Targeted activation of gene expression dCas9-Suntag A gene activation system that consists of a dCas9 fused to a repeated GCN4 peptide tag array and an anti-GCN4 peptide single-chain variable fragment (scFv) antibody fused to a transcriptional activator, such as VP64. By recruiting multiple copies of the transcriptional activator to the target gene transcription starting site using a guide RNA, the SunTag system achieves robust transcriptional activation, exceeding the activation levels of dCas9-VP64 alone.