Repulsive DNA-DNA interactions accelerate viral DNA packaging in phage Phi29

Area of Science:

• Biophysics
• Molecular Biology
• Virology

Background:

• Motor-driven viral DNA packaging is essential for virus assembly.
• Understanding DNA-DNA interactions is key to elucidating packaging dynamics.

Purpose of the Study:

• To investigate how attractive versus repulsive DNA-DNA interactions influence motor-driven viral packaging dynamics.
• To determine the role of spermidine(3+) in modulating these interactions and packaging efficiency.

Main Methods:

• Utilized optical tweezers to precisely measure forces and dynamics during viral packaging.
• Manipulated DNA-DNA interactions by controlling solution conditions, including the presence of spermidine(3+).

Main Results:

• Repulsive DNA interactions significantly accelerated the viral packaging process.
• Induction of attractive DNA interactions by spermidine(3+) led to heterogeneous dynamics, with some complexes accelerating but most slowing or stalling.
• Attractive interactions appear to induce non-equilibrium DNA conformations that hinder motor function.

Conclusions:

• Repulsive DNA interactions facilitate viral DNA packaging, contrary to theoretical energy optima.
• Attractive interactions, while potentially increasing theoretical spooling energy, impede packaging by creating unfavorable DNA conformations.
• Modulating DNA-DNA interactions offers a potential strategy to control viral packaging efficiency.