Replication fork binding triggers structural changes in the PriA helicase that govern DNA replication restart in E....

Area of Science:

• Molecular Biology
• Genetics
• Structural Biology

Background:

• Bacterial DNA replication requires replisomes, which can prematurely dissociate from replication forks.
• Replication restart pathways are essential for bacterial survival, reloading replisomes to complete chromosome replication.
• The PriA-PriB pathway is the primary mechanism for replication restart in E. coli.

Purpose of the Study:

• To elucidate the structural basis of replication fork specificity for the E. coli PriA-PriB pathway.
• To understand the mechanism by which PriA-PriB selectively targets and re-initiates replication at stalled forks.

Main Methods:

• Cryogenic-electron microscopy (cryo-EM) to determine the structure of a PriA/PriB/replication fork complex.
• Biochemical assays and genetic studies to support structural findings.

Main Results:

• The structure reveals extensive interactions between PriA and the branched DNA of the replication fork.
• PriA undergoes conformational changes, forming a pore around single-stranded lagging-strand DNA and exposing a docking site for PriB.
• This restructuring couples fork recognition to PriA/PriB complex formation.

Conclusions:

• The PriA-PriB pathway utilizes a switch-like mechanism for replication restart initiation.
• PriA's structural adaptability is key to recognizing replication forks and initiating restart.
• This mechanism ensures robust and high-fidelity replication re-initiation, preventing lethal consequences of fork collapse.