Direct visualisation of post-replication gap formation at the bacterial RRS.

Area of Science:

• Genomics
• Molecular Biology
• DNA Replication

Background:

• Replication risk sequences (RRS) are novel genomic elements influencing DNA replication.
• RRS in E. coli are conserved G-quadruplex-containing repeats crucial for genome stability.
• Their precise role in triggering replication gaps remains incompletely understood.

Purpose of the Study:

• To directly visualize the in vitro function of RRS during DNA replication.
• To investigate the mechanism by which RRS induce post-replication gaps.
• To assess the impact of RRS orientation on gap formation frequency.

Main Methods:

• Single-molecule visualization techniques.
• In vitro DNA replication assays.
• ssGAP-seq for detecting single-stranded DNA (ssDNA).

Main Results:

• RRS on the lagging-strand template efficiently trigger gap formation upon replisome encounter.
• RRS on the leading-strand template also induce gaps, albeit less frequently.
• Rolling-circle assays confirm lagging-strand gap formation, indicating complementary strand activity.

Conclusions:

• RRS are potent triggers of DNA gap formation during replication.
• The orientation of RRS influences their efficiency in gap induction.
• Findings suggest a potential role for eukaryotic G-quadruplexes in similar DNA repair processes.