title: The mitochondrial transcription factor A functions in mitochondrial base excision repair.
abstract: Mitochondrial transcription factor A (TFAM) is an essential component of mitochondrial nucleoids. TFAM plays an important role in mitochondrial transcription and replication. TFAM has been previously reported to inhibit nucleotide excision repair (NER) in vitro but NER has not yet been detected in mitochondria, whereas base excision repair (BER) has been comprehensively characterized in these organelles. The BER proteins are associated with the inner membrane in mitochondria and thus with the mitochondrial nucleoid, where TFAM is also situated. However, a function for TFAM in BER has not yet been investigated. This study examines the role of TFAM in BER. In vitro studies with purified recombinant TFAM indicate that it preferentially binds to DNA containing 8-oxoguanines, but not to abasic sites, uracils, or a gap in the sequence. TFAM inhibited the in vitro incision activity of 8-oxoguanine DNA glycosylase (OGG1), uracil-DNA glycosylase (UDG), apurinic endonuclease 1 (APE1), and nucleotide incorporation by DNA polymerase γ (pol γ). On the other hand, a DNA binding-defective TFAM mutant, L58A, showed less inhibition of BER in vitro. Characterization of TFAM knockdown (KD) cells revealed that these lysates had higher 8oxoG incision activity without changes in αOGG1 protein levels, TFAM KD cells had mild resistance to menadione and increased damage accumulation in the mtDNA when compared to the control cells. In addition, we found that the tumor suppressor p53, which has been shown to interact with and alter the DNA binding activity of TFAM, alleviates TFAM-induced inhibition of BER proteins. Together, the results suggest that TFAM modulates BER in mitochondria by virtue of its DNA binding activity and protein interactions.
authors.affiliation: Laboratory of Molecular Gerontology, NIA, National Institutes of Health, Baltimore, MD 21224, United States.
authors.forename: Chandrika
authors.initials: C
authors.lastname: Canugovi
authors.forename: Scott
authors.initials: S
authors.lastname: Maynard
authors.forename: Anne-Cécile V
authors.initials: AC
authors.lastname: Bayne
authors.forename: Peter
authors.initials: P
authors.lastname: Sykora
authors.forename: Jingyan
authors.initials: J
authors.lastname: Tian
authors.forename: Nadja C
authors.initials: NC
authors.lastname: de Souza-Pinto
authors.forename: Deborah L
authors.initials: DL
authors.lastname: Croteau
authors.forename: Vilhelm A
authors.initials: VA
authors.lastname: Bohr
mesh_terms: D004249:DNA Damage; D045647:DNA Glycosylases / Q000378:metabolism; D000074002:DNA Polymerase gamma; D004260:DNA Repair; D004272:DNA, Mitochondrial / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000378:metabolism; D006147:Guanine / Q000031:analogs & derivatives / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D024101:Mitochondrial Proteins / Q000235:genetics* / Q000378:metabolism*; D018384:Oxidative Stress / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D051981:Uracil-DNA Glycosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D004272:DNA, Mitochondrial; D004268:DNA-Binding Proteins; D024101:Mitochondrial Proteins; D017382:Reactive Oxygen Species; C499631:TFAM protein, human; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; C422562:mitochondrial transcription factor A; C024829:8-hydroxyguanine; D006147:Guanine; D000074002:DNA Polymerase gamma; D004259:DNA-Directed DNA Polymerase; D045647:DNA Glycosylases; D051981:Uracil-DNA Glycosidase; C479058:oxoguanine glycosylase 1, human