title: Alternative-NHEJ is a mechanistically distinct pathway of mammalian chromosome break repair.
abstract: Characterizing the functional overlap and mutagenic potential of different pathways of chromosomal double-strand break (DSB) repair is important to understand how mutations arise during cancer development and treatment. To this end, we have compared the role of individual factors in three different pathways of mammalian DSB repair: alternative-nonhomologous end joining (alt-NHEJ), single-strand annealing (SSA), and homology directed repair (HDR/GC). Considering early steps of repair, we found that the DSB end-processing factors KU and CtIP affect all three pathways similarly, in that repair is suppressed by KU and promoted by CtIP. In contrast, both KU and CtIP appear dispensable for the absolute level of total-NHEJ between two tandem I-SceI-induced DSBs. During later steps of repair, we find that while the annealing and processing factors RAD52 and ERCC1 are important to promote SSA, both HDR/GC and alt-NHEJ are significantly less dependent upon these factors. As well, while disruption of RAD51 causes a decrease in HDR/GC and an increase in SSA, inhibition of this factor did not affect alt-NHEJ. These results suggest that the regulation of DSB end-processing via KU/CtIP is a common step during alt-NHEJ, SSA, and HDR/GC. However, at later steps of repair, alt-NHEJ is a mechanistically distinct pathway of DSB repair, and thus may play a unique role in mutagenesis during cancer development and therapy.
authors.affiliation: Department of Radiation Biology, Beckman Research Institute of City of Hope, Duarte, California, United States of America.
authors.forename: Nicole
authors.initials: N
authors.lastname: Bennardo
authors.forename: Anita
authors.initials: A
authors.lastname: Cheng
authors.forename: Nick
authors.initials: N
authors.lastname: Huang
authors.forename: Jeremy M
authors.initials: JM
authors.lastname: Stark
mesh_terms: D000818:Animals; D034961:Antigens, Nuclear / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D019457:Chromosome Breakage; D033481:Chromosomes, Mammalian / Q000235:genetics*; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015252:Deoxyribonucleases, Type II Site-Specific / Q000235:genetics / Q000378:metabolism; D004706:Endodeoxyribonucleases; D004720:Endonucleases / Q000235:genetics / Q000378:metabolism; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D000072200:Ku Autoantigen; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D051135:Rad51 Recombinase / Q000235:genetics / Q000378:metabolism; D051721:Rad52 DNA Repair and Recombination Protein / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins
chemical_list: D034961:Antigens, Nuclear; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D051721:Rad52 DNA Repair and Recombination Protein; D029701:Saccharomyces cerevisiae Proteins; D049452:Green Fluorescent Proteins; D051135:Rad51 Recombinase; C071447:ERCC1 protein, human; D004706:Endodeoxyribonucleases; D004720:Endonucleases; C410741:RBBP8 protein, human; C037725:SCEI protein, S cerevisiae; D015252:Deoxyribonucleases, Type II Site-Specific; C000606509:Xrcc6 protein, human; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen