Improving cytidine and adenine base editors by expression optimization and ancestral reconstruction

Nat Biotechnol. 2018 Oct;36(9):843-846. doi: 10.1038/nbt.4172. Epub 2018 May 29.


Base editors enable targeted single-nucleotide conversions in genomic DNA. Here we show that expression levels are a bottleneck in base-editing efficiency. We optimize cytidine (BE4) and adenine (ABE7.10) base editors by modification of nuclear localization signals (NLS) and codon usage, and ancestral reconstruction of the deaminase component. The resulting BE4max, AncBE4max, and ABEmax editors correct pathogenic SNPs with substantially increased efficiency in a variety of mammalian cell types.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenine / metabolism*
  • CRISPR-Cas Systems
  • Codon
  • Cytidine / genetics*
  • DNA / genetics*
  • Gene Editing
  • HEK293 Cells
  • Humans


  • Codon
  • Cytidine
  • DNA
  • Adenine