Engineering IscB to develop highly efficient minisize editing tools in mammalian cells and embryos

The IscB proteins, as the ancestor of Cas9 endonuclease, hold great promise due to their small size and potential for diverse genome editing. However, their activity in mammalian cells is unsatisfactory. By introducing three residual substitutions in IscB, we observed an increase in activity. Through fusing a sequence-non-specific DNA binding protein domain, the eIscB-D variant achieved higher editing efficiency. Our study suggests that these miniature genome editing tools have great potential for diverse applications.