Xia Y N, Van Etten J L
Mol Cell Biol. 1986 May;6(5):1440-5. doi: 10.1128/mcb.6.5.1440-1445.1986.
A DNA methyltransferase was isolated from a eucaryotic, Chlorella-like green alga infected with the virus PBCV-1. The enzyme recognized the sequence GATC and methylated deoxyadenosine solely in GATC sequences. Host DNA, which contains GATC sequences, but not PBCV-1 DNA, which contains GmATC sequences, was a good substrate for the enzyme in vitro. The DNA methyltransferase activity was first detected about 1 h after viral infection; PBCV-1 DNA synthesis and host DNA degradation also began at about this time. The appearance of the DNA methyltransferase activity required de novo protein synthesis, and the enzyme was probably virus encoded. Methylation of DNAs with the PBCV-1-induced methyltransferase conferred resistance of the DNAs to a PBCV-1-induced restriction endonuclease enzyme described previously (Y. Xia, D. E. Burbank, L. Uher, D. Rabussay, and J. L. Van Etten, Mol. Cell. Biol. 6:1430-1439). We propose that the PBCV-1-induced methyltransferase protects viral DNA from the PBCV-1-induced restriction endonuclease and is part of a virus-induced restriction and modification system in PBCV-1-infected Chlorella cells.
从感染病毒PBCV - 1的真核类小球藻绿藻中分离出一种DNA甲基转移酶。该酶识别序列GATC，并仅在GATC序列中使脱氧腺苷甲基化。含有GATC序列的宿主DNA是该酶在体外的良好底物，但含有GmATC序列的PBCV - 1 DNA则不是。DNA甲基转移酶活性在病毒感染后约1小时首次检测到；PBCV - 1 DNA合成和宿主DNA降解也大约在此时开始。DNA甲基转移酶活性的出现需要从头合成蛋白质，该酶可能由病毒编码。用PBCV - 1诱导的甲基转移酶对DNA进行甲基化，可使DNA对先前描述的PBCV - 1诱导的限制性内切酶产生抗性（Y. Xia、D. E. Burbank、L. Uher、D. Rabussay和J. L. Van Etten，《分子细胞生物学》6:1430 - 1439）。我们提出，PBCV - 1诱导的甲基转移酶可保护病毒DNA免受PBCV - 1诱导的限制性内切酶的作用，并且是PBCV - 1感染的小球藻细胞中病毒诱导的限制与修饰系统的一部分。
