Fig. 2.

The genome editing toolbox. A Repair pathways of DNA double-strand breaks (DSBs) induced by nucleases. B CRISPR-mediated gene interference (CRISPRi) or gene activation (CRISPRa) regulates the activity of CREs by sterically blocking or changing epigenetic modifications. C Base editors used a fused deaminase to catalyze the conversion of C to U (C base editor) or A to I (A base editor) on one strand, followed by DNA repair on the non-edited strand. Eventually, the original C:G (or A:T) is converted to T:A (G:C) during DNA replication. D Primer editing leverages nCas9 to nick the genomic target, after which the reverse transcriptase copies the sequence information from the prime editing guide RNA (pegRNA) and replaces the original sequence at the target site