S. aureus CBE C-terminal Fragment

Compact SaCas9-based cytosine editor split via Npu intein for dual-AAV delivery. Smaller size than SpCas9 enables efficient packaging.

Length: 1000 bp (333 aa)

Type: Cytosine Base Editor

Conversion: C-to-T

Origin: Rat APOBEC1 fused to S. aureus Cas9 D10A nickase, split at Lys534/Cys535

Characteristics

SaCas9 provides ~1 kb size reduction versus SpCas9, enabling more efficient AAV packaging. Recognizes NNGRRT PAM (relaxed compared to NGG). Editing window positions 4-8 from PAM with comparable efficiency to SpCas9-based editors.

Applications

In vivo base editing via dual-AAV delivery where smaller size facilitates packaging and co-transduction. Compatible with engineered AAV serotypes (AAV9, PHP.eB, Anc80) for diverse tissue targeting. Validated for brain, liver, and retina editing in mice.

Limitations

Requires NNGRRT PAM which may limit targeting scope compared to SpCas9 editors. Dual-AAV system requires co-transduction for reconstitution, reducing overall editing efficiency compared to single-vector delivery.

Literature References

  1. Komor et al. (2016). Programmable editing of a target base in genomic DNA without double-stranded DNA cleavage. Nature - Komor 2016 BE3
  2. Levy et al. (2020). Cytosine and adenine base editing of the brain, liver, retina, heart and skeletal muscle of mice via adeno-associated viruses. Nat Biomed Eng - Levy 2020 BE3.9max