The dCas9-KRAB overexpressing cell line is a powerful genetic tool for transcriptional repression in CRISPR interference (CRISPRi) systems. It employs a nuclease-inactive Cas9 (dCas9) fused with the KRAB domain, a strong transcriptional repressor. Guided by sequence-specific sgRNAs, the dCas9-KRAB complex binds to gene promoters or regulatory regions and recruits chromatin-modifying factors to epigenetically silence gene expression—without introducing DNA breaks or altering the genome. Establishing a stable dCas9-KRAB overexpressing cell line allows precise, reversible, and long-term gene silencing, ideal for loss-of-function studies, functional genomics, epigenetics, and disease modeling, especially when permanent gene knockout is impractical or introduces unwanted effects.