PE2 Prime Editor

Characteristics

First functional prime editing system. Nicks target strand, reverse transcriptase extends 3' flap using pegRNA template, cellular repair resolves intermediate. Lower efficiency than base editors but vastly expanded editing scope. Indel byproducts typically 5-15%.

Architecture: Cas9 H840A nickase fused to engineered reverse transcriptase (M-MLV RT with five mutations). Prime editing guide RNA (pegRNA) contains target-binding sequence plus reverse transcriptase template encoding desired edit.

Capabilities: All 12 base-to-base substitutions, small insertions (tested up to 44 bp), and deletions (tested up to 80 bp) without double-strand breaks or donor DNA. Single programmable system for diverse genomic modifications.

Efficiency features: Basic prime editing without enhancement. Efficiency varies by edit type, genomic context, and cell type. Typically 10-40% editing at optimized sites. Requires only pegRNA design, no separate donor DNA.

References

1. Anzalone et al. (2019). Search-and-replace genome editing without double-strand breaks or donor DNA. Nature - Anzalone 2019 Prime Editing