Szyf M, Eliasson L, Mann V, Klein G, Razin A
Proc Natl Acad Sci U S A. 1985 Dec;82(23):8090-4. doi: 10.1073/pnas.82.23.8090.
Epstein-Barr virus (EBV) producer and nonproducer cell lines have been treated with a combination of phorbol 12-myristate 13-acetate and n-butyrate (sodium salt). These inducers caused a massive hypomethylation of the EBV producer line P3HR-1 DNA (about 30%) at the time when DNA replication was inhibited. The viral DNA in these cells is heavily methylated as judged by digestion with Hpa II and probing with the Bam HI H fragment of EBV. However, upon induction with phorbol 12-myristate 13-acetate and n-butyrate, total hypomethylation of this viral DNA region was observed within 24 hr. This hypomethylation preceded EBV amplification, which became apparent only 32-36 hr after induction. When induction was carried out in the presence of retinoic acid, hypomethylation of cellular and viral DNA, viral DNA amplification, and production of the viral early antigen and viral capsid antigen were substantially inhibited. EBV DNA in another producer line (Jijoye nude) and in the nonproducer line Raji was hypomethylated and did not undergo further hypomethylation in response to induction. The observed hypomethylation of P3HR-1 and EBV DNA in the absence of DNA replication suggests that it is achieved by an active demethylation mechanism. This changes our perception of the DNA methylation phenomenon, since it has been generally accepted that hypomethylation of DNA takes place by a passive mechanism that involves DNA replication in the absence of methylation.
爱泼斯坦-巴尔病毒（EBV）产生细胞系和非产生细胞系已用佛波醇12-肉豆蔻酸酯13-乙酸酯和丁酸钠（钠盐）联合处理。这些诱导剂在抑制DNA复制时，导致EBV产生细胞系P3HR-1 DNA大量去甲基化（约30%）。用Hpa II消化并用EBV的Bam HI H片段进行探针检测表明，这些细胞中的病毒DNA高度甲基化。然而，在用佛波醇12-肉豆蔻酸酯13-乙酸酯和丁酸钠诱导后，在24小时内观察到该病毒DNA区域完全去甲基化。这种去甲基化先于EBV扩增，EBV扩增在诱导后32 - 36小时才明显出现。当在视黄酸存在下进行诱导时，细胞和病毒DNA的去甲基化、病毒DNA扩增以及病毒早期抗原和病毒衣壳抗原的产生均受到显著抑制。另一个产生细胞系（Jijoye裸鼠细胞系）和非产生细胞系Raji中的EBV DNA发生了去甲基化，并且对诱导没有进一步的去甲基化反应。在没有DNA复制的情况下观察到的P3HR-1和EBV DNA的去甲基化表明，这是通过一种主动去甲基化机制实现的。这改变了我们对DNA甲基化现象的认识，因为人们普遍认为DNA去甲基化是通过一种被动机制发生的，该机制涉及在没有甲基化的情况下进行DNA复制。
