Structural mechanisms of PriA-mediated DNA replication restart.

Area of Science:

• Molecular Biology
• Structural Biology
• DNA Replication

Background:

• DNA replication machinery (replisomes) can dissociate upon encountering DNA damage or obstacles, halting replication.
• Replication restart pathways are crucial for cell survival, involving recognition of stalled forks and replisome re-initiation.
• In bacteria, the PriA DNA helicase orchestrates replication restart by recognizing specific DNA structures and interacting with ssDNA-binding proteins (SSBs).

Purpose of the Study:

• To elucidate the structural mechanisms by which PriA binds replication fork DNA and interacts with SSBs.
• To understand how PriA coordinates replication restart reactions following replisome dissociation.

Main Methods:

• Determined crystal structures of full-length bacterial PriA.
• Determined crystal structures of PriA in complex with SSB.
• Analyzed the structural arrangement and interactions within PriA and PriA-SSB complexes.

Main Results:

• Revealed a modular structure of PriA with DNA-binding domains surrounding its helicase core, poised for branched DNA binding.
• Demonstrated PriA's capacity for simultaneous binding to replication fork DNA structures and SSB.
• Showed that PriA modulates SSB/DNA complexes, exposing potential replication initiation sites.

Conclusions:

• The modular structure of PriA facilitates recognition of diverse replication fork structures.
• PriA's interaction with SSB is key to exposing replication initiation sites for restart.
• A model is proposed for how PriA links replication fork recognition to the initiation of replication restart.