Detection of Topoisomerase Covalent Complexes in Eukaryotic Cells

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• DNA topoisomerases are essential enzymes that manage DNA topology through transient breaks.
• Topoisomerase activity involves a transient covalent intermediate where the enzyme is bound to DNA via a phosphotyrosine linkage.
• Anti-cancer drugs targeting topoisomerases often function by trapping this covalent intermediate, leading to DNA damage and cell death.

Purpose of the Study:

• To develop and describe accurate and sensitive assays for quantifying topoisomerase-DNA complexes.
• To facilitate a better understanding of how drugs targeting topoisomerases function.
• To investigate the role of trapped topoisomerases in maintaining genome stability.

Main Methods:

• Development of two novel quantitative assays: ICE (in vivo complex of enzymes) and RADAR (rapid approach to DNA adduct recovery).
• Isolation of genomic DNA under conditions that preserve covalently bound protein-DNA complexes.
• Quantification of covalently bound proteins using antibodies specific to topoisomerases.

Main Results:

• Successful implementation of ICE and RADAR assays in both mammalian cells and Saccharomyces cerevisiae.
• Demonstration of the assays' ability to accurately measure topoisomerase-DNA covalent complexes.
• Provided examples to enhance the quantitative reliability of these assays.

Conclusions:

• The ICE and RADAR assays provide robust methods for measuring topoisomerase-DNA covalent complexes.
• These assays are valuable tools for studying topoisomerase function, drug mechanisms, and genome stability.
• Further application of these assays can advance research in cancer therapy and DNA repair mechanisms.