Rice S A, Klessig D F, Williams J
Virology. 1987 Feb;156(2):366-76. doi: 10.1016/0042-6822(87)90416-8.
The early region 2A gene (E2A) of adenovirus types 2 and 5 encodes a 72-kDa DNA binding protein (DBP) which contains two physical domains comprising approximately the amino-terminal one-third and carboxyl-terminal two-thirds of the protein, respectively. Previous work has shown that some Ad5 mutants containing temperature-sensitive (ts) mutations in the carboxyl-terminal domain of DBP, such as Ad5ts125, show a 3- to 8-fold enhanced ability to transform rat cells. We have examined the transformation characteristics of a series of Ad5 E2A deletion mutants, Ad5dl801-5, which encode either no functional DBP or encode truncated, defective DBPs. The E2A deletion mutants transformed rat embryo cells at frequencies similar to wild-type (wt) Ad5. These results suggest that the high transformation phenotype of carboxyl-terminal E2A mutants like Ad5ts125 is not due to the simple inactivation of DBP function, but rather results from an activity possessed by an altered DBP. This hypothesis is supported by the fact that the transformation phenotype of Adsts125 and similar mutants is dominant over the wild-type phenotype. A number of additional Ad2 and Ad5 E2A mutants were examined with respect to their ability to transform primary rat embryo cells. It was found that a carboxyl-terminal E2A mutant, Ad2+ND1ts23, also showed the enhanced transformation phenotype. In contrast, several amino-terminal E2A host-range (hr) mutants, originally isolated on the basis of their ability to replicate in monkey cells, transformed rat embryo cells at a frequency similar to wild-type virus. Ad2ts400, and E2A mutant with alterations in both DBP domains, showed a wild-type frequency of transformation, while two similar mutants, Ad5ts125 X 405 and Ad5ts125 X 404, showed an enhanced frequency. Last, it was found that coinfection of primary rat embryo cells with the hr mutants plus Ad5ts125 or Ad2+ND1ts23 resulted in a wild-type frequency of transformation, demonstrating that the hr mutants are dominant to the ts mutants with regard to transformation phenotype. Thus, DBP can both positively and negatively affect viral transformation in this system.
腺病毒2型和5型的早期区域2A基因（E2A）编码一种72 kDa的DNA结合蛋白（DBP），该蛋白包含两个物理结构域，分别约占该蛋白氨基末端的三分之一和羧基末端的三分之二。先前的研究表明，一些在DBP羧基末端结构域含有温度敏感（ts）突变的Ad5突变体，如Ad5ts125，在转化大鼠细胞方面的能力增强了3至8倍。我们研究了一系列Ad5 E2A缺失突变体Ad5dl801 - 5的转化特性，这些突变体要么不编码功能性DBP，要么编码截短的、有缺陷的DBP。E2A缺失突变体转化大鼠胚胎细胞的频率与野生型（wt）Ad5相似。这些结果表明，像Ad5ts125这样的羧基末端E2A突变体的高转化表型并非由于DBP功能的简单失活，而是由改变后的DBP所具有的一种活性导致的。Adsts125和类似突变体的转化表型相对于野生型表型具有显性这一事实支持了这一假设。我们还研究了许多其他Ad2和Ad5 E2A突变体转化原代大鼠胚胎细胞的能力。结果发现，一个羧基末端E2A突变体Ad2 + ND1ts23也表现出增强的转化表型。相比之下，几个最初基于在猴细胞中复制能力分离得到的氨基末端E2A宿主范围（hr）突变体，转化大鼠胚胎细胞的频率与野生型病毒相似。Ad2ts400是一个在两个DBP结构域都有改变的E2A突变体，表现出野生型的转化频率，而两个类似的突变体Ad5ts125 X 405和Ad5ts125 X 404则表现出增强的频率。最后，发现用hr突变体与Ad5ts125或Ad2 + ND1ts23共同感染原代大鼠胚胎细胞会导致野生型的转化频率，这表明在转化表型方面，hr突变体相对于ts突变体具有显性。因此，在这个系统中，DBP既能对病毒转化产生正向影响，也能产生负向影响。
