Targeting Holliday junctions by origin DNA-binding protein of herpes simplex virus type 1

Area of Science:

• Molecular Biology
• Virology
• Structural Biology

Background:

• Herpes simplex virus type 1 (HSV1) origin binding protein (OBP) is crucial for viral DNA replication.
• Understanding OBP's DNA binding properties is essential for elucidating viral replication mechanisms.

Purpose of the Study:

• To investigate the interaction of HSV1 OBP with synthetic DNA structures, specifically Holliday junctions (HJs).
• To compare OBP's binding affinity to HJs versus duplex and single-stranded DNA.
• To characterize the complexes formed between OBP and HJs and OBP's enzymatic activity on HJs.

Main Methods:

• Electrophoresis mobility shift assay (EMSA)
• Förster resonance energy transfer (FRET) method
• Biochemical assays for DNA processing

Main Results:

• OBP shows a strong preference for binding to three-way and four-way DNA junctions over duplex or single-stranded DNA.
• OBP forms distinct complexes with HJs, including tetrameric and octameric forms, and a stacked arm complex in the presence of Mg²⁺.
• OBP catalyzes the processing of HJs with specific 3'-terminal tails in the presence of ATP and Mg²⁺.

Conclusions:

• OBP's preference for HJs suggests it induces significant DNA structural changes at the viral origin of DNA replication (OriS).
• These structural changes likely involve DNA bending, partial melting, and the formation of junction structures at specific binding sites.
• OBP's ability to bind and process DNA junctions highlights its multifaceted role in HSV1 DNA replication initiation.