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Published on: August 19, 2014
Chromosomol DNA fragments from mouse cells exposed to an intercalating agent contain a 175-kdalton terminal
Abstract:
A 175 kdalton (kDa) polypeptide is bound covalently to the chromosomal DNA fragments from mouse cells exposed to the intercalating agent 4'-[(9-acridinyl)-amino]methansulphon-m-anisidide. Electron microscopy shows a terminal protein on the DNA fragments, whose 5'-termini are blocked. Since the relative molecular mass of topoisomerase II polypeptide chains is also about 175 kDa and topoisomerase II inhibitors prevent intercalator-induced DNA fragmentation, we propose that the polypeptide bound covalently to the 5'-terminus of the DNA fragments is a polypeptide derived from frequently integrated topoisomerase II operating to normalize torsional stress resulting from intercalation.
Insights
A protein is covalently attached to mouse DNA fragments after exposure to an intercalating agent. This protein is likely topoisomerase II, which helps manage DNA stress caused by the agent.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Intercalating agents can induce DNA fragmentation in cells.
- Topoisomerase II is a crucial enzyme involved in managing DNA topology and preventing DNA breakage.
- The precise mechanism linking intercalator-induced DNA fragmentation to specific enzymes remains under investigation.
Purpose of the Study:
- To identify the protein covalently bound to chromosomal DNA fragments in mouse cells treated with 4'-[(9-acridinyl)-amino]methansulphon-m-anisidide.
- To elucidate the role of this protein in the DNA fragmentation process induced by intercalating agents.
Main Methods:
- Treatment of mouse cells with the intercalating agent 4'-[(9-acridinyl)-amino]methansulphon-m-anisidide.
- Isolation and analysis of chromosomal DNA fragments.
- Electron microscopy to visualize protein-DNA interactions.
- Comparison of the molecular mass of the bound polypeptide with known enzymes.
Main Results:
- A 175 kilodalton (kDa) polypeptide was found covalently bound to chromosomal DNA fragments.
- Electron microscopy revealed this protein to be a terminal protein, with DNA fragments exhibiting blocked 5'-termini.
- The molecular mass of the bound polypeptide matches that of topoisomerase II.
Conclusions:
- The polypeptide covalently bound to the 5'-termini of DNA fragments is proposed to be derived from topoisomerase II.
- Topoisomerase II likely integrates into DNA to normalize torsional stress induced by the intercalating agent.
- This interaction explains the observed DNA fragmentation and suggests a protective role for topoisomerase II under intercalator stress.
