The transduction of His-TAT-p53 fusion protein into the human osteogenic sarcoma cell line (Saos-2) and its influence on cell cycle arrest and apoptosis. The p53 gene is a tumor suppressor gene. It encodes a nuclear phosphoprotein p53 involved in the regulation of cell cycle arrest and apoptosis to maintain the genomic integrity of the cell. As mutations of p53 gene are found in most human cancers, p53 protein becomes a hot target in the research of anticancer therapy. In the present study, an 11-amino acid domain of TAT protein which has been demonstrated to be able to transduce across cell membranes was fused with p53. The result revealed that the fusion protein His-TAT-p53 accumulated in the nucleus and inhibited the growth of the Saos-2 cells. Besides apoptosis, an increased percentage of G2 phase suggested that the transduction of His-TAT-p53 into cells might be associated with a G2 arrest of cell cycle.