Fig. 3

CRISPR-Cas systems for genome editing and other manipulations. A Schematic representation of representative three CRISPR-Cas systems: Cas9, Cas12a, and Cas13a. Their main features and action on the DNA/RNA are depicted. B Paired nickase system: Schematic representation of DBS by a pair of sgRNAs guiding Cas9 nickases. C Prime editor are generated through the fusion of nCas9 with an engineered reverse transcriptase (RT) and employment of a prime-editing guide RNA (pegRNA) that consists of the sgRNA containing a primer binding site (PBS) and the RT template sequence containing the desired edit. D Overview of various applications of dCas9 fusion-based genome manipulations. dCas9 fuses with other effector proteins, including transcriptional repressors (KRAB and SRDX) or activators (VP64 and VPR), epigenetic effectors (LSD1, p300, and ten-eleven translocation [TET1]), and fluorescent proteins (GFP) can be used for transcriptional modulation, epigenetic modification, and genomic imaging. E Mechanisms of single-base editing. a CBE-mediated C-to-T base-editing strategy. Cytidine deaminase is human APOBEC3A. b ABE-mediated A-to-G base-editing strategy. Deaminase is the fusion protein Escherichia coli TadA (transfer RNA adenosine deaminase). c GBE-mediated C-to-A and C-to-G base-editing strategy. The deaminases are activation-induced cytidine deaminase in Escherichia coli and rat APOBEC1 in mammalian cells