FIGURE 4.

Requirement of the minimal promoter of the Tfr2 gene for transactivation by HNF4α. A, sequence alignment of the proximal promoter of the Tfr2 gene in mouse, human, rat, rabbit, gorilla, chimpanzee, cow, dolphin, horse, panda, and elephant. Predicted HNF4α-binding site is boxed. Completely conserved nucleotides among the species are shown by asterisks. B, mutations were introduced into the HNF4α-binding sites in the proximal promoter of the Tfr2 gene. Empty vector or HNF4α expression vector was co-transfected with the mutated proximal promoter and the minimal distal promoter, and the enhancer activity was measured. C, mutations were introduced into the HNF4α-binding sites and GC-rich sequences in the Tfr2 promoter. Empty vector or HNF4α expression vector was co-transfected with the mutated promoter, and the enhancer activity was measured. The normalized activity ± S.D. (n = 3) is presented as promoter activity based on empty vector-transfected control.