Cooper G M, Okenquist S
J Virol. 1978 Oct;28(1):45-52. doi: 10.1128/JVI.28.1.45-52.1978.
The mechanism of transfection by Rous sarcoma virus DNA was investigated by assaying DNA-mediated transformation under conditions which restricted secondary virus infection. Chicken embryo fibroblasts which were genetically resistant to virus infection as a result of the absence of receptors for virus penetration were also resistant to transformation by integrated or unintegrated Rous sarcoma virus DNA. In addition, DNA of replication-defective Bryan hightiter Rous sarcoma virus was noninfectious, and transformation by DNA of a temperature-sensitive DNA polymerase mutant was temperature sensitive. These results indicated that secondary virus infection was necessary for transformation by Rous sarcoma virus DNA. Since transformation was assayed by colony formation in soft agar, as well as by focus formation, the requirement for secondary virus infection was not an artifact of potential difficulty in detection of foci formed by division of single transformed cells. Therefore, it appeared that donor DNA did not stably transform recipient cells by direct integration. Instead, the results were consistent with the hypothesis that transfection of chicken embryo fibroblasts by Rous sarcoma virus DNA proceeded by transcription of donor DNA, formation of extracellular progeny virus, and secondary virus infection of sensitive cells.
通过在限制二次病毒感染的条件下检测DNA介导的转化，研究了劳氏肉瘤病毒DNA的转染机制。由于缺乏病毒穿透受体而对病毒感染具有遗传抗性的鸡胚成纤维细胞，对整合或未整合的劳氏肉瘤病毒DNA的转化也具有抗性。此外，复制缺陷型布赖恩高滴度劳氏肉瘤病毒的DNA无感染性，温度敏感型DNA聚合酶突变体的DNA介导的转化具有温度敏感性。这些结果表明，二次病毒感染是劳氏肉瘤病毒DNA转化所必需的。由于转化是通过软琼脂中的集落形成以及灶形成来检测的，因此对二次病毒感染的需求不是检测由单个转化细胞分裂形成的灶时潜在困难所造成的假象。因此，似乎供体DNA不是通过直接整合来稳定转化受体细胞的。相反，这些结果与以下假设一致：劳氏肉瘤病毒DNA对鸡胚成纤维细胞的转染是通过供体DNA的转录、细胞外子代病毒的形成以及敏感细胞的二次病毒感染来进行的。
