The p53 Pathway Promotes Efficient Mitochondrial DNA Base Excision Repair in Colorectal Cancer Cells

Abstract

The tumor suppressor p53 plays a central role in the DNA damage response. p53 enhances base excision repair (BER), in part, through direct interaction with the repair complex. Mitochondrial DNA (mtDNA) is repaired by a mtBER pathway. Many colorectal cancers harbor mtDNA mutations that are associated with poor prognosis. In addition to modulating the apoptotic response, mitochondria-localized p53 also stimulates mtBER. However, the mechanisms by which p53 enhances colorectal cancer mtBER after stress remain unclear.To explore this, we used colorectal cancer cells isogenic for p53 (HCT116p53+/+ and HCT116p53À/À). p53+/+ cells more efficiently repaired H 2 O 2 damaged DNA in vivo as measured by semiquantitative mtDNA displacement loop PCR. Mitochondrial extracts from p53+/+ cells more efficiently stimulated 32 P-dCTP incorporation into a uracil-oligonucleotide. Recombinant p53 complemented p53À/À mitochondrial extract repair of uracil or 8-oxo-G-containing oligonucleotides. As a measure of DNA glycosylase activity, p53+/+ mitochondrial extracts more efficiently incised uracil or 8-oxo-G oligonucleotides, although recombinant p53 could not stimulate oligonucleotide incision. p53 did not influence mitochondrial apurinic/apyrimidinic endonuclease activity measured by incision of a tetrahydrofuran-oligonucleotide. p53+/+ mitochondrial extracts had higher DNA polymerase-; activity measured by 32 P-dCTP incorporation into a singlenucleotide gap oligonucleotide, and recombinant p53 complemented p53À/À mitochondrial extract DNA polymerase-; activity. mtDNA ligase activity was not affected by p53 status. p53 protein was detected in an inner mitochondrial membrane subfraction containing components of the mtBER complex. Our data suggest that an intact p53 pathway stimulates specific mtBER steps and provides mechanistic insight into the development of mtDNA mutations in colorectal cancer. (Cancer Res 2006; 66(7): 3485-94)

p53 in mitochondria enhances the accuracy of DNA synthesis

“…29 Furthermore, p53 enhances BER through direct interaction with the repair complex in an inner mitochondrial membrane subfraction. 8 The fact that p53 localizes to the mitochondria and interacts with mtDNA and pol g, taken together with our observations that the presence of p53 decreases the amount of incorporation of wrong nucleotide in H1299mit, suggests that p53 may be the fidelity-enhancing component of DNA replication machinery in mitochondria.…”

“…[3][4][5][6] p53 was detected within the inner mitochondrial compartment, where mtDNA and mtBER components localize. 7,8,28 It was of interest to evaluate the incorporation and excision of the wrong nucleotide by mitochondrial extracts derived from isogenic HCT116 cells. p53 was detected in the mitochondrial fraction of HCT116 (p53 þ / þ ) cells (p53 þ / þ )mit), but not of HCT116 (p53À/À) cells (p53À/À)mit) with Do-1 anti-human p53 mAb (Figure 4a).…”

“…6 p53 may be a component of a stress response pathway that involves the upregulation of mitochondrial repair in mouse liver and cancer cells, suggesting the potential role of p53 in maintaining mtDNA stability. 7,8 Mitochondrial DNA, a 16.5-kb circular double-stranded molecule, is replicated by an assembly of enzymes and proteins consisting of DNA polymerase g (pol g), ssDNAbinding protein, DNA helicase and various accessory proteins and transcription factors. 9 Mitochondrial DNA is prone to mutations, as it is localized near the inner mitochondrial membrane in which reactive oxygen species are generated.…”

Mitochondrial DNA alteration in primary and metastatic colorectal cancer: Different frequency and association with selected clinicopathological and molecular markers

“…The link of altered mtDNA, to both TP53 wild-type status and probably downregulated Bcl-2 protein expression in CRC, could point to an intact intrinsic apoptotic pathway, either despite of the types of mtDNA alterations found here or caused by these via a currently unknown mechanism. Preliminary results of basic research demonstrated that mutant mtDNA promotes apoptotic resistance 45,46 and that TP53 enhances base excision repair, 47 thus suggesting a link between wild-type TP53 and intact mtDNA genome. According to our data, the role of mtMSI in the apoptotic pathway could be different from the role of mtDNA mutations.…”

Mitochondrial p53 mediates a transcription-independent regulation of cell respiration and interacts with the mitochondrial F₁F₀-ATP synthase

“…This interaction could account for a higher mtDNA copy number in p53 +/+ vs. p53 −/− cells. [48][49][50][51][52] We and others have previously characterized that endogenous p53 can be located at mitochondria in the absence of exogenous stress, further supporting that p53 has a role in the normal physiology of this organelle. [53][54][55] In the present study, our aim was to better characterize the intramitochondrial localization of p53 and to identify new partners and functions of p53 in mitochondria in the absence of induced stress.…”