Target-AID Cytosine Base Editor

Alternative cytosine base editor using sea lamprey cytidine deaminase. Narrower editing window (positions 2-4) with reduced cellular toxicity.

Length: 1000 bp(333 aa)

Type: Adenine Base Editor

Conversion: A-to-G (via C-to-T intermediate)

Editing window: Positions 2-4 (narrower)

Origin: Sea lamprey PmCDA1 cytidine deaminase

Architecture

PmCDA1 cytidine deaminase from sea lamprey fused to Cas9 D10A nickase. Deaminates cytosine on single-stranded DNA, indirectly creating A-to-G edits on opposite strand.

Characteristics

Narrow editing window at positions 2-4 upstream of PAM (18 bases from PAM). Lower efficiency than APOBEC1-based editors but useful when PAM placement is suboptimal. Functions through base excision repair pathway rather than direct replication.

Applications

Alternative C-to-T editing when ABE7.10 or BE3/BE4 PAM placement prevents targeting. Validated in yeast, mammalian cells, and plant systems with reduced toxicity. Effective for applications tolerating lower efficiency in exchange for reduced cellular stress.

Limitations

Lower editing efficiency compared to BE3/BE4 family at most targets. Editing window position further from PAM limits target site selection. Indirect mechanism via base excision repair increases variability in editing outcomes.

Literature References

  1. Nishida et al. (2016). Targeted nucleotide editing using hybrid prokaryotic and vertebrate adaptive immune systems. Science - Nishida 2016 Target-AID