A Nucleotide-Analogue-Induced Gain of Function Corrects the Error-Prone Nature of Human DNA Polymerase iota
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- 作者：Amit Ketkar ; Maroof K. Zafar ; Surajit Banerjee ; Victor E. Marquez ; Martin Egli ; Robert L. Eoff
- 刊名：The Journal of the American Chemical Society
- 出版年：2012
- 出版时间：June 27, 2012
- 年：2012
- 卷：134
- 期：25
- 页码：10698-10705
- 全文大小：427K
- 年卷期：v.134,no.25(June 27, 2012)
- ISSN：1520-5126
文摘
Y-family DNA polymerases participate in replication stress and DNA damage tolerance mechanisms. The properties that allow these enzymes to copy past bulky adducts or distorted template DNA can result in a greater propensity for them to make mistakes. Of the four human Y-family members, human DNA polymerase iota (hpol鈥壩? is the most error-prone. In the current study, we elucidate the molecular basis for improving the fidelity of hpol鈥壩?through use of the fixed-conformation nucleotide North-methanocarba-2鈥?deoxyadenosine triphosphate (N-MC-dATP). Three crystal structures were solved of hpol鈥壩?in complex with DNA containing a template 2鈥?deoxythymidine (dT) paired with an incoming dNTP or modified nucleotide triphosphate. The ternary complex of hpol鈥壩?inserting N-MC-dATP opposite dT reveals that the adenine ring is stabilized in the anti orientation about the pseudo-glycosyl torsion angle, which mimics precisely the mutagenic arrangement of dGTP:dT normally preferred by hpol鈥壩? The stabilized anti conformation occurs without notable contacts from the protein but likely results from constraints imposed by the bicyclo[3.1.0]hexane scaffold of the modified nucleotide. Unmodified dATP and South-MC-dATP each adopt syn glycosyl orientations to form Hoogsteen base pairs with dT. The Hoogsteen orientation exhibits weaker base-stacking interactions and is less catalytically favorable than anti N-MC-dATP. Thus, N-MC-dATP corrects the error-prone nature of hpol鈥壩?by preventing the Hoogsteen base-pairing mode normally observed for hpol鈥壩?catalyzed insertion of dATP opposite dT. These results provide a previously unrecognized means of altering the efficiency and the fidelity of a human translesion DNA polymerase.