title: Mystery of DNA repair: the role of the MRN complex and ATM kinase in DNA damage repair.
abstract: Genomes are subject to a number of exogenous or endogenous DNA-damaging agents that cause DNA double-strand breaks (DSBs). These critical DNA lesions can result in cell death or a wide variety of genetic alterations, including deletions, translocations, loss of heterozygosity, chromosome loss, or chromosome fusions, which enhance genome instability and can trigger carcinogenesis. The cells have developed an efficient mechanism to cope with DNA damages by evolving the DNA repair machinery. There are 2 major DSB repair mechanisms: nonhomologous end joining (NHEJ) and homologous recombination (HR). One element of the repair machinery is the MRN complex, consisting of MRE11, RAD50 and NBN (previously described as NBS1), which is involved in DNA replication, DNA repair, and signaling to the cell cycle checkpoints. A number of kinases, like ATM (ataxia-telangiectasia mutated), ATR (ataxia-telangiectasia and Rad-3-related), and DNA PKcs (DNA protein kinase catalytic subunit), phosphorylate various protein targets in order to repair the damage. If the damage cannot be repaired, they direct the cell to apoptosis. The MRN complex as well as repair kinases are also involved in telomere maintenance and genome stability. The dysfunction of particular elements involved in the repair mechanisms leads to genome instability disorders, like ataxia telangiectasia (A-T), A-T-like disorder (ATLD) and Nijmegen breakage syndrome (NBS). The mutated genes responsible for these disorders code for proteins that play key roles in the process of DNA repair. Here we present a detailed review of current knowledge on the MRN complex, kinases engaged in DNA repair, and genome instability disorders.
authors.affiliation: Children's Memorial Health Institute, Department of Medical Genetics, Warsaw, Poland.
authors.forename: Kamila
authors.initials: K
authors.lastname: Czornak
authors.forename: Sanaullah
authors.initials: S
authors.lastname: Chughtai
authors.forename: Krystyna H
authors.initials: KH
authors.lastname: Chrzanowska
mesh_terms: D017766:Acid Anhydride Hydrolases; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000502:physiology*; D004249:DNA Damage; D004260:DNA Repair; D045643:DNA Repair Enzymes / Q000502:physiology; D004268:DNA-Binding Proteins / Q000502:physiology*; D042822:Genomic Instability; D006801:Humans; D000076228:MRE11 Homologue Protein; D008957:Models, Genetic; D009154:Mutation; D009687:Nuclear Proteins / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D016615:Telomere / Q000502:physiology; D025521:Tumor Suppressor Proteins / Q000502:physiology*
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C121766:MRE11 protein, human; C112156:NBN protein, human; D009687:Nuclear Proteins; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; D000076228:MRE11 Homologue Protein; D017766:Acid Anhydride Hydrolases; C112158:RAD50 protein, human; D045643:DNA Repair Enzymes