We found that total p53 level is controlled by the level of mitochondrial Lon in several cancer cell lines (Fig. 5a, b) and the mitochondrial accumulation of p53 is regulated by Lon (Fig. 5e, f), suggesting that the cytoplasmic level (includes mitochondrial fraction) of p53 protein correlates the level of mitochondrial Lon. The gene discussed is TP53; the disease is cancer.