title: On-off regulation of 3' exonuclease excision to DNA polymerization by Exo+ polymerase.
abstract: The role of 3' exonuclease excision in DNA polymerization was evaluated in primer extensions using 3' allele-specific primers that had exonuclease-digestible and exonuclease-resistant 3' termini. With exonuclease-digestible unmodified 3' mismatched primers, the exo+ polymerase yielded template-dependent products. Using exonuclease-resistant 3' mismatched primers, no primer-extended product resulted from exo+ polymerase. As a control, polymerase without proofreading activity yielded primer-dependent products from 3' mismatched primers. These data indicated that a successful removal of the mismatch is required for DNA polymerization from the 3' mismatched primers by exo+ polymerase. In addition to the well-known proofreading from this mismatch removal, the premature termination in DNA polymerization, due to the failure of the efficient removal of the mismatched nucleotides, worked as an off-switch in maintaining the high fidelity in DNA replication from exo+ polymerase.
authors.affiliation: Institute of Biotechnology, Institute of Pharmacy and Pharmacology, Nanhua University, Hengyang 421001, China.
authors.forename: Jia
authors.initials: J
authors.lastname: Zhang
authors.forename: Kai
authors.initials: K
authors.lastname: Li
mesh_terms: D001483:Base Sequence; D001704:Biopolymers; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D005092:Exonucleases / Q000378:metabolism*; D008969:Molecular Sequence Data
chemical_list: D001704:Biopolymers; D004247:DNA; D004259:DNA-Directed DNA Polymerase; D005092:Exonucleases; C022650:spleen exonuclease