FAZF is a transcriptional repressor. (A) 293T cells were cotransfected in quadruplicate with a luciferase reporter gene containing four copies of a high-affinity PLZF binding site (0.15 μg) from the IL-3–receptor promoter linked 5′ to the HSV-tk promoter or the parental tk-luciferase reporter (0.15 μg) along with 0.85 μg of expression vectors for PLZF or FAZF as indicated or the pSG5 expression vector. At 48 hours after transfection, the cells were assayed for luciferase activity. (B) Increasing amounts of the PLZF or FAZF expression vector or a combination of both vectors was cotransfected in quadruplicate along with the IL3-tk-luciferase promoter (0.1 μg). Luciferase activity was assayed as above.