hSIR2(SIRT1) functions as an NAD-dependent p53 deacetylase

DNA damage-induced acetylation of p53 protein leads to its activation and e ither growth arrest or apoptosis. We show here that the protein product of the gene hSIR2(SIRT1), the human homolog of the S. cerevisiae Sir2 protein known to be involved in cell aging and in the response to DNA damage, binds and deacetylates the p53 protein with a specificity for its C-terminal Lys 382 residue, modification of which has been implicated in the activation of p53 as a transcription factor. Expression of wild-type hSir2 in human cell s reduces the transcriptional activity of p53. In contrast, expression of a catalytically inactive hSir2 protein potentiates p53-dependent apoptosis a nd radiosensitivity. We propose that hSir2 is involved in the regulation of p53 function via deacetylation.