Hattman S
J Virol. 1972 Sep;10(3):356-61. doi: 10.1128/JVI.10.3.356-361.1972.
The N(6)-methyladenine (MeAde) and 5-methylcytosine (MeC) contents in deoxyribonucleic acid (DNA) of bacteriophage lambda has been analyzed as a function of host specificity. The following facts have emerged: (i) lambda grown on strains harboring the P1 prophage contain ca. 70 more MeAde residues/DNA molecule than lambda grown either in the P1-sensitive parent, or in a P1 immune-defective lysogen which does not confer P1 modification; (ii) lambda grown on strains harboring the N-3 drug-resistance factor contain ca. 60 more MeC residues/DNA molecule than lambda grown on the parental strain lacking the factor; (iii) lambda grown in Escherichia coli B strains is devoid of MeC, whereas lambda grown in a B (N-3) host contains a high level of MeC; (iv) the MeAde content in lambda DNA is not affected by the N-3 factor. These results suggest that P1 controls an adenine-specific DNA methylase, and that the N-3 plasmid controls a cytosine-specific DNA methylase. The N-3 factor has been observed previously to direct cytosine-specific methylation of phage P22 DNA and E. coli B DNA in vivo; in vitro studies presented here demonstrate this activity.
已对噬菌体λ脱氧核糖核酸（DNA）中的N⁶-甲基腺嘌呤（MeAde）和5-甲基胞嘧啶（MeC）含量作为宿主特异性的函数进行了分析。出现了以下事实：（i）在携带P1原噬菌体的菌株上生长的λ，每个DNA分子含有的MeAde残基比在P1敏感亲本或不赋予P1修饰的P1免疫缺陷溶原菌中生长的λ多约70个；（ii）在携带N-3耐药因子的菌株上生长的λ，每个DNA分子含有的MeC残基比在缺乏该因子的亲本菌株上生长的λ多约60个；（iii）在大肠杆菌B菌株中生长的λ不含MeC，而在B（N-3）宿主中生长的λ含有高水平的MeC；（iv）λ DNA中的MeAde含量不受N-3因子的影响。这些结果表明，P1控制一种腺嘌呤特异性DNA甲基化酶，并且N-3质粒控制一种胞嘧啶特异性DNA甲基化酶。先前已观察到N-3因子在体内指导噬菌体P22 DNA和大肠杆菌B DNA的胞嘧啶特异性甲基化；此处给出的体外研究证明了这种活性。
