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标题：Mechanism of somatic hypermutation at the WA motif by human DNA polymerase η
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作者：Ye Zhao ; Mark T. Gregory ; Christian Biertümpfel 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2013
卷号：110
期号：20
页码：8146-8151
DOI：10.1073/pnas.1303126110
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Somatic hypermutation is programmed base substitutions in the variable regions of Ig genes for high-affinity antibody generation. Two motifs, RGYW and WA (R, purine; Y, pyrimidine; W, A or T), have been found to be somatic hypermutation hotspots. Overwhelming evidence suggests that DNA polymerase {eta} (Pol {eta}) is responsible for converting the WA motif to WG by misincorporating dGTP opposite the templating T. To elucidate the molecular mechanism, crystal structures and kinetics of human Pol {eta} substituting dGTP for dATP in four sequence contexts, TA, AA, GA, and CA, have been determined and compared. The T:dGTP wobble base pair is stabilized by Gln-38 and Arg-61, two uniquely conserved residues among Pol {eta}. Weak base paring of the W (T:A or A:T) at the primer end and their distinct interactions with Pol {eta} lead to misincorporation of G in the WA motif. Between two WA motifs, our kinetic and structural data indicate that A-to-G mutation occurs more readily in the TA context than AA. Finally, Pol {eta} can extend the T:G mispair efficiently to complete the mutagenesis.
关键词：π–cation stacking ; A-to-G transition ; immunoglobulin