SP1 plays a pivotal role for basal activity of TIGAR promoter in liver cancer cell lines.

TIGAR expression resulted in down-regulation of glycolysis, reduction of intracellular levels of reactive oxygen species, and protection from apoptosis. Despite biological importance, its promoter has not yet been characterized. In this study, we characterized that transcription factor SP1 plays a pivotal role for basal activity of TIGAR promoter. By 5'RACE, the transcription start site was identified locating at 134 bp upstream of the translation initiation site. Different portions of 5'-flanking and 5'-untranslated regions were fused to a luciferase reporter gene to create reporter plasmids, and constructs were transiently transfected into HepG2, Bel-7402, and Smmc-7721 cell lines for luciferase analysis. A minimal region -56/-4 bearing a SP1-binding site was characterized and plays a vital role. Data from electrophoretic mobility shift assay and chromatin immunoprecipitation showed that SP1 can interact with the SP1-binding site within TIGAR promoter in vitro and in vivo. Conclusively, SPl is indispensable for basal activity of TIGAR promoter.