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. 2020 Jun 30;8:711. doi: 10.3389/fbioe.2020.00711

FIGURE 4.

FIGURE 4

Orthogonal CRISPR systems. (A) The orthogonal tri-functional CRISPR system that combines transcriptional activation, transcriptional interference, and gene deletion (CRISPR-AID). This orthogonal tri-functional CRISPR system employed dLbCpf1-VP for CRISPRa, dSpCas9-RD1152 for CRISPRi, and SaCas9 for CRISPRd (gene deletion), which recognized different type of sgRNA and PAMs. dLbCpf1, dCpf1 from Lachnospiraceae bacterium ND2006; dSpCas9, dCas9 from S. pyogenes; SaCas9, Cas9 from S. aureus. (B) The orthogonal CRISPR system with different RNA scaffolds. The gRNA fused with MS2 is used for activation through binding of MCP-VP64 or MCP-SoxSR93A. The gRNA fused with com is used for repression through binding of Com-KRAB. Alternatively, a sgRNA without MS2 or com scaffold can hinder gene expression either. (C) CRISPR and CRISPRi via different crRNA length. Cas12a triggers DSB and genome editing with 20 bp-spacer in crRNA, while it blocks transcription with a short crRNA (16 bp-spacer).