title: Creative template-dependent synthesis by human polymerase mu.
abstract: Among the many proteins used to repair DNA double-strand breaks by nonhomologous end joining (NHEJ) are two related family X DNA polymerases, Pol λ and Pol µ. Which of these two polymerases is preferentially used for filling DNA gaps during NHEJ partly depends on sequence complementarity at the break, with Pol λ and Pol µ repairing complementary and noncomplementary ends, respectively. To better understand these substrate preferences, we present crystal structures of Pol µ on a 2-nt gapped DNA substrate, representing three steps of the catalytic cycle. In striking contrast to Pol λ, Pol µ "skips" the first available template nucleotide, instead using the template base at the 5' end of the gap to direct nucleotide binding and incorporation. This remarkable divergence from canonical 3'-end gap filling is consistent with data on end-joining substrate specificity in cells, and provides insights into polymerase substrate choices during NHEJ.
authors.affiliation: Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709.
authors.forename: Andrea F
authors.initials: AF
authors.lastname: Moon
authors.affiliation: Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709.
authors.forename: Rajendrakumar A
authors.initials: RA
authors.lastname: Gosavi
authors.affiliation: Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Kunkel
authors.affiliation: Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709 pederse2@niehs.nih.gov.
authors.forename: Lars C
authors.initials: LC
authors.lastname: Pedersen
authors.affiliation: Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Bebenek
mesh_terms: D002384:Catalysis; D018360:Crystallography, X-Ray; D004247:DNA / Q000096:biosynthesis*; D004249:DNA Damage; D019951:DNA Polymerase beta / Q000737:chemistry; D004260:DNA Repair; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D009690:Nucleic Acid Conformation; D009711:Nucleotides / Q000235:genetics; D017433:Protein Structure, Secondary; D017422:Sequence Analysis, DNA; D013379:Substrate Specificity
chemical_list: D009711:Nucleotides; D004247:DNA; C415367:DNA polymerase beta2; C407743:DNA polymerase mu; D019951:DNA Polymerase beta; D004259:DNA-Directed DNA Polymerase
keywords: DNA polymerase lambda; DNA polymerase mu; DNA repair; nonhomologous end joining