iScienceDec 16, 2025

Base editing of both DNA strands at separate sites using a small CRISPR protein Cas12f1

CRISPR Gene Editing Weekly Brief ↗PubMed ↗DOI ↗

Updated Jun 27, 2026

Abstract

Essence

Small Cas12f1-based base editors enabled cytosine or adenine editing on both DNA strands within distinct target windows in a plasmid system.

Evidence

The evidence is a CRISPR base-editor engineering experiment using dCas12f1-deaminase fusion proteins tested on target plasmid sequences in Escherichia coli.

Caveat

The work is limited to engineered constructs and plasmid targets in E. coli, so performance in mammalian genomes or therapeutic contexts remains untested here.

Simplified

CRISPR-associated base editors have been established as genome editing tools that enable base conversions in targeted DNA sequences, without generating double-strand breaks. Here, we describe the development of new base editors based on CRISPR-Cas12f1, a miniature Cas protein of only 422 amino acids. Chimeric constructs have been generated by fusing a catalytically inactive dCas12f1, to either a cytosine deaminase or an adenine deaminase. Using these synthetic fusion proteins, systematic analyses have been performed on base editing of a target sequence on a plasmid in. Interestingly, apart from the previously described base editing of the displaced non-target DNA strand, we also observed efficient editing of the target DNA strand. This effect was not observed for Un1Cas12f1 BEs. In addition to the small size of AsCas12f1 base editors, its unique editing profile makes it a valuable addition to the CRISPR-Cas toolbox. Escherichia coli