title: Differences in the recruitment of DNA repair proteins at subtelomeric and interstitial I-SceI endonuclease-induced DNA double-strand breaks.
abstract: Telomeres are nucleoprotein structures that are required to protect chromosome ends. Dysfunctional telomeres are recognized as DNA double-strand breaks (DSBs), and elicit the activation of a DNA damage response (DDR). We have previously reported that DSBs near telomeres are poorly repaired, resulting in a high frequency of large deletions and gross chromosome rearrangements (GCRs). Our previous genetic studies have demonstrated that this sensitivity of telomeric regions to DSBs is a result of excessive processing. In the current study, we have further investigated the sensitivity of telomeric regions to DSBs through the analysis of repair proteins associated with DSBs at interstitial and telomeric sites. Following the inducible expression of I-SceI endonuclease, chromatin immunoprecipitation (ChIP) and real-time quantitative PCR were used to compare the recruitment of repair proteins at I-SceI-induced DSBs at interstitial and subtelomeric sites. We observed that proteins that are specifically associated with processing of DSBs during homologous recombination repair, RAD51, BRCA1, and CtIP, are present at a much greater abundance at subtelomeric DSBs. In contrast, Ku70, which is specifically involved in classical nonhomologous end joining, showed no difference at interstitial and subtelomeric DSBs. Importantly, ATM was lower in abundance at subtelomeric DSBs, while ATR was in greater abundance at subtelomeric DSBs, consistent with the accumulation of processed DSBs near telomeres, since processing is accompanied by a transition from ATM to ATR binding. Combined, our results suggest that excessive processing is responsible for the increased frequency of large deletions and GCRs at DSBs near telomeres.
authors.affiliation: Department of Radiation Oncology, University of California, San Francisco, 2340 Sutter St. San Francisco, CA 94143-1330, USA.
authors.forename: Bárbara
authors.initials: B
authors.lastname: Alcaraz Silva
authors.affiliation: Department of Radiation Oncology, University of California, San Francisco, 2340 Sutter St. San Francisco, CA 94143-1330, USA.
authors.forename: Trevor J
authors.initials: TJ
authors.lastname: Jones
authors.affiliation: Department of Radiation Oncology, University of California, San Francisco, 2340 Sutter St. San Francisco, CA 94143-1330, USA. Electronic address: John.Murnane@ucsf.edu.
authors.forename: John P
authors.initials: JP
authors.lastname: Murnane
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D019313:BRCA1 Protein / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded; D059766:DNA End-Joining Repair; D004706:Endodeoxyribonucleases; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism; D051135:Rad51 Recombinase / Q000378:metabolism; D059767:Recombinational DNA Repair; D017384:Sequence Deletion; D016615:Telomere / Q000378:metabolism*
chemical_list: D019313:BRCA1 Protein; C492913:BRCA1 protein, human; D002352:Carrier Proteins; D009687:Nuclear Proteins; D004247:DNA; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C495153:RAD51 protein, human; D051135:Rad51 Recombinase; D004706:Endodeoxyribonucleases; C410741:RBBP8 protein, human
keywords: DNA repair; Double-strand breaks; Telomere