Fig. 1: PARP1 is present in purified mitochondria.

a Purified mitochondria from wild-type (WT) and PARP1-knockout (KO) HeLa cells and whole-cell lysates (WCL) were prepared. Mitochondrial quality was assessed by probing western blots with the indicated antibodies. b Purified cytosolic fractions, mitochondrial fractions, and WCLs from WT HeLa cells were prepared. Mitochondrial preparations were treated with proteinase K without or with Triton X-100 on ice for 30 min to strip the mitochondrial outer membrane or mitochondrial matrix proteins, respectively. c Mitochondria were purified from WT or PARP1-KO HeLa cells, and suborganellar mitochondrial compartments were isolated. Intact mitochondria (Mito), outer membrane (OM), inner membrane (IM), and matrix fractions were isolated and analyzed by western blotting with the indicated antibodies. d Input mitochondrial DNA quality evaluation. Mitochondria were purified from WT and PARP1-KO cells, and 1% of the mitochondrial DNA for the PARP1-ChIP reaction mixture was subjected to real-time PCR using the indicated mitochondrial or nuclear DNA-specific primers (n = 4). e Mitochondria were purified from WT or KO HeLa cells, and PARP1-ChIP was performed using an antibody that detects the N-terminal half of PARP1 (n = 7). Separate two-sample t tests were conducted, and then a false discovery rate (FDR) approach was used to adjust the p values for multiple testing. f PARP1-ChIP was performed using an antibody that binds to the PARP1 DNA-binding domain. ChIP-purified mitochondrial DNA was subjected to qPCR analysis of the indicated mitochondrial genomic loci (n = 7). Error bars represent the standard deviation. *, <0.05; **, <0.01; ***, <0.001.