Fujimura F K, Linney E
Proc Natl Acad Sci U S A. 1982 Mar;79(5):1479-83. doi: 10.1073/pnas.79.5.1479.
Mouse embryonal carcinoma cells are refractory to infection by wild-type polyoma virus, the infection process apparently being blocked at a stage after adsorption and penetration but before early protein synthesis. Polyoma virus mutants capable of productive infection of mouse embryonal carcinoma cells have been isolated and these mutants all have DNA sequence alterations in a noncoding region near the origin of replication of the viral genome. PyF101 and PyF441 are two mutants selected for their ability to infect the embryonal carcinoma cell line F9. Here we show that these PyF mutants do not rescue replication of wild-type polyoma during a mixed infection of F9 cells. The mutant and wild-type DNAs were distinguished on the basis of restriction fragments obtained by digestion with Msp I or BstNI, and no wild-type DNA was detected in F9 cells coinfected with wild-type polyoma and with either PyF101 or PyF441. The mutant viruses do not appear to inhibit wild-type replication during a mixed infection because both mutant and wild-type DNAs can replicate efficiently in coinfected 3T6 cells which are permissive for both mutant and wild-type viruses. A double mutant having the PyF101 mutation and the ts-25E temperature-sensitive mutation in polyoma large tumor antigen was constructed and found to be temperature-sensitive for replication in F9 cells. This double mutant, designated PyFts-1, can be rescued in F9 cells at the restrictive temperature by coinfection with PyF441. These results suggest that the PyF mutations affect two processes in F9 cells, one involving expression of polyoma early genes and a second involving viral DNA replication.
小鼠胚胎癌细胞对野生型多瘤病毒的感染具有抗性，感染过程显然在吸附和穿透后的某个阶段受阻，但在早期蛋白质合成之前。已分离出能够在小鼠胚胎癌细胞中进行有效感染的多瘤病毒突变体，这些突变体在病毒基因组复制起点附近的非编码区域均有DNA序列改变。PyF101和PyF441是因其感染胚胎癌细胞系F9的能力而被挑选出的两个突变体。在此我们表明，在F9细胞的混合感染中，这些PyF突变体无法拯救野生型多瘤病毒的复制。基于用Msp I或BstNI消化获得的限制性片段区分突变型和野生型DNA，在与野生型多瘤病毒以及PyF101或PyF441共感染的F9细胞中未检测到野生型DNA。在混合感染期间，突变病毒似乎不会抑制野生型复制，因为突变型和野生型DNA在对突变型和野生型病毒均敏感的共感染3T6细胞中都能有效复制。构建了一个在多瘤大肿瘤抗原中具有PyF101突变和ts - 25E温度敏感突变的双突变体，发现其在F9细胞中的复制对温度敏感。这个名为PyFts - 1的双突变体在限制温度下通过与PyF441共感染可在F9细胞中得到拯救。这些结果表明，PyF突变影响F9细胞中的两个过程，一个涉及多瘤病毒早期基因的表达，另一个涉及病毒DNA复制。
