图5. CRISPR干扰系统的工作原理
(A) dCas9阻止RNA聚合酶(RNAP)结合基因启动子, sgRNA介导dCas9结合目的基因启动子, 使RNAP (红色)无法与该基因启动子结合并进行转录; (B) dCas9阻断RNAP的转录延伸, sgRNA介导dCas9结合目的基因开放阅读框(ORF), 使RNAP无法继续转录延伸; (C) 转录抑制子阻止RNAP结合基因启动子, dCas9与转录抑制子(灰色)融合, 抑制子会阻止RNAP与目的基因启动子的结合; (D) 阻遏结合域(RBD)阻止目的基因的转录激活, dCas9与RBD (棕色)融合, RBD阻断转录因子(TFs)与目的基因的结合, 并与TFs结合形成强阻遏物抑制基因的转录表达。PAM: 原间隔序列邻近基序

Figure 5. Technical principles of CRISPR interference system
(A) dCas9 prevents RNA polymerase (RNAP) from binding to gene promoter, sgRNA mediated dCas9 binding to the target gene promoter, so that RNAP (red) can not bind to the gene promoter to start transcribing; (B) dCas9 blocks the transcriptional extension of RNAP, sgRNA mediates dCas9 binding to the target gene open reading frame (ORF), making RNAP unable to continue transcriptional extension; (C) Transcriptional repressors prevent RNAP from binding to gene promoters, dCas9 fuses with the transcription inhibitor (gray), which prevents the binding of RNAP to the promoter of the target gene; (D) The repressor binding domain (RBD) blocks the transcriptional activation of the target gene, dCas9 fuses with the RBD (brown), RBD blocked the binding of transcription factors (TFs) to the target gene and combined with TFs to form a strong repressor to inhibit the transcription of the gene. PAM: Protospacer adjacent motif