title: Mechanism of somatic hypermutation at the WA motif by human DNA polymerase η.
abstract: 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 η (Pol η) 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 η 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 η. Weak base paring of the W (T:A or A:T) at the primer end and their distinct interactions with Pol η 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 η can extend the T:G mispair efficiently to complete the mutagenesis.
authors: Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou 310029, China.
authors: Ye
authors: Y
authors: Zhao
authors: Mark T
authors: MT
authors: Gregory
authors: Christian
authors: C
authors: Biertümpfel
authors: Yue-Jin
authors: YJ
authors: Hua
authors: Fumio
authors: F
authors: Hanaoka
authors: Wei
authors: W
authors: Yang
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry; D020816:Amino Acid Motifs; D002412:Cations; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry*; D003848:Deoxyguanine Nucleotides / Q000737:chemistry; D006801:Humans; D007136:Immunoglobulins / Q000737:chemistry; D007700:Kinetics; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009690:Nucleic Acid Conformation; D027041:Somatic Hypermutation, Immunoglobulin; D000099270:Y-Family DNA Polymerases
chemical_list: D000255:Adenosine Triphosphate; D002412:Cations; D004259:DNA-Directed DNA Polymerase; D003848:Deoxyguanine Nucleotides; D007136:Immunoglobulins; C029603:deoxyguanosine triphosphate; C112338:Rad30 protein; D000099270:Y-Family DNA Polymerases
keywords: A-to-G transition; immunoglobulin; π–cation stacking
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