Targeted suppression of the reporter gene by epigenetic suppressors. a. Schematic diagram of suppressor and reporter gene vectors. GAL4: the GAL4 DNA binding domain; GBS: GAL4-binding site; KRAB: kruppel-associated box domain; NSL: nuclear localization signal; pCMV: cytomegalovirus (CMV) promoter; PA: SV40 polyadenylation signal; Sss1: methyltransferase gene from Spiroplasma sp. strain MQ1; vSET: the histone H3 lysine 27 methyltransferase SET domain. Synthetic factors use the GAL4 domain to bind to the GBS site in the target gene vector, where the suppressor domain suppresses the activity of the downstream CMV promoter through epigenetic mechanisms. b. Relative expression of the reporter gene. 293 T cells were transiently co-transfected with 250 ng suppressor vectors, 250 ng luciferase target vector, and 25 ng thymidine kinase promoter-Renilla luciferase reporter (pRL-TK) control vector. The empty pcDNA3.1 vector was used as the study control. Forty-eight hours post-transfection, cells were harvested for luciferase assay. For comparison, the pcDNA3.1 control vector was adjusted to 100%. Each error bar represents the SEM of three independent experiments. a: P <0.05 as compared with the pcDNA3.1 control vector; b: P <0.05 as compared with the Sss1 group.