TP53-regulated inhibitor of apoptosis 1, also known as TRIAP1, contains a p53-binding site within its second exon and the reduction of expression by small interfering RNA enhanced apoptosis, whereas overexpression protected cells from apoptosis caused by DNA damage. TRIAP1 is induced significantly when cells have a low level of genotoxic stresses, but not when DNA damage is severe. TRIAP1 can modulate apoptotic pathways through interaction with Hsp70 that probably inhibits activity of apoptosis protease activating factor-1. Recombinant human TRIAP1, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.