期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 276, 期 6, 页码 3764-3771出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M006696200
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资金
- NCI NIH HHS [F32 CA75731, R35 CA44353] Funding Source: Medline
- NIEHS NIH HHS [P30 ES00267] Funding Source: Medline
Nucleotide insertion opposite 8-oxo-7,8-dihydroguanine (8-oxoG) by fetal calf thymus DNA polymerase delta (pol delta) was examined by steady-state and pre-steady-state rapid quench kinetic analyses. In steady-state reactions with the accessory protein proliferating cell nuclear antigen (PCNA), pol delta preferred to incorporate dCTP opposite 8- oxoG with an efficiency of incorporation an order of magnitude lower than incorporation into unmodified DNA (mainly due to an increased K-m). Pre-steady-state kinetic analysis of incorporation opposite 8-oxoG showed biphasic kinetics for incorporation of either dCTP or dATP, with rates similar to dCTP incorporation opposite G, large phosphorothioate effects (>100), and oligonucleotide dissociation apparently rate-limiting in the steady-state. Although pol delta preferred to incorporate dCTP (14% misincorporation of dATP) the extension past the A:8-oxoG mispair predominated. The presence of PCNA was found to be a more essential factor for nucleotide incorporation opposite 8-oxoG adducts than unmodified DNA, increased presteady-state rates of nucleotide incorporation by >2 orders of magnitude, and was essential for nucleotide extension beyond 8-oxoG. pol delta replication fidelity at 8-oxoG depends upon contributions from K-m,K-d(dNTP), and rates of phosphodiester bond formation, and PCNA is an important accessory protein for incorporation and extension at 8-oxoG adducts.
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