Frequent exchange of the DNA polymerase during bacterial chromosome replication

Area of Science:

• Molecular Biology
• Microbiology
• Genetics

Background:

• The bacterial replisome is a complex machine responsible for DNA replication.
• Previous in vitro studies suggested high replisome stability contributes to processivity in *Escherichia coli*.

Purpose of the Study:

• To investigate the dynamic behavior of the *E. coli* replisome in vivo during DNA replication.
• To understand the molecular basis of replisome processivity and flexibility.

Main Methods:

• Utilized live-cell fluorescence microscopy to observe replisome dynamics in *E. coli*.
• Examined the association and exchange of key replisome subassemblies, such as Pol III* and DnaB helicase.

Main Results:

• The Pol III* subassembly dynamically disengages and exchanges with free copies during DNA synthesis.
• The DnaB helicase remains stably associated with the replication fork.
• These findings challenge the established semi-discontinuous model of DNA replication.

Conclusions:

• The *E. coli* replisome exhibits dynamic instability in its subassemblies, particularly Pol III*, which contributes to processivity and fork flexibility.
• A fully discontinuous DNA replication mechanism is proposed, where both leading and lagging strand synthesis are frequently interrupted.