Fig. 6.

SIRT7-mediated deacetylation of NPM stimulates p53 transcriptional activity. (A) p53-dependent luciferase activity in U2OS cells transfected with p53, WT, and K2R NPM (n = 6). (B) Luciferase assay for p53 activity in scrambled and SIRT7 KD stable U2OS cells 5 h after exposure to 10 J/m² UVC (n = 6). (C) qRT-PCR analysis of mRNA expression of p53 target genes (P21Waf1, EI24, and DDB2) in control (scrambled) and SIRT7 KD U2OS cells 5 h after UVC irradiation (10 J/m²). β-Actin was used as a loading control. Quantification of average mRNA levels relative to β-actin ± SD is shown in the histograms (n = 6). (D) EdU (5-ethynyl-2′-deoxyuridine) staining of scrambled and SIRT7 KD cells either left untreated or following exposure to UVC irradiation (10 J/m², 5 h). Cell nuclei were counterstained with DAPI. (Scale bars, 20 μm.) The percentage of EdU-positive cells is shown in the histograms. A minimum of 100 cells was analyzed for each experiment (n = 3). (E) Scheme depicting the putative mechanisms of NPM regulation by SIRT7 following UV-induced genotoxic stress. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.