title: Modulation of base excision repair of 8-oxoguanine by the nucleotide sequence.
abstract: 8-Oxoguanine (8-oxoG) is a major product of oxidative DNA damage, which induces replication errors and interferes with transcription. By varying the position of single 8-oxoG in a functional gene and manipulating the nucleotide sequence surrounding the lesion, we found that the degree of transcriptional inhibition is independent of the distance from the transcription start or the localization within the transcribed or the non-transcribed DNA strand. However, it is strongly dependent on the sequence context and also proportional to cellular expression of 8-oxoguanine DNA glycosylase (OGG1)-demonstrating that transcriptional arrest does not take place at unrepaired 8-oxoG and proving a causal connection between 8-oxoG excision and the inhibition of transcription. We identified the 5'-CAGGGC[8-oxoG]GACTG-3' motif as having only minimal transcription-inhibitory potential in cells, based on which we predicted that 8-oxoG excision is particularly inefficient in this sequence context. This anticipation was fully confirmed by direct biochemical assays. Furthermore, in DNA containing a bistranded Cp[8-oxoG]/Cp[8-oxoG] clustered lesion, the excision rates differed between the two strands at least by a factor of 9, clearly demonstrating that the excision preference is defined by the DNA strand asymmetry rather than the overall geometry of the double helix or local duplex stability.
authors.affiliation: Institute of Pharmacy and Biochemistry, Johannes Gutenberg University of Mainz, Staudingerweg 5, 55128 Mainz, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Allgayer
authors.forename: Nataliya
authors.initials: N
authors.lastname: Kitsera
authors.forename: Carina
authors.initials: C
authors.lastname: von der Lippen
authors.forename: Bernd
authors.initials: B
authors.lastname: Epe
authors.forename: Andriy
authors.initials: A
authors.lastname: Khobta
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry*; D045647:DNA Glycosylases / Q000378:metabolism; D004260:DNA Repair; D017930:Genes, Reporter; D006147:Guanine / Q000031:analogs & derivatives* / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D009711:Nucleotides / Q000737:chemistry; D014158:Transcription, Genetic
chemical_list: D009711:Nucleotides; C024829:8-hydroxyguanine; D006147:Guanine; D004247:DNA; D045647:DNA Glycosylases; C479058:oxoguanine glycosylase 1, human