Bashtrykov Pavel, Jankevicius Gytis, Smarandache Anita, Jurkowska Renata Z, Ragozin Sergey, Jeltsch Albert
Institute of Biochemistry, Faculty of Chemistry, University Stuttgart, 70569 Stuttgart, Germany.
Chem Biol. 2012 May 25;19(5):572-8. doi: 10.1016/j.chembiol.2012.03.010.
The maintenance methylation of hemimethylated CpG sites by the DNA methyltransferase Dnmt1 is the molecular basis of the inheritance of DNA methylation patterns. Based on structural data and kinetics obtained with a truncated form of Dnmt1, an autoinhibition model for the specificity of Dnmt1 was proposed in which unmethylated DNA binds to Dnmt1's CXXC domain, which prevents its methylation. We have prepared CXXC domain variants that lost DNA binding. Corresponding full-length Dnmt1 variants did not display a reduction in specificity, indicating that the autoinhibition model does not apply in full-length Dnmt1. Furthermore, we show that the Dnmt1 M1235S variant, which carries an exchange in the catalytic domain of the enzyme, has a marked reduction in specificity, indicating that the recognition of the hemimethylated state of target sites resides within the catalytic domain.
DNA甲基转移酶Dnmt1对半甲基化CpG位点的维持性甲基化是DNA甲基化模式遗传的分子基础。基于用截短形式的Dnmt1获得的结构数据和动力学，提出了一种Dnmt1特异性的自抑制模型，其中未甲基化的DNA与Dnmt1的CXXC结构域结合，从而阻止其甲基化。我们制备了失去DNA结合能力的CXXC结构域变体。相应的全长Dnmt1变体在特异性上并未降低，这表明自抑制模型并不完全适用于全长Dnmt1。此外，我们表明，在酶的催化结构域中发生交换的Dnmt1 M1235S变体在特异性上有显著降低，这表明对靶位点半甲基化状态的识别位于催化结构域内。
