Ring-Opening of the 纬-OH-PdG Adduct Promotes Error-Free Bypass by the Sulfolobus solfataricus DNA Polymerase Dpo4
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- 作者：Ganesh Shanmugam ; Irina G. Minko ; Surajit Banerjee ; Plamen P. Christov ; Ivan D. Kozekov ; Carmelo J. Rizzo ; R. Stephen Lloyd ; Martin Egli ; Michael P. Stone
- 刊名：Chemical Research in Toxicology
- 出版年：2013
- 出版时间：September 16, 2013
- 年：2013
- 卷：26
- 期：9
- 页码：1348-1360
- 全文大小：841K
- 年卷期：v.26,no.9(September 16, 2013)
- ISSN：1520-5010
文摘
Acrolein, a mutagenic aldehyde, reacts with deoxyguanosine (dG) to form 3-(2鈥?deoxy-尾-d-erythro-pentofuranosyl)-5,6,7,8-tetrahydro-8-hydroxypyrimido[1,2-a] purin-10(3H)-one (纬-OH-PdG). When placed opposite deoxycytosine (dC) in DNA, 纬-OH-PdG undergoes ring-opening to the N2-(3-oxopropyl)-dG. Ring-opening of the adduct has been hypothesized to facilitate nonmutagenic bypass, particularly by DNA polymerases of the Y family. This study examined the bypass of 纬-OH-PdG by Sulfolobus solfataricus Dpo4, the prototypic Y-family DNA polymerase, using templates that contained the adduct in either the 5鈥?CXG-3鈥?or the 5鈥?TXG-3鈥?sequence context. Although 纬-OH-PdG partially blocked Dpo4-catalyzed DNA synthesis, full primer extension was observed, and the majority of bypass products were error-free. Conversion of the adduct into an irreversibly ring-opened derivative prior to reaction facilitated bypass and further improved the fidelity. Structures of ternary Dpo4路DNA路dNTP complexes were determined with primers that either were positioned immediately upstream of the lesion (preinsertion complexes) or had a 3鈥?terminal dC opposite the lesion (postinsertion complexes); the incoming nucleotides, either dGTP or dATP, were complementary to the template 5鈥?neighbor nucleotide. In both postinsertion complexes, the adduct existed as ring-opened species, and the resulting base-pair featured Watson鈥揅rick hydrogen bonding. The incoming nucleotide paired with the 5鈥?neighbor template, while the primer 3鈥?hydroxyl was positioned to facilitate extension. In contrast, 纬-OH-PdG was in the ring-closed form in both preinsertion complexes, and the overall structure did not favor catalysis. These data provide insights into 纬-OH-PdG chemistry during replication bypass by the Dpo4 DNA polymerase and may explain why 纬-OH-PdG-induced mutations due to primer鈥搕emplate misalignment are uncommon.