The role of DNA replication machinery in maintenance of DNA methylation

在DNA复制过程中，DNA甲基化模式的忠实传播对于维持单个分化细胞的细胞表型至关重要。然而，目前尚不清楚DNA甲基化的维持和DNA复制是如何协调的。利用非洲爪哇卵提取液，我们成功地在体外复制了维持DNA甲基化。我们发现uhrf1具有泛素化组蛋白H3的活性。DNMT1将半甲基DNA转化为全甲基DNA，在体外通过复制焦点靶向序列优先与泛素化的组蛋白H3结合。我们还表明，uhrf1的泛素连接酶活性对于Dnmt1在DNA复制位置的募集和维持哺乳动物培养细胞中的DNA甲基化是必不可少的。我们的发现首次证明了DNA甲基化和DNA复制之间通过组蛋白H3泛素化的机制联系。

Faithful propagation of DNA methylation patterns during DNA replication is critical for maintaining cellular phenotypes of individual differentiated cells. However, it is unclear how the maintenance of DNA methylation and DNA replication is coordinated. Using Xenopus egg extracts, we successfully reproduce maintenance DNA methylation in vitro. We found that Uhrf1 has an activity to ubiquitylate histone H3. Dnmt1, which converts hemi-methyl DNA to full-methyl DNA, preferentially associates with ubiquitylated histone H3 in vitro through a region previously identified as a replication foci targeting sequence. We also show that ubiquitin ligase activity of Uhrf1 is essential for Dnmt1 recruitment to DNA replication sites and maintaining DNA methylation in mammalian cultured cells. Our finding represent the first evidence of the mechanistic link between DNA methylation and DNA replication through histone H3 ubiquitylation.