State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, China.
Nat Struct Mol Biol. 2012 Jun 3;19(7):671-6. doi: 10.1038/nsmb.2320.
ALKBH2 is a direct DNA repair dioxygenase guarding the mammalian genome against N(1)-methyladenine, N(3)-methylcytosine and 1,N(6)-ethenoadenine damage. A prerequisite for repair is to identify these lesions in the genome. Here we present crystal structures of human ALKBH2 bound to different duplex DNAs. Together with computational and biochemical analyses, our results suggest that DNA interrogation by ALKBH2 has two previously unknown features: (i) ALKBH2 probes base-pair stability and detects base pairs with reduced stability, and (ii) ALKBH2 does not have nor need a damage-checking site, which is critical for preventing spurious base cleavage for several glycosylases. The demethylation mechanism of ALKBH2 insures that only cognate lesions are oxidized and reversed to normal bases, and that a flipped, non-substrate base remains intact in the active site. Overall, the combination of duplex interrogation and oxidation chemistry allows ALKBH2 to detect and process diverse lesions efficiently and correctly.
ALKBH2 是一种直接的 DNA 修复双氧酶，可保护哺乳动物基因组免受 N(1)-甲基腺嘌呤、N(3)-甲基胞嘧啶和 1,N(6)-乙烯腺嘌呤的损伤。修复的前提是在基因组中识别这些损伤。在这里，我们展示了与人 ALKBH2 结合的不同双链 DNA 的晶体结构。通过计算和生化分析，我们的结果表明，ALKBH2 对 DNA 的检测具有两个以前未知的特征：(i) ALKBH2 探测碱基对稳定性并检测稳定性降低的碱基对，和 (ii) ALKBH2 没有也不需要损伤检查位点，这对于防止几个糖苷酶的错误碱基切割至关重要。ALKBH2 的去甲基化机制确保只有同源损伤被氧化并恢复为正常碱基，并且翻转的、非底物碱基在活性位点中保持完整。总的来说，双链体检测和氧化化学的结合允许 ALKBH2 高效且正确地检测和处理各种损伤。
