XPD localizes in mitochondria and protects the mitochondrial genome from oxidative DNA damage

Abstract

Xeroderma pigmentosum group D (XPD/ERCC2) encodes an ATP-dependent helicase that plays essential roles in both transcription and nucleotide excision repair of nuclear DNA, however, whether or not XPD exerts similar functions in mitochondria remains elusive. In this study, we provide the first evidence that XPD is localized in the inner membrane of mitochondria, and cells under oxidative stress showed an enhanced recruitment of XPD into mitochondrial compartment. Furthermore, mitochondrial reactive oxygen species production and levels of oxidative stress-induced mitochondrial DNA (mtDNA) common deletion were significantly elevated, whereas capacity for oxidative damage repair of mtDNA was markedly reduced in both XPD-suppressed human osteosarcoma (U2OS) cells and XPD-deficient human fibroblasts. Immunoprecipitation-mass spectrometry analysis was used to identify interacting factor(s) with XPD and TUFM, a mitochondrial Tu translation elongation factor was detected to be physically interacted with XPD. Similar to the findings in XPD-deficient cells, mitochondrial common deletion and oxidative damage repair capacity in U2OS cells were found to be significantly altered after TUFM knock-down. Our findings clearly demonstrate that XPD plays crucial role(s) in protecting mitochondrial genome stability by facilitating an efficient repair of oxidative DNA damage in mitochondria.

Mechanistic and biological considerations of oxidatively damaged DNA for helicase-dependent pathways of nucleic acid metabolism

“…Liu et al determined that XPD not only resides in human mitochondria, but also that a deficiency in XPD causes increased mitochondrial reactive oxygen species (ROS) and hypersensitivity to H 2 O 2 as displayed by an accumulation of a prominent mtDNA 4977-bp deletion (referred to as CD) and elevated oxidatively damaged DNA [170]. The recent demonstration that XPD helicase activity is required for NER of nuclear UV-induced DNA damage [171] prompted Liu et al [170] to determine if expression of the XPD ATPase-dead mutant XPD-K48R was incapable of restoring repair of oxidatively damaged mtDNA in XPD-depleted cells. Indeed this was found to be the case, suggesting a universally important role of XPD helicase activity in repair of either bulky nuclear DNA adducts or mitochondrial oxidized base lesions.…”

DNA polymerase β: A missing link of the base excision repair machinery in mammalian mitochondria

“…2E). As expected, the membrane protein VDAC1 was recovered in the pellet fraction, whereas the intermembrane space marker protein SMAC (second mitochondria-derived activator of caspases) was recovered in the supernatant fraction [31,33]. More pol β was recovered in the supernatant fraction as compared to the pellet fraction.…”

“…Although mitochondria import many different proteins from the cytosol, more than 50% of these proteins do not have a classical mitochondrial-targeting sequence, but instead have alternate mechanisms of mitochondrial targeting [71]. Thus, the mechanism of pol β mitochondrial transport is unknown, but this also is true for a number of other mitochondrial DNA enzymes, including Tdp1, MSH5, XPD, MSH5, PARP-1 and pol θ [31,33,53,70,72,73]. …”

“…Initial studies of mtDNA repair focused on UV light-induced DNA damage and suggested mitochondria lack a functional DNA repair mechanism [30]. However, repair mechanisms thought to occur exclusively in the nucleus have been reported in mammalian mitochondria [31–35]. …”

Estudo do papel de mTOR na regulação da atividade de reparo do DNA mitocondrial humano

“…Não há ainda evidências na literatura acerca da existência de reparo por excisão de nucleotídeos na mitocôndria, apesar de componentes dessa via já terem sido identificados em mitocôndrias de mamíferos, como CSA e CSB (Aamann et al, 2010;Kamenisch et al, 2010), e XPD (J. Liu et al, 2015). (Eng et al, 1984;Martel et al, 1977;Vezina et al, 1975).…”