Effects of DNA lesions on the transcription reaction of mitochondrial RNA polymerase: implications for bypass RNA synthesis on oxidative DNA lesions.
Oxidative DNA lesions inhibit the transcription of RNA polymerase II, but in the presence of transcription elongation factors, the transcription can bypass the lesions. Single-subunit mitochondrial RNA polymerase (mtRNAP) catalyses the synthesis of essential transcripts in mitochondria where reactive oxidative species (ROS) are generated as by-products. The occurrence of RNA synthesis by mtRNAP at oxidative DNA lesions remains unknown. Purified mtRNAP and a complex of RNA primer/DNA template containing a single DNA lesion, such as ROS-induced 8-oxoguanine (8-oxoG), two isomeric thymine glycols (5R-Tg or 5S-Tg), the UV-induced cis-syn cyclobutane pyrimidine dimer (CPD) and the pyrimidine(6-4)pyrimidone photoproduct (6-4pp), or a spontaneous common DNA lesion, a base-loss-induced apurinic/apyrimidinic (AP) site, were used for in vitro RNA synthesis assays. In this report, we show that mtRNAP bypassed the oxidative DNA lesions of non-bulky 8-oxoG and 5R-Tg and 5S-Tg with pausing sites but did not bypass the UV-induced DNA lesions and the AP site. The bacteriophage T7 phage RNA polymerase, which is homologous to mtRNAP, bypassed 8-oxoG but stalled at 5R-Tg and 5S-Tg. As expected, although translesion RNA synthesis in 8-oxoG on the DNA templates generated incorrect transcripts with a G:C to T:A transversion, the synthesis in Tg could lead to the correct transcripts with no transcriptional mutagenesis. Collectively, these data suggest that mtRNAP may tolerate the mitochondrial genome containing oxidative DNA lesions induced by ROS from the side effects of an ATP generation reaction.
Graduate School of Engineering Science, Osaka University Graduate School of Engineering Science, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan.
Nozomi
N
Nakanishi
Atsushi
A
Fukuoh
Dongchon
D
Kang
Shigenori
S
Iwai
Isao
I
Kuraoka
D004249:DNA Damage / Q000528:radiation effects; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry / Q000378:metabolism; D006147:Guanine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction; D011740:Pyrimidine Dimers / Q000737:chemistry / Q000378:metabolism; D011744:Pyrimidinones / Q000737:chemistry / Q000378:metabolism; D012313:RNA / Q000096:biosynthesis* / Q000737:chemistry; D012319:RNA Polymerase II / Q000235:genetics / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000737:chemistry / Q000378:metabolism; D014158:Transcription, Genetic; D014466:Ultraviolet Rays; D014764:Viral Proteins / Q000737:chemistry / Q000378:metabolism
D011740:Pyrimidine Dimers; D011744:Pyrimidinones; D017382:Reactive Oxygen Species; D014764:Viral Proteins; C024829:8-hydroxyguanine; D006147:Guanine; D012313:RNA; D012319:RNA Polymerase II; C062210:bacteriophage T7 RNA polymerase; D012321:DNA-Directed RNA Polymerases