dCas9::GS is an artificial transcriptional activator that contains a nuclease-dead form of the Streptococcus pyogenes Cas9 gene (contains mutations in both nuclease domains), a truncated ligand-binding domain from the Homo sapiens progesterone receptor (PGR, HGNC:8910) and the transcriptional activation domain from the Homo sapiens RELA gene (HGNC:9955). This driver can be used to overexpress a target gene of interest from its endogenous genomic locus, by combining it with a single guide RNA (sgRNA) that targets sequences upstream of the gene of interest's transcription start site. The presence of the PGR ligand-binding domain means that transcriptional activation can only occur in the presence of the anti-progestin mifepristone (RU486) (FBrf0240569).