Structure and Function of the PriC DNA Replication Restart Protein.

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• DNA replication complexes (replisomes) can dissociate from chromosomes due to collisions with barriers.
• Replisome dissociation necessitates reloading to prevent incomplete replication and cell death.
• Bacteria utilize DNA replication restart pathways involving fork remodeling and helicase reloading.

Purpose of the Study:

• To elucidate the structural basis of the bacterial PriC protein's function in DNA replication restart.
• To understand the mechanism by which PriC facilitates the reloading of the replicative helicase.
• To define the role of PriC in recruiting helicase loaders to stalled replication forks.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy to determine the structure of full-length PriC.
• Site-directed mutagenesis to investigate the function of specific PriC residues.
• Biochemical assays to assess DnaB helicase loading and protein-protein interactions.

Main Results:

• The NMR structure reveals PriC as a compact α-helical bundle with adjacent ssDNA and SSB binding sites.
• Disruption of key interaction sites on PriC impairs DnaB helicase loading onto SSB-bound DNA.
• PriC directly interacts with DnaB and the DnaB·DnaC complex, acting as a scaffold.

Conclusions:

• PriC functions as a scaffold protein, recruiting the DnaB·DnaC helicase loader complex to stalled replication forks.
• The structural insights explain how PriC bridges interactions between SSB/ssDNA and the helicase machinery.
• This mechanism is crucial for efficient DNA replication restart in bacteria.