Electron microscopic analysis reveals that replication factor C is sequestered by single-stranded DNA

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• Replication factor C (RF-C) is a crucial eukaryotic protein complex.
• RF-C facilitates DNA replication and repair by loading proliferating cell nuclear antigen (PCNA) onto DNA.
• RF-C's DNA binding is hypothesized to occur at primer/template junctions.

Purpose of the Study:

• To investigate the DNA binding specificity of human RF-C and a specific subunit of Drosophila melanogaster RF-C (dRF-Cp140).
• To determine if RF-C preferentially binds to primer/template junctions or other DNA structures.

Main Methods:

• Electron microscopy was employed to visualize the interaction of RF-C with heteroduplex DNA.
• The binding affinities of both the full human RF-C complex and the DNA-binding domain of dRF-Cp140 were assessed.

Main Results:

• Electron microscopy revealed that both human RF-C and the dRF-Cp140 DNA-binding region bind to single-stranded DNA.
• No specific affinity for the 3' or 5' transition points between single- and double-stranded DNA was observed.
• The data suggest RF-C binding is sequestered by single-stranded DNA rather than primer-template junctions.

Conclusions:

• Human RF-C and the dRF-Cp140 DNA-binding region exhibit affinity for single-stranded DNA.
• The study challenges the prevailing hypothesis of RF-C binding exclusively to primer-template junctions.
• These findings refine our understanding of RF-C's role in DNA replication and repair initiation.