title: Exonuclease of human DNA polymerase gamma disengages its strand displacement function.
abstract: Pol γ, the only DNA polymerase found in human mitochondria, functions in both mtDNA repair and replication. During mtDNA base-excision repair, gaps are created after damaged base excision. Here we show that Pol γ efficiently gap-fills except when the gap is only a single nucleotide. Although wild-type Pol γ has very limited ability for strand displacement DNA synthesis, exo(-) (3'-5' exonuclease-deficient) Pol γ has significantly high activity and rapidly unwinds downstream DNA, synthesizing DNA at a rate comparable to that of the wild-type enzyme on a primer-template. The catalytic subunit Pol γA alone, even when exo(-), is unable to synthesize by strand displacement, making this the only known reaction of Pol γ holoenzyme that has an absolute requirement for the accessory subunit Pol γB.
authors.affiliation: Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Quan
authors.initials: Q
authors.lastname: He
authors.forename: Christie K
authors.initials: CK
authors.lastname: Shumate
authors.forename: Mark A
authors.initials: MA
authors.lastname: White
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Molineux
authors.forename: Y Whitney
authors.initials: YW
authors.lastname: Yin
mesh_terms: D001483:Base Sequence; D000074002:DNA Polymerase gamma; D004260:DNA Repair; D004272:DNA, Mitochondrial / Q000737:chemistry / Q000378:metabolism*; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D005092:Exonucleases / Q000378:metabolism*; D006801:Humans
chemical_list: D004272:DNA, Mitochondrial; D000074002:DNA Polymerase gamma; D004259:DNA-Directed DNA Polymerase; D005092:Exonucleases
keywords: DNA repair and replication; Molecular motor; Strand displacement