Gluzman Y, Kuff E L, Winocour E
J Virol. 1977 Nov;24(2):534-40. doi: 10.1128/JVI.24.2.534-540.1977.
Passage of the simian virus 40 (SV40) temperature-sensitive (ts) mutant tsD202 at the permissive temperature in each of three permissive lines of SV40-transformed monkey CV1 cells resulted in the emergence of temperature-insensitive virus, which plated like wild-type SV40 at the restrictive temperature on normal CV1 cells. In independent experiments, the amount of temperature-insensitive virus that appeared after passage on transformed cells was from 10(3)- to 10(6)-fold greater than the amount of ts-revertant virus that appeared after an equal number of passages in nontransformed CV1 cells. The virus rescued by passage on transformed cells bred true upon sequential plaque purification, plated on normal CV1 cells with single-hit kinetics at the restrictive temperature, and displayed no selective growth advantage on transformed cells compared to non-transformed cells. Hence, the reversion of the ts phenotype is neither due to complementation effects nor to the selection of preexisting revertants, which grow better on transformed cells. In the accompanying article (T. Vogel et al., J. Virol. 24:541-550, 1977), we present biochemical evidence that the rescue of tsD202 mediated by passage on transformed cells is due to recombination with the resident SV40 genome. Parallel experiments in which tsA, tsB, and tsC SV40 mutants were passaged in each of the three permissive lines of SV40-transformed monkey cells resulted in either only borderline levels of rescue (tsA mutants) or no detectable rescue (tsB and tsC mutants). Evidence is presented that the resident SV40 genome of the transformed monkey lines is itself a late ts mutant, and we suggest that this accounts for the lack of detectable rescue of the tsB and tsC mutants. We furthermore suggest that the borderline level of rescue observed with two tsA mutants is related to a previous finding (Y. Gluzman et al., J. Virol. 22:256-266, 1977) which indicated that the resident SV40 genome of the permissive transformed monkey cells is defective in the function required for initiation of viral DNA synthesis.
猿猴病毒40（SV40）温度敏感（ts）突变体tsD202在三个SV40转化的猴CV1细胞允许系中的每个系里，于允许温度下传代，导致出现了温度不敏感病毒，该病毒在限制温度下能像野生型SV40一样在正常CV1细胞上形成噬斑。在独立实验中，在转化细胞上传代后出现的温度不敏感病毒量比在未转化的CV1细胞中进行相同传代次数后出现的ts回复病毒量高10³至10⁶倍。通过在转化细胞上传代拯救的病毒在连续空斑纯化后能稳定遗传，在限制温度下以单次打击动力学在正常CV1细胞上形成噬斑，并且与未转化细胞相比，在转化细胞上没有显示出选择性生长优势。因此，ts表型的回复既不是由于互补效应，也不是由于对预先存在的回复突变体的选择，这些回复突变体在转化细胞上生长得更好。在随附的文章（T. Vogel等人，《病毒学杂志》24:541 - 550，1977年）中，我们提供了生化证据，表明通过在转化细胞上传代介导的tsD202的拯救是由于与常驻SV40基因组的重组。平行实验中，tsA、tsB和tsC SV40突变体在三个SV40转化的猴细胞允许系中的每个系里传代，结果要么只有临界水平的拯救（tsA突变体），要么没有可检测到的拯救（tsB和tsC突变体）。有证据表明，转化猴细胞系中的常驻SV40基因组本身就是一个晚期ts突变体，我们认为这解释了tsB和tsC突变体缺乏可检测到的拯救的原因。我们还认为，观察到的两个tsA突变体的临界拯救水平与之前的一项发现（Y. Gluzman等人，《病毒学杂志》22:256 - 266，1977年）有关，该发现表明允许性转化猴细胞的常驻SV40基因组在病毒DNA合成起始所需的功能上存在缺陷。
