title: Abasic template lesions are strong chain terminators for DNA primase but not for DNA polymerase alpha during the synthesis of new DNA strands.
abstract: The effects of abasic lesions on both primase activity and DNA polymerase alpha- (pol alpha) catalyzed elongation of primase-synthesized primers were examined. Abasic lesions were strong chain terminators during primer synthesis by primase. However, extension of primase-synthesized primers by pol alpha resulted in 60-93% bypass of abasic lesions. Sequencing of bypass products generated during this primase-coupled pol alpha activity showed that dAMP was preferentially incorporated opposite the abasic lesion, indicating that pol alpha was responsible for bypass. In contrast, previous analyses of pol alpha-catalyzed elongation of exogenously supplied DNA primer-templates showed that abasic lesions strongly terminated DNA synthesis. Thus, elongation of primase-synthesized primers by pol alpha-primase is fundamentally different than elongation of exogenously added primer-templates with respect to interaction with abasic lesions. Furthermore, this high level of abasic lesion bypass during primase-coupled pol alpha activity provides an additional mechanism for how translesional synthesis may occur in vivo, an event hypothesized to be mutagenic.
authors.affiliation: Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, USA.
authors.forename: L K
authors.initials: LK
authors.lastname: Zerbe
authors.forename: M F
authors.initials: MF
authors.lastname: Goodman
authors.forename: E
authors.initials: E
authors.lastname: Efrati
authors.forename: R D
authors.initials: RD
authors.lastname: Kuchta
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000138:chemical synthesis*; D004256:DNA Polymerase I / Q000378:metabolism*; D019915:DNA Primase / Q000378:metabolism*; D017931:DNA Primers; D013698:Templates, Genetic
chemical_list: D017931:DNA Primers; D004247:DNA; D019915:DNA Primase; D004256:DNA Polymerase I