Lavi S, Rozenblatt S, Singer M F, Winocour E
J Virol. 1973 Sep;12(3):492-500. doi: 10.1128/JVI.12.3.492-500.1973.
Three plaque isolates of SV40 strain 777 and 1 plaque isolate of strain 776 were grown to high-titer stocks and serially passaged, undiluted, in monkey BS-C-1 cells. In each case, the serial passaging procedure resulted in the accumulation of closed-circular SV40 DNA molecules containing covalently linked sequences homologous to reiterated host cell DNA (called substituted virus DNA). The relative yields, at a given passage level, of SV40 DNA with measurable homology to host DNA varied in different sets of serial passages, including passages of the same virus clone. More reproducible yields of substituted viral DNA progeny were obtained when the serial passaging procedure was initiated from earlier passages rather than from the original plaque-purified stock. Fractionation of closed-circular SV40 DNA molecules on alkaline sucrose gadients indicated that the majority of substituted virus DNA molecules are not plaque producers and are slightly smaller in size than plaque-forming DNA molecules which display no detectable homology to host DNA. Evidence that substituted SV40 DNA molecules replicate during serial undiluted passage was obtained from experiments which demonstrated (i) the presence of host sequences in replicative forms of the viral DNA and (ii) the incorporation of (3)H-thymidine into host sequences isolated from the mature substituted virus DNA molecule.
将SV40毒株777的三个噬菌斑分离株和毒株776的一个噬菌斑分离株培养至高滴度储备液，并在猴BS-C-1细胞中进行连续传代（不稀释）。在每种情况下，连续传代过程导致积累了闭环SV40 DNA分子，这些分子含有与重复的宿主细胞DNA同源的共价连接序列（称为取代病毒DNA）。在给定传代水平下，与宿主DNA具有可测量同源性的SV40 DNA的相对产量在不同的连续传代组中有所不同，包括同一病毒克隆的传代。当从较早传代而非原始噬菌斑纯化储备液开始连续传代过程时，可获得更可重复的取代病毒DNA子代产量。在碱性蔗糖梯度上对闭环SV40 DNA分子进行分级分离表明，大多数取代病毒DNA分子不是噬菌斑产生者，其大小略小于与宿主DNA无可检测同源性的噬菌斑形成DNA分子。从实验中获得了取代的SV40 DNA分子在连续不稀释传代过程中复制的证据，这些实验表明：（i）病毒DNA复制形式中存在宿主序列；（ii）将³H-胸腺嘧啶掺入从成熟取代病毒DNA分子中分离的宿主序列中。
