TY - JOUR

T1 - The mitochondrial transcription factor A functions in mitochondrial base excision repair

AU - Canugovi, Chandrika

AU - Maynard, Scott

AU - Bayne, Anne-Cécile V

AU - Sykora, Peter

AU - Tian, Jingyan

AU - de Souza-Pinto, Nadja C

AU - Croteau, Deborah L

AU - Bohr, Vilhelm A

N1 - Published by Elsevier B.V.

PY - 2010/10/5

Y1 - 2010/10/5

N2 - 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 ¿ (pol ¿). 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 aOGG1 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.

AB - 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 ¿ (pol ¿). 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 aOGG1 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.

KW - DNA Damage

KW - DNA Glycosylases

KW - DNA Repair

KW - DNA, Mitochondrial

KW - DNA-Binding Proteins

KW - DNA-Directed DNA Polymerase

KW - Guanine

KW - Hela Cells

KW - Humans

KW - Mitochondrial Proteins

KW - Oxidative Stress

KW - Reactive Oxygen Species

KW - Transcription Factors

KW - Tumor Suppressor Protein p53

KW - Uracil-DNA Glycosidase

U2 - 10.1016/j.dnarep.2010.07.009

DO - 10.1016/j.dnarep.2010.07.009

M3 - Journal article

C2 - 20739229

VL - 9

SP - 1080

EP - 1089

JO - DNA Repair

JF - DNA Repair

SN - 1568-7864

IS - 10

ER -