Genome-wide analysis of replication timing by next-generation sequencing with E/L Repli-seq

Area of Science:

• Genomics
• Molecular Biology
• Cell Biology

Background:

• Cellular DNA replication occurs during S phase following a programmed sequence known as replication timing (RT).
• Differences in replication timing correlate with mutation rates, gene activity, chromatin states, and nuclear positioning.
• Replication timing is dynamic during development and is frequently altered in various diseases.

Purpose of the Study:

• To present E/L Repli-seq, a novel protocol for analyzing genome-wide replication timing.
• To provide a rapid, robust, and cost-effective method for assessing replication timing using next-generation sequencing.
• To enable the study of links between cellular processes and replication timing.

Main Methods:

• Cells are pulse-labeled with BrdU, and distinct early and late S-phase fractions are isolated using flow cytometry.
• Nascent DNA from each fraction is immunoprecipitated, followed by next-generation sequencing.
• Data processing generates a bedGraph file quantifying the ratio of nascent DNA in early versus late S-phase fractions.

Main Results:

• E/L Repli-seq provides genome-wide sequence data comparable to existing methods like Repli-chip.
• The protocol offers an increased dynamic range and detailed sequence information.
• Computational pipelines are provided for allelic asynchrony analysis and comparison with Repli-chip data.

Conclusions:

• E/L Repli-seq is a valuable extension for analyzing replication timing with enhanced genomic resolution.
• The protocol is accessible, requiring basic laboratory skills and computational understanding.
• This method facilitates a deeper understanding of replication timing's role in biological processes and disease.