title: DNA lesion-specific co-localization of the Mre11/Rad50/Nbs1 (MRN) complex and replication protein A (RPA) to repair foci.
abstract: The DNA damage response, triggered by DNA replication stress or DNA damage, involves the activation of DNA repair and cell cycle regulatory proteins including the MRN (Mre11, Rad50, and Nbs1) complex and replication protein A (RPA). The induction of replication stress by hydroxyurea (HU) or DNA damage by camptothecin (CAMPT), etoposide (ETOP), or mitomycin C (MMC) led to the formation of nuclear foci containing phosphorylated Nbs1. HU and CAMPT treatment also led to the formation of RPA foci that co-localized with phospho-Nbs1 foci. After ETOP treatment, phospho-Nbs1 and RPA foci were detected but not within the same cell. MMC treatment resulted in phospho-Nbs1 foci formation in the absence of RPA foci. Consistent with the presence or absence of RPA foci, RPA hyperphosphorylation was present following HU, CAMPT, and ETOP treatment but absent following MMC treatment. The lack of co-localization of phospho-Nbs1 and RPA foci may be due to relatively shorter stretches of single-stranded DNA generated following ETOP and MMC treatment. These data suggest that, even though the MRN complex and RPA can interact, their interaction may be limited to responses to specific types of lesions, particularly those that have longer stretches of single-stranded DNA. In addition, the consistent formation of phospho-Nbs1 foci in all of the treatment groups suggests that the MRN complex may play a more universal role in the recognition and response to DNA lesions of all types, whereas the role of RPA may be limited to certain subsets of lesions.
authors.affiliation: Department of Environmental Health, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267, USA.
authors.forename: Jacob G
authors.initials: JG
authors.lastname: Robison
authors.forename: Lu
authors.initials: L
authors.lastname: Lu
authors.forename: Kathleen
authors.initials: K
authors.lastname: Dixon
authors.forename: John J
authors.initials: JJ
authors.lastname: Bissler
mesh_terms: D017766:Acid Anhydride Hydrolases; D015153:Blotting, Western; D002166:Camptothecin / Q000494:pharmacology; D002412:Cations; D018797:Cell Cycle Proteins / Q000096:biosynthesis* / Q000737:chemistry; D002467:Cell Nucleus / Q000378:metabolism; D020552:Comet Assay; D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair; D045643:DNA Repair Enzymes / Q000096:biosynthesis* / Q000737:chemistry; D004277:DNA, Single-Stranded / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000737:chemistry; D005047:Etoposide / Q000737:chemistry / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D006918:Hydroxyurea / Q000494:pharmacology; D000076228:MRE11 Homologue Protein; D046911:Macromolecular Substances / Q000378:metabolism; D008856:Microscopy, Fluorescence; D016685:Mitomycin / Q000494:pharmacology; D008954:Models, Biological; D046912:Multiprotein Complexes / Q000378:metabolism; D009687:Nuclear Proteins / Q000096:biosynthesis* / Q000737:chemistry; D010766:Phosphorylation; D011485:Protein Binding; D051716:Replication Protein A; D013997:Time Factors
chemical_list: D002412:Cations; D018797:Cell Cycle Proteins; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; C121766:MRE11 protein, human; D046911:Macromolecular Substances; D046912:Multiprotein Complexes; C112156:NBN protein, human; D009687:Nuclear Proteins; C497167:RPA1 protein, human; D051716:Replication Protein A; D016685:Mitomycin; D005047:Etoposide; D004247:DNA; D000076228:MRE11 Homologue Protein; D017766:Acid Anhydride Hydrolases; C112158:RAD50 protein, human; D045643:DNA Repair Enzymes; D006918:Hydroxyurea; D002166:Camptothecin