Jin Chunlei, Lu Yue, Jelinek Jaroslav, Liang Shoudan, Estecio Marcos R H, Barton Michelle Craig, Issa Jean-Pierre J
The Graduate School of Biomedical Sciences, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA Department of Leukemia, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA Department of Biochemistry and Molecular Biology, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA Fels Institute for Cancer Research and Molecular Biology, Temple University, Philadelphia, PA 19140, USA.
Department of Leukemia, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA Department of Molecular Carcinogenesis, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA.
Nucleic Acids Res. 2014 Jun;42(11):6956-71. doi: 10.1093/nar/gku372. Epub 2014 May 29.
TET1 is a 5-methylcytosine dioxygenase and its DNA demethylating activity has been implicated in pluripotency and reprogramming. However, the precise role of TET1 in DNA methylation regulation outside of developmental reprogramming is still unclear. Here, we show that overexpression of the TET1 catalytic domain but not full length TET1 (TET1-FL) induces massive global DNA demethylation in differentiated cells. Genome-wide mapping reveals that 5-hydroxymethylcytosine production by TET1-FL is inhibited as DNA methylation increases, which can be explained by the preferential binding of TET1-FL to unmethylated CpG islands (CGIs) through its CXXC domain. TET1-FL specifically accumulates 5-hydroxymethylcytosine at the edges of hypomethylated CGIs, while knockdown of endogenous TET1 induces methylation spreading from methylated edges into hypomethylated CGIs. We also found that gene expression changes after TET1-FL overexpression are relatively small and independent of its dioxygenase function. Thus, our results identify TET1 as a maintenance DNA demethylase that does not purposely decrease methylation levels, but specifically prevents aberrant methylation spreading into CGIs in differentiated cells.
TET1是一种5-甲基胞嘧啶双加氧酶，其DNA去甲基化活性与多能性和重编程有关。然而，TET1在发育重编程之外的DNA甲基化调控中的精确作用仍不清楚。在这里，我们表明，TET1催化结构域的过表达而非全长TET1（TET1-FL）可诱导分化细胞中大量的全基因组DNA去甲基化。全基因组图谱显示，随着DNA甲基化增加，TET1-FL产生5-羟甲基胞嘧啶受到抑制，这可以通过TET1-FL通过其CXXC结构域优先结合未甲基化的CpG岛（CGIs）来解释。TET1-FL在低甲基化CGIs的边缘特异性积累5-羟甲基胞嘧啶，而内源性TET1的敲低则诱导甲基化从甲基化边缘扩散到低甲基化CGIs中。我们还发现，TET1-FL过表达后基因表达变化相对较小，且与其双加氧酶功能无关。因此，我们的结果确定TET1是一种维持性DNA去甲基酶，它并非有意降低甲基化水平，而是特异性地防止异常甲基化扩散到分化细胞的CGIs中。
