Hoffmann P J
J Virol. 1981 Jun;38(3):1005-14. doi: 10.1128/JVI.38.3.1005-1014.1981.
Reaction intermediates formed during the degradation of linear PM2, T5, and lambda DNA by herpes simplex virus (HSV) DNase have been examined by agarose gel electrophoresis. Digestion of T5 DNA by HSV type 2 (HSV-2) DNase in the presence of Mn(2+) (endonuclease only) gave rise to 6 major and 12 minor fragments. Some of the fragments produced correspond to those observed after cleavage of T5 DNA by the single-strand-specific S1 nuclease, indicating that the HSV DNase rapidly cleaves opposite a nick or gap in a duplex DNA molecule. In contrast, HSV DNase did not produce distinct fragments upon digestion of linear PM2 or lambda DNA, which do not contain nicks. In the presence of Mg(2+), when both endonuclease and exonuclease activities of the HSV DNase occur, most of the same distinct fragments from digestion of T5 DNA were observed. However, these fragments were then further degraded preferentially from the ends, presumably by the action of the exonuclease activity. Unit-length lambda DNA, EcoRI restriction fragments of lambda DNA, and linear PM2 DNA were also degraded from the ends by HSV DNase in the same manner. Previous studies have suggested that the HSV exonuclease degrades in the 3' --> 5' direction. If this is correct, and since only 5'-monophosphate nucleosides are produced, then HSV DNase should "activate" DNA for DNA polymerase. However, unlike pancreatic DNase I, neither HSV-1 nor HSV-2 DNase, in the presence of Mg(2+) or Mn(2+), activated calf thymus DNA for HSV DNA polymerase. This suggests that HSV DNase degrades both strands of a linear double-stranded DNA molecule from the same end at about the same rate. That is, HSV DNase is apparently capable of degrading DNA strands in the 3' --> 5' direction as well as in the 5' --> 3' direction, yielding progressively smaller double-stranded molecules with flush ends. Except with minor differences, HSV-1 and HSV-2 DNases act in a similar manner.
通过琼脂糖凝胶电泳对单纯疱疹病毒（HSV）脱氧核糖核酸酶（DNase）降解线性PM2、T5和λDNA过程中形成的反应中间体进行了研究。在存在锰离子（仅内切核酸酶）的情况下，用2型单纯疱疹病毒（HSV - 2）DNase消化T5 DNA产生了6个主要片段和12个次要片段。产生的一些片段与单链特异性S1核酸酶切割T5 DNA后观察到的片段相对应，这表明HSV DNase能迅速在双链DNA分子中的切口或缺口相对处进行切割。相比之下，HSV DNase在消化不含切口的线性PM2或λDNA时并未产生明显的片段。在存在镁离子的情况下，当HSV DNase的内切核酸酶和外切核酸酶活性都发挥作用时，能观察到T5 DNA消化产生的大多数相同的明显片段。然而，这些片段随后会优先从末端进一步降解，推测是外切核酸酶活性作用的结果。单位长度的λDNA、λDNA的EcoRI限制性片段以及线性PM2 DNA也以同样的方式被HSV DNase从末端降解。先前的研究表明HSV外切核酸酶沿3'→5'方向降解。如果这是正确的，并且由于只产生5'-单磷酸核苷，那么HSV DNase应该能为DNA聚合酶“激活”DNA。然而，与胰腺DNase I不同，在存在镁离子或锰离子的情况下，HSV - 1和HSV - 2 DNase都不能为HSV DNA聚合酶激活小牛胸腺DNA。这表明HSV DNase从线性双链DNA分子的同一末端以大致相同的速率降解两条链。也就是说，HSV DNase显然能够沿3'→5'方向以及5'→3'方向降解DNA链，产生末端平齐且逐渐变小的双链分子。除了细微差异外，HSV - 1和HSV - 2 DNase的作用方式相似。
