title: Nucleotide excision repair- and polymerase eta-mediated error-prone removal of mitomycin C interstrand cross-links.
abstract: Interstrand cross-links (ICLs) make up a unique class of DNA lesions in which both strands of the double helix are covalently joined, precluding strand opening during replication and transcription. The repair of DNA ICLs has become a focus of study since ICLs are recognized as the main cytotoxic lesion inflicted by an array of alkylating compounds used in cancer treatment. As is the case for double-strand breaks, a damage-free homologous copy is essential for the removal of ICLs in an error-free manner. However, recombination-independent mechanisms may exist to remove ICLs in an error-prone fashion. We have developed an in vivo reactivation assay that can be used to examine the removal of site-specific mitomycin C-mediated ICLs in mammalian cells. We found that the removal of the ICL from the reporter substrate could take place in the absence of undamaged homologous sequences in repair-proficient cells, suggesting a cross-link repair mechanism that is independent of homologous recombination. Systematic analysis of nucleotide excision repair mutants demonstrated the involvement of transcription-coupled nucleotide excision repair and a partial requirement for the lesion bypass DNA polymerase eta encoded by the human POLH gene. From these observations, we propose the existence of a recombination-independent and mutagenic repair pathway for the removal of ICLs in mammalian cells.
authors.affiliation: Departments of Experimental Radiation Oncology. Molecular Genetics. Carcinogenesis, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
authors.forename: Huyong
authors.initials: H
authors.lastname: Zheng
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.forename: Amy J
authors.initials: AJ
authors.lastname: Warren
authors.forename: Randy J
authors.initials: RJ
authors.lastname: Legerski
authors.forename: Rodney S
authors.initials: RS
authors.lastname: Nairn
authors.forename: Joshua W
authors.initials: JW
authors.lastname: Hamilton
authors.forename: Lei
authors.initials: L
authors.lastname: Li
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D001483:Base Sequence; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004249:DNA Damage; D004260:DNA Repair; D018076:DNA, Complementary / Q000378:metabolism; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D008156:Luciferases / Q000378:metabolism; D016685:Mitomycin / Q000494:pharmacology*; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009154:Mutation; D009841:Oligonucleotides / Q000494:pharmacology; D010957:Plasmids / Q000378:metabolism; D011995:Recombination, Genetic; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D000099270:Y-Family DNA Polymerases
chemical_list: D000911:Antibodies, Monoclonal; D003432:Cross-Linking Reagents; D018076:DNA, Complementary; D004259:DNA-Directed DNA Polymerase; D008156:Luciferases; D016685:Mitomycin; D009841:Oligonucleotides; C112338:Rad30 protein; D000099270:Y-Family DNA Polymerases