title: Contribution of canonical nonhomologous end joining to chromosomal rearrangements is enhanced by ATM kinase deficiency.
abstract: A likely mechanism of chromosomal rearrangement formation involves joining the ends from two different chromosomal double-strand breaks (DSBs). These events could potentially be mediated by either of two end-joining (EJ) repair pathways [canonical nonhomologous end joining (C-NHEJ) or alternative end joining (ALT-EJ)], which cause distinct rearrangement junction patterns. The relative role of these EJ pathways during rearrangement formation has remained controversial. Along these lines, we have tested whether the DNA damage response mediated by the Ataxia Telangiectasia Mutated (ATM) kinase may affect the relative influence of C-NHEJ vs. ALT-EJ on rearrangement formation. We developed a reporter in mouse cells for a 0.4-Mbp deletion rearrangement that is formed by EJ between two DSBs induced by the Cas9 endonuclease. We found that disruption of the ATM kinase causes an increase in the frequency of the rearrangement as well as a shift toward rearrangement junctions that show hallmarks of C-NHEJ. Furthermore, ATM suppresses rearrangement formation in an experimental condition, in which C-NHEJ is the predominant EJ repair event (i.e., expression of the 3' exonuclease Trex2). Finally, several C-NHEJ factors are required for the increase in rearrangement frequency caused by inhibition of the ATM kinase. We also examined ATM effectors and found that H2AX shows a similar influence as ATM, whereas the influence of ATM on this rearrangement seems independent of 53BP1. We suggest that the contribution of the C-NHEJ pathway to the formation of a 0.4-Mbp deletion rearrangement is enhanced in ATM-deficient cells.
authors.affiliation: Department of Cancer Genetics and Epigenetics, Beckman Research Institute of the City of Hope, Duarte, CA 91010.|Irell and Manella Graduate School of Biological Sciences, Beckman Research Institute of the City of Hope, Duarte, CA 91010.
authors.forename: Ragini
authors.initials: R
authors.lastname: Bhargava
authors.affiliation: Department of Cancer Genetics and Epigenetics, Beckman Research Institute of the City of Hope, Duarte, CA 91010.
authors.forename: Caree R
authors.initials: CR
authors.lastname: Carson
authors.affiliation: Department of Cancer Genetics and Epigenetics, Beckman Research Institute of the City of Hope, Duarte, CA 91010.
authors.forename: Gabriella
authors.initials: G
authors.lastname: Lee
authors.affiliation: Department of Cancer Genetics and Epigenetics, Beckman Research Institute of the City of Hope, Duarte, CA 91010; jstark@coh.org.|Irell and Manella Graduate School of Biological Sciences, Beckman Research Institute of the City of Hope, Duarte, CA 91010.
authors.forename: Jeremy M
authors.initials: JM
authors.lastname: Stark
mesh_terms: D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins / Q000172:deficiency / Q000378:metabolism; D001483:Base Sequence; D053903:DNA Breaks, Double-Stranded; D004249:DNA Damage / Q000235:genetics; D059766:DNA End-Joining Repair / Q000235:genetics*; D004720:Endonucleases / Q000378:metabolism; D015321:Gene Rearrangement / Q000235:genetics*; D006657:Histones / Q000378:metabolism; D008751:Methylene Blue / Q000378:metabolism*; D051379:Mice; D000071857:Tumor Suppressor p53-Binding Protein 1 / Q000378:metabolism
chemical_list: D006657:Histones; D000071857:Tumor Suppressor p53-Binding Protein 1; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D004720:Endonucleases; D008751:Methylene Blue
keywords: ALT-EJ; ATM; C-NHEJ; chromosomal rearrangement