title: Bridging of double-stranded breaks by the nonhomologous end-joining ligation complex is modulated by DNA end chemistry.
abstract: The nonhomologous end-joining (NHEJ) pathway is the primary repair pathway for DNA double strand breaks (DSBs) in humans. Repair is mediated by a core complex of NHEJ factors that includes a ligase (DNA Ligase IV; L4) that relies on juxtaposition of 3΄ hydroxyl and 5΄ phosphate termini of the strand breaks for catalysis. However, chromosome breaks arising from biological sources often have different end chemistries, and how these different end chemistries impact the way in which the core complex directs the necessary transitions from end pairing to ligation is not known. Here, using single-molecule FRET (smFRET), we show that prior to ligation, differences in end chemistry strongly modulate the bridging of broken ends by the NHEJ core complex. In particular, the 5΄ phosphate group is a recognition element for L4 and is critical for the ability of NHEJ factors to promote stable pairing of ends. Moreover, other chemical incompatibilities, including products of aborted ligation, are sufficient to disrupt end pairing. Based on these observations, we propose a mechanism for iterative repair of DSBs by NHEJ.
authors.affiliation: New York University School of Medicine, Department of Biochemistry and Molecular Pharmacology, New York, NY 10016, USA.
authors.forename: Dylan A
authors.initials: DA
authors.lastname: Reid
authors.affiliation: University of North Carolina School of Medicine, Curriculum in Genetics and Molecular Biology and Department of Biochemistry and Biophysics, Chapel Hill, NC 27599, USA.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Conlin
authors.affiliation: New York University School of Medicine, Department of Biochemistry and Molecular Pharmacology, New York, NY 10016, USA.
authors.forename: Yandong
authors.initials: Y
authors.lastname: Yin
authors.affiliation: University of Southern California Keck School of Medicine, Norris Comprehensive Cancer Center, Los Angeles, CA 90033, USA.
authors.forename: Howard H
authors.initials: HH
authors.lastname: Chang
authors.affiliation: University of Southern California Keck School of Medicine, Norris Comprehensive Cancer Center, Los Angeles, CA 90033, USA.
authors.forename: Go
authors.initials: G
authors.lastname: Watanabe
authors.affiliation: University of Southern California Keck School of Medicine, Norris Comprehensive Cancer Center, Los Angeles, CA 90033, USA.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Lieber
authors.affiliation: University of North Carolina School of Medicine, Curriculum in Genetics and Molecular Biology and Department of Biochemistry and Biophysics, Chapel Hill, NC 27599, USA.
authors.forename: Dale A
authors.initials: DA
authors.lastname: Ramsden
authors.affiliation: New York University School of Medicine, Department of Biochemistry and Molecular Pharmacology, New York, NY 10016, USA.
authors.forename: Eli
authors.initials: E
authors.lastname: Rothenberg
mesh_terms: D000818:Animals; D004247:DNA / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D053903:DNA Breaks, Double-Stranded; D059766:DNA End-Joining Repair; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000378:metabolism*; D008954:Models, Biological; D011485:Protein Binding
chemical_list: D004268:DNA-Binding Proteins; D004247:DNA