Excision of 5-hydroxymethyluracil and 5-carboxylcytosine by the thymine DNA glycosylase domain: its structural basis and implications for active DNA demethylation.
Excision of 5-hydroxymethyluracil and 5-carboxylcytosine by the thymine DNA glycosylase domain: its structural basis and implications for active DNA demethylation.
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DOI：
10.1093/nar/gks845
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发表时间：
2012-11-01
影响因子：
14.9
通讯作者：
Cheng X
中科院分区：
文献类型：
--
作者：
Hashimoto H;Hong S;Bhagwat AS;Zhang X;Cheng X
哺乳动物胸腺嘧啶DNA糖基化酶（TDG）通过碱基切除修复途径参与主动DNA去甲基化。TDG从G：X错配中切除错配碱基，其中X是尿嘧啶、胸腺嘧啶或5-羟甲基尿嘧啶（5 hmU）。它们分别是胞嘧啶、5-甲基胞嘧啶（5 mC）和5-羟甲基胞嘧啶（5 hmC）的脱氨基产物。此外，当与鸟嘌呤配对时，TDG切除泰特蛋白产物5-甲酰基胞嘧啶（5 fC）和5-羧基胞嘧啶（5caC），但不切除5 hmC和5 mC。在这里，我们提出了一个后反应的复杂结构的人TDG域与28个碱基对的DNA含有G：5 hmU错配。TDG从双链DNA翻转靶核苷酸，切割N-糖苷键，并使C1′水解的脱碱基糖处于翻转状态。切割的5 hmU碱基保留在酶的结合口袋中。TDG允许与基于T/U（5 hmU）和基于C（5caC）的修饰进行氢键相互作用，从而使其能够在更广泛的底物上发挥活性。我们进一步表明，TDG催化结构域在较低的pH值（5.5）具有较高的活性为5caC相比，在较高的pH值（7.5和8.0）的活动，结构相关的大肠杆菌错配尿嘧啶糖基化酶可以切除5caC以及。我们讨论了几种可能的机制，包括氨基-亚氨基互变异构的基板基地，可以解释如何TDG歧视对5 hmC和5 mC。
The mammalian thymine DNA glycosylase (TDG) is implicated in active DNA demethylation via the base excision repair pathway. TDG excises the mismatched base from G:X mismatches, where X is uracil, thymine or 5-hydroxymethyluracil (5hmU). These are, respectively, the deamination products of cytosine, 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC). In addition, TDG excises the Tet protein products 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC) but not 5hmC and 5mC, when paired with a guanine. Here we present a post-reactive complex structure of the human TDG domain with a 28-base pair DNA containing a G:5hmU mismatch. TDG flips the target nucleotide from the double-stranded DNA, cleaves the N-glycosidic bond and leaves the C1′ hydrolyzed abasic sugar in the flipped state. The cleaved 5hmU base remains in a binding pocket of the enzyme. TDG allows hydrogen-bonding interactions to both T/U-based (5hmU) and C-based (5caC) modifications, thus enabling its activity on a wider range of substrates. We further show that the TDG catalytic domain has higher activity for 5caC at a lower pH (5.5) as compared to the activities at higher pH (7.5 and 8.0) and that the structurally related Escherichia coli mismatch uracil glycosylase can excise 5caC as well. We discuss several possible mechanisms, including the amino-imino tautomerization of the substrate base that may explain how TDG discriminates against 5hmC and 5mC.
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影响因子：
64.5
作者：
Bhutani N;Burns DM;Blau HM
通讯作者：
Blau HM
影响因子：
3.7
作者：
Globisch D;Münzel M;Müller M;Michalakis S;Wagner M;Koch S;Brückl T;Biel M;Carell T
通讯作者：
Carell T
DOI：
10.1107/s0907444904019158
发表时间：
2004-12-01
影响因子：
2.2
作者：
Emsley, P;Cowtan, K
通讯作者：
Cowtan, K
影响因子：
5.1
作者：
Hang, Bo;Guhaev, Anton B.
通讯作者：
Guhaev, Anton B.
影响因子：
7.3
作者：
HANSCH, C;LEO, A;LIEN, EJ
通讯作者：
LIEN, EJ