Using a mammalian one-hybrid system, we compared the transcriptional activities of 61 KRAB-ZNFs, or approximately one-seventh of the total genes in the family, which were selected from subfamilies that included various types of KRAB domains. HEK293 BQ-788 sodium salt were transfected by GAL4 DNA-binding domain-fused KRAB-ZNF (GAL4DBD-KRABZNF) expression clones with pGL4.31-SV40 reporter plasmid. pBIND vector which expresses GAL4DBD was used as a control instead of GAL4DBD-KRABZNF clones. The transfection efficiency was normalized by an internal control, Renillaluciferase activity expressed by pBIND-based vectors. Relative firefly luciferase activity was expressed as the ratio of luciferase activities driven by GAL4DBD-KRABZNFs to those driven by GAL4DBD. As shown in Fig. 1A, most of the KRAB-ZNFs exhibit transcription repression activity, with the exception of ZNF436, ZNF3, ZNF286A, and ZNF496, though this activity differs in strength from protein to protein under the relative luciferase activity of 0.5. It has been reported that ZNF496 functions as a transcriptional activator and inhibits transcriptional repression of Jumonji/Jarid2 by physical interaction [14], which is consistent with our results.