A novel zinc-finger nuclease platform with a sequence-specific cleavage module

Area of Science:

• Molecular Biology
• Gene Editing Technologies
• Enzymology

Background:

• Conventional zinc-finger nucleases (ZFNs) utilize zinc fingers for DNA binding and the FokI endonuclease domain for cleavage.
• Alternative DNA-binding modules like TALE sequences have been explored, but the FokI cleavage domain remains largely unchanged in ZFN designs.

Purpose of the Study:

• To engineer a novel ZFN by replacing the FokI cleavage domain with the restriction endonuclease PvuII.
• To enhance the specificity and fidelity of ZFNs by creating ZF-PvuII fusion constructs.

Main Methods:

• Fusion of a three-zinc-finger array to the PvuII restriction endonuclease.
• Introduction of amino acid substitutions into PvuII to optimize catalytic activity (K(m), k(cat)) and increase DNA cleavage fidelity.
• In vitro and cellular assays to evaluate the cleavage specificity of the engineered ZF-PvuII constructs.

Main Results:

• Engineered ZF-PvuII constructs demonstrated >1000-fold preference for cleavage at addressed DNA sites over unaddressed PvuII sites, both in vitro and in cellulo.
• Unlike ZF-FokI nucleases, the optimized ZF-PvuII system did not induce off-target cleavage even with excess enzyme or prolonged incubation.
• The modified PvuII enzyme exhibited altered kinetic parameters and enhanced fidelity, contributing to the system's specificity.

Conclusions:

• The ZF-PvuII platform represents a viable and highly specific alternative to traditional ZFNs for targeted DNA modification.
• This study introduces a novel strategy for engineering nucleases by combining specific DNA-binding domains with alternative catalytic domains.
• The enhanced specificity of ZF-PvuII has significant implications for the safety and efficacy of gene-editing applications.