Yamada Y, Nakada D
J Virol. 1975 Dec;16(6):1483-91. doi: 10.1128/JVI.16.6.1483-1491.1975.
A characteristic phenomenon in the F-factor-mediated inhibition of T7 phage is a virtual absence of T7 late protein synthesis in T7-infected Escherichia coli male cells, in spite of the presence of T7 late mRNA which is translatable in vitro when isolated from the cell. To determine whether the translational defect in T7-infected F+ cells is due to a T7 late mRNA-specific translational block, or to a general decrease of F+ cell translational activity, we compared the activities of cell-free, protein-synthesizing systems prepared from isogenic F- and F+ cells harvested at different times of T7 infection. The cell-free systems from uninfected F- and F+ cells translated T7late mRNA equally as well as MS2 RNA and T7early mRNA. The activity of cell-free systems from T7-infected F+ cells to translate MS2 RAN, T7 early mRNA, and T7 late mRNA decreased concomitantly at a much faster rate than that of T7-infected F- cells. Therefore, the abortive infection of F+ cells by T7 does not result from a T7 late mRNA-specific translational inhibition, although a general reduction of the translational activity appears to be a major factor for the inability of the F+ cells to produce a sufficient amount of T7 late proteins.
F 因子介导的对 T7 噬菌体的抑制作用中的一个特征现象是，在 T7 感染的大肠杆菌雄性细胞中几乎不存在 T7 晚期蛋白质合成，尽管存在 T7 晚期 mRNA，当从细胞中分离出来时，它在体外是可翻译的。为了确定 T7 感染的 F+细胞中的翻译缺陷是由于 T7 晚期 mRNA 特异性翻译阻断，还是由于 F+细胞翻译活性的普遍降低，我们比较了在 T7 感染的不同时间收获的同基因 F-和 F+细胞制备的无细胞蛋白质合成系统的活性。未感染的 F-和 F+细胞的无细胞系统翻译 T7 晚期 mRNA 的效果与翻译 MS2 RNA 和 T7 早期 mRNA 的效果相同。T7 感染的 F+细胞的无细胞系统翻译 MS2 RNA、T7 早期 mRNA 和 T7 晚期 mRNA 的活性下降速度比 T7 感染的 F-细胞快得多。因此，T7 对 F+细胞的流产感染不是由 T7 晚期 mRNA 特异性翻译抑制引起的，尽管翻译活性的普遍降低似乎是 F+细胞无法产生足够量的 T7 晚期蛋白质的主要因素。
