Table 1 Features of prime editor variants.
From: Emerging trends in prime editing for precision genome editing
Type | Cas protein | Components | Editing frequency | pegRNA type | Features | Study |
|---|---|---|---|---|---|---|
PE1 | Nickase Cas9 (H840A) | RT (M-MLV RT), pegRNA | ~10–20% in HEK293T cells | Linear pegRNA | Initial version of prime editing, demonstrated proof of concept for search-and-replace genome editing | Anzalone et al.14 |
PE2 | Nickase Cas9 (H840A) | Improved RT (M-MLV RT), enhanced pegRNA design | ~20–40% in HEK293T cells | Linear pegRNA | Increased editing efficiency compared with PE1, optimized RT for higher processivity and stability | |
PE3 | Nickase Cas9 (H840A) | RT (M-MLV RT), pegRNA, additional sgRNA for nicking the nonedited strand | ~30–50% in HEK293T cells | Linear pegRNA | Introduced dual nicking to enhance editing efficiency, promotes usage of the edited strand as a template for repair | |
PE4 | Nickase Cas9 (H840A) | RT (M-MLV RT), pegRNA, dominant-negative MLH1 (MLH1dn) to inhibit MMR | ~50–70% in HEK293T cells | Linear pegRNA | Increased editing efficiency by suppressing MMR pathways, reduced indel formation | Chen et al.30 |
PE5 | Nickase Cas9 (H840A) | RT (M-MLV RT), pegRNA, additional sgRNA for nicking the nonedited strand, dominant-negative MLH1 (MLH1dn) | ~60–80% in HEK293T cells | Linear pegRNA | Enhanced efficiency and precision by inhibiting MMR pathways and using additional sgRNA to nick the nonedited strand | |
PE6 | Nickase Cas9 (H840A) | Modified RT (M-MLV RT, PE6d), new compact RT variants (PE6a, PE6b, PE6c), enhanced Cas9 variants (PE6e, PE6f, PE6g), epegRNAs | ~70–90% in HEK293T cells | epegRNA | Variants with compact RT for better delivery, stabilized pegRNAs to reduce degradation | Doman et al.41 |
PE7 | Nickase Cas9 (H840A) | Modified RT (M-MLV RT), epegRNAs, La(1–194) protein fused to prime editor complex | ~80–95% in HEK293T cells | epegRNA with La protein | Improved pegRNA stability and editing efficiency, enhanced editing outcomes in challenging cell types | Yan et al.42 |
Cas12a PE | Nickase Cas12a (R1226A) | RT (M-MLV RT)-MCP, circular RNA for reverse transcription-MS2, crRNA for targeting | Up to 40.75% in HEK293T cells | Circular pegRNA (cpegRNA) | Smaller size compared with Cas9-based systems, preferential targeting of T-rich PAMs, enhanced stability and reduced degradation by circular RNA, potential for multiplex editing | Liang et al.38 |
DPE | Nickase Cas9 (H840A) | MCP-fused DNA-dependent DNA polymerase (phi29), DNA polymerase editing template (DPET) including MS2 loop | Up to 60% in HEK293T cells | Additional DNA template with gRNA | Uses DNA polymerase instead of RT; separate DNA template is easily synthesized and modifiable for cellular stability | Liu et al.45 |
CE | Nickase Cas9 (H840A) | DNA-dependent DNA polymerase, click DNA (clkDNA), HUH endonuclease domain | Up to 25.2% in HCT116 cells | Additional DNA template with gRNA | Ferreira da Silva et al.46 |
