SIRT7 and cancer: Interestingly, SIRT3, the main deacetylase in mitochondria, regulated p21Cip1 expression at the translational level, whereas SIRT7, which is predominantly nuclear, regulated the transcription of p21Cip1 through histone deacetylation at H3K18, thereby avoiding the increase in p21Cip1 levels in cancer cells.