negative DNA supercoiling without changing the nucleotide sequence. DNA overwinding in a clockwise direction results in positively supercoiled DNA, whereas underwinding in a counterclockwise direction produces negatively supercoiled DNA.
Types and Mechanism of action
Topoisomerases are divided into two main types. Type I...
Types and Mechanism of action
Topoisomerases are divided into two main types. Type I...
Homologous Recombination
The basic reaction of homologous recombination (HR) involves two chromatids that contain DNA sequences sharing a significant stretch of identity. One of these sequences uses a strand from another as a template to synthesize DNA in an enzyme-catalyzed reaction. The final product is a novel amalgamation of the two substrates. To ensure an accurate recombination of sequences, HR is restricted to the S and G2 phases of the cell cycle. At these stages, the DNA has been replicated already and the...
Translesion DNA Polymerases
Translesion (TLS) polymerases rescue stalled DNA polymerases at sites of damaged bases by replacing the replicative polymerase and installing a nucleotide across the damaged site. Doing so, TLS allows additional time for the cell to repair the damage before resuming regular DNA replication.
TLS polymerases are found in all three domains of life - archaea, bacteria, and eukaryotes. Of the different classes of TLS polymerases, members of the Y family are fitted with specialized structures that...
TLS polymerases are found in all three domains of life - archaea, bacteria, and eukaryotes. Of the different classes of TLS polymerases, members of the Y family are fitted with specialized structures that...
The Replisome
DNA replication is carried out by a large complex of proteins that act in a coordinated matter to achieve high-fidelity DNA replication. Together this complex is known as the DNA replication machinery or the replisome.
The synthesis of the leading and lagging strands is a highly coordinated process. To explain this, the “Trombone model” was proposed by Bruce Alberts in 1980. The DNA loop formation starts when a primer is synthesized on the parent lagging strand. The loop grows with the...
The synthesis of the leading and lagging strands is a highly coordinated process. To explain this, the “Trombone model” was proposed by Bruce Alberts in 1980. The DNA loop formation starts when a primer is synthesized on the parent lagging strand. The loop grows with the...
The Replisome
DNA replication is carried out by a large complex of proteins that act in a coordinated matter to achieve high-fidelity DNA replication. Together this complex is known as the DNA replication machinery or the replisome.
The synthesis of the leading and lagging strands is a highly coordinated process. To explain this, the “Trombone model” was proposed by Bruce Alberts in 1980. The DNA loop formation starts when a primer is synthesized on the parent lagging strand. The loop grows with the...
The synthesis of the leading and lagging strands is a highly coordinated process. To explain this, the “Trombone model” was proposed by Bruce Alberts in 1980. The DNA loop formation starts when a primer is synthesized on the parent lagging strand. The loop grows with the...
The DNA Replication Fork
An organism’s genome needs to be duplicated in an efficient and error-free manner for its growth and survival. The replication fork is a Y-shaped active region where two strands of DNA are separated and replicated continuously. The coupling of DNA unzipping and complementary strand synthesis is a characteristic feature of a replication fork. Organisms with small circular DNA, such as E. coli, often have a single origin of replication; therefore, they have only two replication forks, one in...

