Zhang Y, Nelson M, Nietfeldt J, Xia Y, Burbank D, Ropp S, Van Etten J L
Department of Plant Pathology, University of Nebraska, Lincoln 68583-0722, USA.
Virology. 1998 Jan 20;240(2):366-75. doi: 10.1006/viro.1997.8936.
The 380-kb chlorella virus NY-2A genome is highly methylated; 45% of the cytosines are 5-methylcytosine (5mC) and 37% of the adenines are N6-methyladenine (6mA). Based on the sensitivity/resistance of NY-2A DNA to 80 methylation-sensitive DNA restriction endonucleases, the virus is predicted to encode at least 10 DNA methyltransferases: 7 6mA-specific methyltransferases, M.CviQI (GTmAC), M.CvQII (RmAR), M.CviQIII (TCGmA), M.CviQIV (GmATC), M.CviQV (TGCmA), M.CviQVI (GmANTC), and M.CviQVII (CmATG): and 3 5mC-specific methyltransferases, M.CviQVIII [RGmC(T/C/G)], M.CviQIX (mCC), and M.CviQX (mCGR). Five of the 6mA methyltransferase genes, M.CviQI, M.CviQIII, M.CviQV, M.CviQVI, and M.CviQVII, were cloned and sequenced. In addition, 2 site-specific endonuclease activities, R.CviQI (G/TAC) and NY2A-nickase (R/AG), were detected in cell-free extracts from NY-2A virus-infected chlorella. Therefore, the NY-2A genome contains at least 12 DNA methyltransferase and endonuclease genes which, altogether, compose about 3-4% of the virus genome.
380千碱基对的小球藻病毒NY - 2A基因组高度甲基化；45%的胞嘧啶是5 - 甲基胞嘧啶（5mC），37%的腺嘌呤是N6 - 甲基腺嘌呤（6mA）。基于NY - 2A DNA对80种甲基化敏感的DNA限制性内切酶的敏感性/抗性，预计该病毒编码至少10种DNA甲基转移酶：7种6mA特异性甲基转移酶，即M.CviQI（GTmAC）、M.CvQII（RmAR）、M.CviQIII（TCGmA）、M.CviQIV（GmATC）、M.CviQV（TGCmA）、M.CviQVI（GmANTC）和M.CviQVII（CmATG）；以及3种5mC特异性甲基转移酶，即M.CviQVIII [RGmC(T/C/G)]、M.CviQIX（mCC）和M.CviQX（mCGR）。6种mA甲基转移酶基因中的5种，即M.CviQI、M.CviQIII、M.CviQV、M.CviQVI和M.CviQVII，已被克隆和测序。此外，在NY - 2A病毒感染的小球藻的无细胞提取物中检测到2种位点特异性内切酶活性，即R.CviQI（G/TAC）和NY2A - 切口酶（R/AG）。因此，NY - 2A基因组包含至少12个DNA甲基转移酶和内切酶基因，它们总共约占病毒基因组的3 - 4%。
