Eick D, Stabel S, Doerfler W
J Virol. 1980 Oct;36(1):41-9. doi: 10.1128/JVI.36.1.41-49.1980.
Spontaneously arising morphological revertants of the adenovirus type 12 (Ad12)-transformed hamster cell line T637 had been previously isolated, and it had been demonstrated that in these revertants varying amounts of the integrated Ad12 genome were eliminated from the host genome. In this report, the patterns of persistence of the viral genome in the revertants were analyzed in detail. In some of the revertant cell lines, F10, TR3, and TR7, all copies of Ad12 DNA integrated in line T637 were lost. In lines TR1, -2, -4 to -6, -8 to -10, and -13 to -16, only the right-hand portion of one Ad12 genome was preserved; it consisted of the intact right segment of Ad12 DNA and was integrated at the same site as in line T637. In revertant lines G12, TR11, and TR12, one Ad12 DNA and varying parts of a second viral DNA molecule persisted in the host genome. These patterns of persistence of Ad12 DNA molecules in different revertants supported a model for a mode of integration of Ad12 DNA in T637 hamster cells in which multiple (20 to 22) copies of the entire Ad12 DNA were serially arranged, separated from each other by stretches of cellular DNA. The occurrence of such revertants demonstrated that foreign DNA sequences could not only be acquired but could also be lost from eucaryotic genomes. There was very little, if any, expression of Ad12-specific DNA sequences in the revertant lines TR7 and TR12. Moreover, Ad12 DNA sequences which were found to be undermethylated in line T637 were completely methylated in the revertant cell lines G12, TR11, TR12, and TR2. These findings were consistent with the absence of T antigen from the revertant lines reported earlier. Hence it was conceivable that the expression of integrated viral DNA sequences was somehow dependent on their positions in the cellular genome. In cell line TR637, the early segments of Ad12 DNA were expressed and undermethylated; conversely, in the revertant lines G12, TR11, TR12, and TR2, the same segments appeared to be expressed to a limited extent and were strongly methylated.
先前已分离出腺病毒12型（Ad12）转化的仓鼠细胞系T637自发产生的形态回复突变体，并且已经证明在这些回复突变体中，整合的Ad12基因组的不同数量片段从宿主基因组中被消除。在本报告中，详细分析了病毒基因组在回复突变体中的存留模式。在一些回复突变细胞系F10、TR3和TR7中，整合到T637细胞系中的所有Ad12 DNA拷贝都丢失了。在TR1、-2、-4至-6、-8至-10以及-13至-16细胞系中，仅保留了一个Ad12基因组的右手部分；它由Ad12 DNA完整的右片段组成，并整合在与T637细胞系相同的位点。在回复突变细胞系G12、TR11和TR12中，一个Ad12 DNA和第二个病毒DNA分子的不同部分保留在宿主基因组中。Ad12 DNA分子在不同回复突变体中的这些存留模式支持了一种Ad12 DNA在T637仓鼠细胞中的整合模式模型，即整个Ad12 DNA的多个（20至22）拷贝串联排列，彼此由一段细胞DNA隔开。这些回复突变体的出现表明，外源DNA序列不仅可以被真核基因组获取，也可以从真核基因组中丢失。在回复突变细胞系TR7和TR12中，几乎没有（如果有的话）Ad12特异性DNA序列的表达。此外，在T637细胞系中发现的未甲基化的Ad12 DNA序列在回复突变细胞系G12、TR11、TR12和TR2中完全甲基化。这些发现与早期报道的回复突变细胞系中不存在T抗原一致。因此，可以想象整合的病毒DNA序列的表达在某种程度上取决于它们在细胞基因组中的位置。在TR637细胞系中，Ad12 DNA的早期片段表达且未甲基化；相反，在回复突变细胞系G12、TR11、TR12和TR2中，相同的片段似乎仅在有限程度上表达且高度甲基化。
