KLF5 but not KLF6 transactivates Dβ1 promoter expression. (A) Expression constructs representing full-length KLF5, containing putative activating domain (AD), nuclear localization signal (N), and the zinc-finger (ZF) domain. A dominant-negative KLF5 mutant construct (KLF5DN) lacks the N-terminal 358 amino acids within the activating domain. (B) Effect of vector or KLF5 on reporter gene activity in NIH/3T3 cells. Reporters included the Dβ1 promoter (+6Δ) or a construct containing mutations within the -35, -281, and -314 GC-rich motifs (asterisks). Each was tested in the presence or absence of the Eβ enhancer. (C) Effect of wild-type or KLF5DN expression constructs on Dβ1 promoter constructs without or with the Eβ enhancer. (D) Effect of KLF6 expression on Dβ1 promoter constructs in the absence or presence of Eβ enhancer. Luciferase activity in these assays is expressed relative to the vector-only control cotransfected with the wild-type Dβ1 promoter construct. Average and standard error for 3 independent transfections are presented.