Suetake Isao, Morimoto Yuuki, Fuchikami Takuya, Abe Kuniya, Tajima Shoji
Laboratory of Epigenetics, Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871.
J Biochem. 2006 Oct;140(4):553-9. doi: 10.1093/jb/mvj185. Epub 2006 Aug 31.
Quantification of DNA methyltransferases Dnmt3a and Dnmt3a2, and Dnmt3L in isolated male gonocytes in day 16.5 embryos confirmed that not Dnmt3a but Dnmt3a2 and Dnmt3L were the major Dnmt3s. The expression level of Dnmt3L constituted 5- to 10-fold molar excess compared to that of Dnmt3a2. The stimulation property of the DNA methylation activity of Dnmt3a2 with Dnmt3L towards substrate DNA in naked or nucleosomes was similar to that of Dnmt3a. However, the DNA methylation activity of not Dnmt3a but Dnmt3a2 was severely inhibited at the physiological salt concentration. Interestingly, the activity of Dnmt3a2 was significantly detected in the presence of Dnmt3L even at the physiological salt concentration. This indicates that Dnmt3a2 functions only in the presence of Dnmt3L in male gonocytes, and may explain why Dnmt3L is required specifically in mouse gonocytes for DNA methylation.
对16.5天胚胎中分离出的雄性生殖母细胞中的DNA甲基转移酶Dnmt3a、Dnmt3a2和Dnmt3L进行定量分析，结果证实主要的Dnmt3不是Dnmt3a，而是Dnmt3a2和Dnmt3L。与Dnmt3a2相比，Dnmt3L的表达水平在摩尔数上高出5至10倍。Dnmt3L对Dnmt3a2的DNA甲基化活性在裸DNA或核小体中对底物DNA的刺激特性与Dnmt3a相似。然而，在生理盐浓度下，主要是Dnmt3a2而非Dnmt3a的DNA甲基化活性受到严重抑制。有趣的是，即使在生理盐浓度下，在存在Dnmt3L的情况下也能显著检测到Dnmt3a2的活性。这表明Dnmt3a2仅在雄性生殖母细胞中存在Dnmt3L时发挥作用，这可能解释了为什么在小鼠生殖母细胞中DNA甲基化特别需要Dnmt3L。
