Kettmann R, Meunier-Rotival M, Cortadas J, Cuny G, Ghysdael J, Mammerickx M, Burny A, Bernardi G
Proc Natl Acad Sci U S A. 1979 Oct;76(10):4822-6. doi: 10.1073/pnas.76.10.4822.
DNA preparations from circulating leukocytes, lymph node tumors, and spleens of three bovine leukemia virus-infected cattle were fractionated by Cs2SO4/3,6-bis(acetatomercurimethyl)dioxane density gradient centrifugation. Bovine leukemia virus proviral sequences were found in large GC-rich fragments having a buoyant density in CsCl close to 1.708 g/cm3. Provirus integration, therefore, does not take place at random locations in the host genome, but in a specific class of DNA segments. Hybridization of cDNA synthesized on viral RNA to EcoRI and Xba I restriction fragments of the DNA from infected cells showed that: (i) only one copy of proviral DNA is integrated per haploid genome; (ii) different restriction patterns were found in the proviral DNAs present in the genomes of different animals, providing evidence for the existence of several strains or mutants; and (iii) different integration sites for the proviral DNA were found in the genome of different animals and of different infected cells in the same animal. The latter finding strongly suggests a polyclonal origin of bovine leukemia virus-infected cells.
采用硫酸铯/3,6 - 双（乙酰汞甲基）二氧六环密度梯度离心法对3头感染牛白血病病毒的牛的循环白细胞、淋巴结肿瘤和脾脏中的DNA制剂进行分级分离。在富含鸟嘌呤和胞嘧啶（GC）的大片段中发现了牛白血病病毒前病毒序列，这些片段在氯化铯中的浮力密度接近1.708克/立方厘米。因此，前病毒整合并非随机发生在宿主基因组中，而是发生在特定类别的DNA片段中。以病毒RNA合成的cDNA与感染细胞DNA的EcoRI和Xba I限制性片段杂交显示：（i）每个单倍体基因组中仅整合有一份前病毒DNA拷贝；（ii）在不同动物基因组中存在的前病毒DNA中发现了不同的限制性图谱，这为存在几种毒株或突变体提供了证据；（iii）在不同动物以及同一动物的不同感染细胞的基因组中发现了前病毒DNA的不同整合位点。后一发现强烈提示牛白血病病毒感染细胞起源于多克隆。
