Cregg J M, Nguyen A H, Ito J
Gene. 1980 Dec;12(1-2):17-24. doi: 10.1016/0378-1119(80)90011-6.
The DNA of the Bacillus subtilis temperate phage phi 3T is not susceptible to cleavage by the restriction endonuclease HaeIII, although it is cut by many other restriction enzymes. The host DNA from uninfected cells is cut by HaeIII. We show that phi 3T DNA propagated in a restriction-modification-defective Escherichia coli cell can be digested by HaeIII. Thus, phi 3T DNA does contain the nucleotide recognition sequence of HaeIII. We suggest that this phage induces the modification of its own DNA. In support of this mechanism we show that extracts prepared from phi 3T-infected cells contain an activity which in the presence of S-adenosyl-L-methionine (SAM) can modify lambda DNA against cleavage by HaeIII. The same in vitro-modified DNA is still susceptible to cleavage by other restriction endonucleases.
枯草芽孢杆菌温和噬菌体φ3T的DNA不易被限制性内切酶HaeIII切割，尽管它能被许多其他限制性酶切割。未感染细胞的宿主DNA能被HaeIII切割。我们发现，在限制修饰缺陷型大肠杆菌细胞中繁殖的φ3T DNA能被HaeIII消化。因此，φ3T DNA确实含有HaeIII的核苷酸识别序列。我们推测这种噬菌体诱导了其自身DNA的修饰。为支持这一机制，我们发现从感染φ3T的细胞中制备的提取物含有一种活性，在S-腺苷-L-甲硫氨酸（SAM）存在的情况下，该活性可以修饰λDNA使其不被HaeIII切割。同样的体外修饰DNA仍然易被其他限制性内切酶切割。
