Characterization of the human zinc finger nfx­1­type containing 1 encoding ZNFX1 gene and its response to 12­O­tetradecanoyl­13­acetate in HL­60 cells.

Human promyelocytic HL­60 cells can be differentiated into macrophage­like cells by treatment with 12­O­tetra decanoylphorbol­13­acetate (TPA). Certain 5' upstream regions of the zinc finger protein (ZNF)­encoding genes contain duplicated GGAA motifs, which are frequently found in the TPA­responding gene promoter regions. To examine transcriptional responses to TPA, 5'flanking regions of human zinc finger CCCH­type containing, antiviral, ZNF252, ZNF343, ZNF555, ZNF782 and zinc finger nfx­1­type containing 1 (ZNFX1) genes were isolated by polymerase chain reaction (PCR) and ligated into a multiple­cloning 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 100­bp region positively responded to TPA. In addition, reverse transcription­quantitative PCR and western blotting showed that the mRNA and protein of ZNFX1 accumulate during the differentiation of HL­60 cells. These results indicated that expression of the TPA­inducible ZNFX1 gene, which belongs to the group of interferon­responsive genes, is regulated by the cis­action of the duplicated GGAA motif.