Novel DNA mismatch-repair activity involving YB-1 in human mitochondria

Abstract

Maintenance of the mitochondrial genome (mtDNA) is essential for proper cellular function. The accumulation of damage and mutations in the mtDNA leads to diseases, cancer, and aging. Mammalian mitochondria have proficient base excision repair, but the existence of other DNA repair pathways is still unclear. Deficiencies in DNA mismatch repair (MMR), which corrects base mismatches and small loops, are associated with DNA microsatellite instability, accumulation of mutations, and cancer. MMR proteins have been identified in yeast and coral mitochondria; however, MMR proteins and function have not yet been detected in human mitochondria. Here we show that human mitochondria have a robust mismatch-repair activity, which is distinct from nuclear MMR. Key nuclear MMR factors were not detected in mitochondria, and similar mismatch-binding activity was observed in mitochondrial extracts from cells lacking MSH2, suggesting distinctive pathways for nuclear and mitochondrial MMR. We identified the repair factor YB-1 as a key candidate for a mitochondrial mismatch-binding protein. This protein localizes to mitochondria in human cells, and contributes significantly to the mismatch-binding and mismatch-repair activity detected in HeLa mitochondrial extracts, which are significantly decreased when the intracellular levels of YB-1 are diminished. Moreover, YB-1 depletion in cells increases mitochondrial DNA mutagenesis. Our results show that human mitochondria contain a functional MMR repair pathway in which YB-1 participates, likely in the mismatch binding and recognition steps.

Role of tyrosyl-DNA phosphodiesterase (TDP1) in mitochondria

“…TDP1 is also a plausible candidate for removing 3′-phosphoglycolate (see Fig. 3C) and 3′-deoxyribose adducts, which can be produced by ROS either directly by attack of the deoxyribose backbone (24,48,55,57) or indirectly after the processing of oxidized bases by DNA glycosylases with AP lyase activity (15,16,57). For instance, 8-oxoguanine-DNA glycosylase (OGG1) has an associated lyase activity that breaks the phosphodiester backbone 3′ to the abasic site with generation of 5′-phosphate and 3′-blocking groups (15).…”

“…However, mismatch repair (16) and DNA double-strand break (DSB) end joining (17)(18)(19) activities have been reported in mitochondria. Recently, several reports have focused on the existence of long-patch BER (LP-BER) by the flap endonucleases FEN-1 and DNA2 in mitochondria (13,(20)(21)(22)(23).…”

The anti‐tumour compound, RH1, causes mitochondria‐mediated apoptosis by activating c‐Jun N‐terminal kinase

“…Additionally, we examined whether RH1 induces synthesis of JNK protein in mitochondria. As chloramphenicol has been reported to inhibit mitochondrial protein synthesis (Kroon, 1965;de Souza-Pinto et al, 2009), cells were treated with RH1 in the presence or absence of chloramphenicol, and Western blotting using an anti-JNK antibody was subsequently performed. As shown in Figure 7C, pretreatment with chloramphenicol in the presence of RH1 did not change the level of expression of JNK protein for 24 h in whole cell lysates.…”

Nothing in Excess—Lessons Learned from the Expression of High-Mobility Group Proteins Type a in Non-Cancer and Cancer Cells

“…therefore, mechanisms for repair of other types of lesions could be deemed redundant and therefore lost in the evolutionary process. it seems that the only exception is the special case of mismatch repair, a particular type of neR endowed with strand specificity, as the DNA polymerases which carry out the final step in any type of DNA repair have an inherent error rate and may incorporate mismatched nucleotides, which, unrepaired, may cause base substitution during the next cycle of replication (39). Recombination is also not an option for repair of mitochondrial DnA.…”