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

Editing window: Positions 4-8

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.

Architecture: Rat APOBEC1 fused to S. aureus Cas9 D10A nickase with UGI, split via Npu intein at Lys534/Cys535

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