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. 2020 Mar 15;10(10):4374–4382. doi: 10.7150/thno.43360

Figure 1.

Figure 1

Examples of CRISPR/Cas9 technological advances. (a) Cas9 is directed by single guide RNA (sgRNA) to the target sequence. Double stranded DNA breaks are subsequently repaired by cellular DNA repair machinery via the NHEJ or HDR pathway. (b) dCas9 fused with transcriptional activators or repressors activates or inhibits the expression of a target gene. These systems are called CRISPRa or CRISPRi. dCas9 indicates catalytically inactive dead Cas9, which is able to bind the target DNA without cutting. CRISPRa, CRISPR activators to activate transcriptional process; CRISPRi, CRISPR inhibitors to interference transcriptional process. (c) Base editors are the combination of Cas9 D10A nickase with cytidine or adenine deaminase to induce G->T or A->G transition. Prime editor, different from base editors, is the fusion protein of Cas9 H840A nickase and reverse transcriptase. It can achieve up to 12 types of base-to-base conversions, and targeted insertions and deletions without DSBs or donor DNA templates. pegRNA, prime editing guide RNA.