PML is a potent tumor suppressor and proapoptotic factor and is functionally 
regulated by post-translational modifications such as phosphorylation, 
sumoylation, and ubiquitination. Histone deacetylase (HDAC) inhibitors are a 
promising class of targeted anticancer agents and induce apoptosis in cancer 
cells by largely unknown mechanisms. We report here a novel post-transcriptional 
modification, acetylation, of PML. PML exists as an acetylated protein in HeLa 
cells, and its acetylation is enhanced by coexpression of p300 or treatment with 
a HDAC inhibitor, trichostatin A. Increased PML acetylation is associated with 
increased sumoylation of PML in vitro and in vivo. PML is involved in 
trichostatin A-induced apoptosis and PML with an acetylation-defective mutation 
shows an inability to mediate apoptosis, suggesting the importance of PML 
acetylation. Our work provides new insights into PML regulation by 
post-translational modification and new information about the therapeutic 
mechanism of HDAC inhibitors.