p53 in the mitochondria, as a trans-acting protein, provides error-correction activities during the incorporation of non-canonical dUTP into DNA

Abstract

Mutations in mitochondrial DNA is an outcome of errors produced by DNA polymerase γ during replication and failure of the repair mechanism. Misincorporation of non-canonical dUTP leads to mutagenesis or apoptosis, and may contribute to the cytotoxic effects of 5′-fluorouracil chemotherapy. Tumor suppressor p53 protein in the mitochondria displays physical and functional interactions with mitochondrial DNA and polymerase γ, and by its intrinsic 3′→5′ exonuclease activity can diminish the polymerization errors. Here we demonstrate the impact of p53 on incorporation of uracil into DNA examined with mitochondrial fractions, as the source of polymerase γ. p53 in mitochondria facilitates DNA damage repair functions resulting from uracil–DNA misincorporation. Our biochemical studies revealed that the procession of U:A and mismatched U:G lesions enhances in the presence of recombinant or endogenous cytoplasmic p53. p53 in mitochondria can function as an exonuclease/proofreader for polymerase γ by either decreasing the incorporation of non-canonical dUTP into DNA or by promoting the excision of incorporated nucleotide from nascent DNA, thus expanding the spectrum of DNA damage sites exploited for proofreading as a trans-acting protein. The data suggest that p53 may contribute to defense of the cells from consequences of dUTP misincorporation in both normal and tumor cells.

Possible Genetic Risks from Heat-Damaged DNA in Food

“…The experiments included 10 different damaged 2′-deoxynucleosides (structures are shown in Supporting Information, Figure S4) and 4 cell lines (HeLa, MCF-7, HEK293, and SW620). We found that mitochondrial BER activity in cells increased in the presence of several of the damaged 2′-deoxynucleosides tested (Figure b), apparently as a result of defensive responses to increases in lesions in mtDNA . To further investigate the relationship between the enhanced DNA repair activity and salvage pathways that enable the incorporation of damaged nucleoside into DNA, we tested the effect of a chemical inhibitor of a nucleotide sanitization enzyme for one of the damaged components (dU).…”

Mitochondrial DNA replication and repair defects: Clinical phenotypes and therapeutic interventions

“…Towards the last step of the repair process, strand ligation takes place where processed ends of DNA are ligated by LIGIII (DNA ligase III) [166,167]. Numerous other proteins are also implicated in base excision repair including PNKP [145,157,168], PARP1 (poly ADP-ribose polymerase 1) [169][170][171][172], CSB (Cockayne syndrome group B protein) [173,174] and tumour suppressor p53 [175][176][177][178]. However, several investigations have revealed that various alternative DNA repair processes exist in mammalian mitochondria, such as direct reversal (DR), mismatch repair (MMR), and presumably double-strand break repair (DSBR) [3,179].…”

The Role p53 Protein in DNA Repair

“…p53 in cytoplasm can participate through the intermolecular pathway in a dU-damage-associated repair mechanism by its ability to remove preformed 3′-terminal dUs, thus preventing further extension of 3' dU-terminated primer during DNA synthesis by HIV-1 RT. Similarly, p53 in mitochondria can function as an exonuclease/proofreader for pol γ by either decreasing the incorporation of non-canonical dUTP into DNA or by promoting the excision of incorporated dU from nascent DNA, thus expanding the spectrum of DNA damage sites exploited for proofreading as a trans-acting protein [106].…”