Phage-assisted Evolution Research Articles

Combining a Base Deaminase Mutator with Phage-Assisted Evolution.

Phage-assisted evolution has emerged as a powerful technique for improving a protein's function by using mutagenesis and selective pressure. However, mutations typically occur throughout the host's genome and are not limited to the gene-of-interest (GOI): these undesirable genomic mutations can yield host cells that circumvent the system's selective pressure. Our system targets mutations specifically toward the GOI by combining T7 targeted mutagenesis and phage-assisted evolution. This system improves the structure and function of proteins by accumulating favorable mutations that can change its binding affinity, specificity, and activity.

Expanding the genome-targeting scope of a compact Cas9 using phage-assisted evolution.

Expanding the genome-targeting scope of a compact Cas9 using phage-assisted evolution.

Phage-assisted evolution and protein engineering yield compact, efficient prime editors

Prime editing enables a wide variety of precise genome edits in living cells. Here we use protein evolution and engineering to generate prime editors with reduced size and improved efficiency. Using phage-assisted evolution, we improved editing efficiencies of compact reverse transcriptases by up to 22-fold and generated prime editors that are 516-810 base pairs smaller than the current-generation editor PEmax. We discovered that different reverse transcriptases specialize in different types of edits and used this insight to generate reverse transcriptases that outperform PEmax and PEmaxΔRNaseH, the truncated editor used in dual-AAV delivery systems. Finally, we generated Cas9 domains that improve prime editing. These resulting editors (PE6a-g) enhance therapeutically relevant editing in patient-derived fibroblasts and primary human T-cells. PE6 variants also enable longer insertions to be installed invivo following dual-AAV delivery, achieving 40% loxP insertion in the cortex of the murine brain, a 24-fold improvement compared to previous state-of-the-art prime editors.

Genetic code expansion: Synthetases pick up the PACE.

Phage-assisted evolution can rapidly improve the efficiency and substrate specificity of orthogonal aminoacyl-tRNA synthetases. Furthermore, the crystal structure of the pyrrolysyl-tRNA synthetase N-terminal domain reveals the basis for these improvements and provides a structural rationale for orthogonality.