title: Characterization of an NBS1 C-terminal peptide that can inhibit ataxia telangiectasia mutated (ATM)-mediated DNA damage responses and enhance radiosensitivity.
abstract: ATM and NBS1, mutation of which lead to the human autosomal recessive diseases ataxia telangiectasia and Nijmegen breakage syndrome (NBS), respectively, are essential elements in the cellular response to DNA damage induced by ionizing radiation (IR). ATM is a member of the phosphatidylinositol 3-kinase family and is activated by IR in an NBS1-dependent manner. The extreme C terminus of NBS1 contains an evolutionarily conserved sequence motif that is critical for binding to and activation of ATM after IR. ATM phosphorylates a series of targets to initiate cell cycle arrest and promote cell survival in response to DNA damage. Therefore, targeting the NBS1-ATM interaction may lead to a novel approach for specific ATM inhibition and radiosensitization. We developed small peptides containing the conserved C-terminal sequence of NBS1 to investigate whether these peptides can interfere with the DNA damage pathway. We found that wild-type NBS1 inhibitory peptides (wtNIP) can abrogate NBS1-ATM association in the presence or absence of IR. We also found that cells exposed to wtNIP displayed a significant reduction in radiation-induced gamma-H2AX and NBS1 focus formation compared with cells treated with control peptides, demonstrating that wtNIP possesses a strong inhibitory effect on ATM. The inhibitory effect of wtNIP also leads to a significant decrease in clonogenic survival in response to IR. Furthermore, wtNIP does not radiosensitize cells with defective ATM, suggesting a specific inhibition of ATM. Together, these data provide a proof of principle for the use of NBS1 C-terminal small peptides as specific ATM inhibitors and radiosensitizers.
authors.affiliation: Department of Biochemistry and Molecular Biology, Southern Research Institute, Birmingham, AL 35205, USA.
authors.forename: Mickael J
authors.initials: MJ
authors.lastname: Cariveau
authors.forename: Xi
authors.initials: X
authors.lastname: Tang
authors.forename: Xiao-Li
authors.initials: XL
authors.lastname: Cui
authors.forename: Bo
authors.initials: B
authors.lastname: Xu
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D020134:Catalytic Domain; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004249:DNA Damage; D051747:DNA-Activated Protein Kinase / Q000502:physiology; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006367:HeLa Cells; D006657:Histones / Q000378:metabolism; D006801:Humans; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors*; D010446:Peptide Fragments / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D025521:Tumor Suppressor Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C468783:H2AX protein, human; D006657:Histones; C112156:NBN protein, human; D009687:Nuclear Proteins; D010446:Peptide Fragments; D011838:Radiation-Sensitizing Agents; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D051747:DNA-Activated Protein Kinase; D017346:Protein Serine-Threonine Kinases