A cell-penetrating peptide suppresses the hypoxia inducible factor-1 function by binding to the helix-loop-helix domain of the aryl hydrocarbon receptor nuclear translocator

► Ainp1 is an ARNT-interacting peptide. ► Functional TAT fusion of Ainp1 can be obtained from inclusion bodies by limited dialysis. ► TAT fusion of Ainp1 penetrates into HeLa, MCF-7, and Hep3B cells. ► TAT fusion of Ainp1 suppresses the HRE-driven luciferase gene expression. ► TAT fusion of Ainp1 suppresses the cobalt-chloride-dependent HIF-1 target gene activation.