title: The Artemis:DNA-PKcs endonuclease cleaves DNA loops, flaps, and gaps.
abstract: In eukaryotic cells, nonhomologous DNA end joining (NHEJ) is a major pathway for repair of double-strand DNA breaks (DSBs). Artemis and the 469kDa DNA-dependent protein kinase (DNA-PKcs) together form a key nuclease for NHEJ in vertebrate organisms. The structure-specific endonucleolytic activity of Artemis is activated by binding to and phosphorylation by DNA-PKcs. We tested various DNA structures in order to understand the range of structural features that are recognized by the Artemis:DNA-PKcs complex. We find that all tested substrates that contain single-to-double-strand transitions can be cleaved by the Artemis:DNA-PKcs complex near the transition region. The cleaved substrates include heterologous loops, stem-loops, flaps, and gapped substrates. Such versatile activity on single-/double-strand transition regions is important in understanding how reconstituted NHEJ systems that lack DNA polymerases can join incompatible DNA ends and yet preserve 3' overhangs. Additionally, the flexibility of the Artemis:DNA-PKcs nuclease may be important in removing secondary structures that hinder processing of DNA ends during NHEJ.
authors.affiliation: Department of Pathology, Norris Comprehensive Cancer Center, Rm. 5428, University of Southern California Keck School of Medicine, Los Angeles, CA 90089-9176, USA.
authors.forename: Yunmei
authors.initials: Y
authors.lastname: Ma
authors.forename: Klaus
authors.initials: K
authors.lastname: Schwarz
authors.forename: Michael R
authors.initials: MR
authors.lastname: Lieber
mesh_terms: D004247:DNA / Q000737:chemistry* / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000737:chemistry; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D004720:Endonucleases; D006801:Humans; D009687:Nuclear Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification; D011995:Recombination, Genetic; D013379:Substrate Specificity
chemical_list: D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D011994:Recombinant Proteins; D004247:DNA; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases; C426344:DCLRE1C protein, human; D004720:Endonucleases