Analyzing the dynamics of DNA replication in Mammalian cells using DNA combing

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Chromosome duplication is vital for cell identity and genome stability.
• DNA replication initiates from numerous origins, but only a subset is activated per cell.
• Cell-to-cell variability in origin firing complicates population-based replication studies.

Purpose of the Study:

• To describe a method for analyzing chromosome replication dynamics at the single-cell level.
• To enable quantitative measurements of DNA synthesis features in mammalian cells.

Main Methods:

• Utilizing DNA combing, a biophysical technique for DNA fiber stretching.
• Visualizing ongoing DNA synthesis in single DNA molecules from pulse-labeled cells.
• Purifying and analyzing Mb-sized DNA molecules to measure replication parameters.

Main Results:

• DNA combing allows visualization of DNA synthesis along single DNA molecules.
• Quantitative data on fork velocity, fork asymmetry, and inter-origin distances can be obtained.
• Global instant fork density can be measured in asynchronous mammalian cell cultures.

Conclusions:

• DNA combing provides a powerful tool for studying chromosome replication dynamics in single cells.
• This method overcomes limitations of population-based techniques for analyzing replication heterogeneity.
• The described protocol facilitates detailed insights into mammalian DNA replication processes.