Genome-wide specificity of dCpf1 cytidine base editors

Nat Commun. 2020 Aug 13;11(1):4072. doi: 10.1038/s41467-020-17889-9.

Abstract

Cpf1-linked base editors broaden the targeting scope of programmable cytidine deaminases by recognizing thymidine-rich protospacer-adjacent motifs (PAM) without inducing DNA double-strand breaks (DSBs). Here we present an unbiased in vitro method for identifying genome-wide off-target sites of Cpf1 base editors via whole genome sequencing. First, we treat human genomic DNA with dLbCpf1-BE ribonucleoprotein (RNP) complexes, which convert C-to-U at on-target and off-target sites and, then, with a mixture of E. coli uracil DNA glycosylase (UDG) and DNA glycosylase-lyase Endonuclease VIII, which removes uracil and produces single-strand breaks (SSBs) in vitro. Whole-genome sequencing of the resulting digested genome (Digenome-seq) reveals that, on average, dLbCpf1-BE induces 12 SSBs in vitro per crRNA in the human genome. Off-target sites with an editing frequency as low as 0.1% are successfully identified by this modified Digenome-seq method, demonstrating its high sensitivity. dLbCpf1-BEs and LbCpf1 nucleases often recognize different off-target sites, calling for independent analysis of each tool.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Clustered Regularly Interspaced Short Palindromic Repeats / genetics
  • Cytidine / genetics
  • Cytidine / metabolism*
  • DNA / genetics
  • DNA / metabolism
  • Endonucleases / genetics
  • Endonucleases / metabolism*
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Gene Editing
  • Genome, Human / genetics
  • HEK293 Cells
  • High-Throughput Nucleotide Sequencing / methods
  • Humans
  • RNA, Guide, CRISPR-Cas Systems
  • Whole Genome Sequencing / methods*

Substances

  • Cytidine
  • DNA
  • Endonucleases