Human promyelocytic HL-60 cells can be differentiated into macrophage-like cells by treatment with 12-O-tetra decanoylphorbol-13-acetate (TPA). Certain 5' upstream regions of the zinc finger protein (ZNF)-encoding genes contain duplicated GGAA motifs, which are frequently found in the TPA-responding gene promoter regions. To examine transcriptional responses to TPA, 5'flanking regions of human zinc finger CCCH-type containing, antiviral, ZNF252, ZNF343, ZNF555, ZNF782 and zinc finger nfx-1-type containing 1 (ZNFX1) genes were isolated by polymerase chain reaction (PCR) and ligated into a multiple-cloning site of the pGL4.10[luc2] vector. Transient transfection and a luciferase assay revealed that the ZNFX1 promoter most prominently responded to the TPA treatment. Deletion and point mutation experiments indicated that the duplicated GGAA motif in the 100-bp region positively responded to TPA. In addition, reverse transcription-quantitative PCR and western blotting showed that the mRNA and protein of ZNFX1 accumulate during the differentiation of HL-60 cells. These results indicated that expression of the TPA-inducible ZNFX1 gene, which belongs to the group of interferon-responsive genes, is regulated by the cis-action of the duplicated GGAA motif.