p53 and Mitochondrial DNA

Abstract

The roles and actions of the tumor suppressor protein p53 have been extensively studied with regard to nuclear events, including transcription and DNA damage repair. However, the direct roles of p53 in mitochondrial DNA (mtDNA) replication and function are less well understood. Studies herein used a mitochondrial-targeted p53 (MTS-p53) to determine its effects on both mtDNA abundance and mitochondrial function. MTS-p53 decreased cellular proliferation and mtDNA abundance in HepG2 cells transfected with wild-type (WT) human p53. When MTS-p53 cells were treated with the nucleoside reverse transcriptase inhibitor (NRTI), 2',3'-dideoxycytidine or 2',3'-dideoxyinosine, mtDNA depletion that resembled untransfected controls was observed in both instances. p53-Overexpressing cells showed reduced mitochondrial function by oximetry, including a reduction in maximal respiratory capacity and reserve capacity. A truncated p53 (MTS-p53-290) was generated for localization exclusively to the mitochondria. MTS-p53-290 cells proliferated at control levels but displayed decreased mtDNA abundance and mitochondrial function with NRTI treatment. The MTS-p53-290 cells demonstrated that only the nuclear fraction of p53 controlled cellular proliferation, which was supported by the MTS-p53 results. Data herein indicate that overexpression of p53 in the mitochondria reduces mtDNA abundance and increases the sensitivity of mammalian cells to NRTI exposure by reducing mitochondrial function.

Mitochondrial matrix P53 sensitizes cells to oxidative stress

“…This study exploited a novel p53 construct that overexpresses p53 that is targeted within the mitochondrial matrix (Koczor et al, 2012). This was accomplished because the construct capitalized on the addition of a mitochondrial targeting sequence on the N-terminal side of human p53 while simultaneously removing the region encoding amino acids 291–393 to eliminate intrinsic nuclear localization of native p53 polypeptide (Fig.…”

“…Mitochondrial matrix-targeted p53 was designed as previously described (Koczor et al, 2012). Briefly, site-directed mutagenesis (Stratagene/Agilent, Santa Clara, CA) was utilized to introduce BsiWI restriction sites around the nuclear localization sequence contained in the C-terminal portion of WT p53 (amino acids 291–393) of a commercially available WT p53 plasmid (Clontech, Mountain View, CA).…”

“…We previously characterized a novel p53 construct that over-expresses p53 exclusively within the mitochondrial matrix (Koczor et al, 2012). This construct contains: 1) the mitochondrial targeting sequence from ornithine transcarbamylase attached to the N-terminus of WT-p53, and 2) truncation of the nuclear localization sequence (amino acids 291–393) in the C-terminus of WT-p53.…”

“…This construct contains: 1) the mitochondrial targeting sequence from ornithine transcarbamylase attached to the N-terminus of WT-p53, and 2) truncation of the nuclear localization sequence (amino acids 291–393) in the C-terminus of WT-p53. This construct, termed p53–290, demonstrated that mitochondrial matrix p53 sensitizes cells to antiretroviral compounds ddC (2′,3′-dideoxycytidine) and ddI (2′,3′-dideoxyinosine) (Koczor et al, 2012). Due to the increased risk of oxidative stress-induced mtDNA damage as a result of leakage from the electron transport chain, we next explored the impact of mitochondrial p53 in presence of chemically-induced oxidative stress with H 2 O 2 exposure (McKenzie et al, 2004).…”

Transcriptional Regulation of the Human Genes that Encode DNA Repair- and Mitochondrial Function-Associated Proteins

“…One recent study revealed that mitochondrial disulfide relay causes translocation of p53 into mitochondria to facilitate its function for repairing oxidative damage to mitochondrial DNA [29]. However, overexpression of p53 in mitochondria would lead to depleted mitochondrial DNA abundance and a reduction in oxidative stress [30]. Oncogenic RAS-induced mitochondrial dysfunction, which causes oncogene induced senescence, is dependent on either p53 or RB [31].…”