Doerfler W, Hohlweg U, Müller K, Remus R, Heller H, Hertz J
Institute of Genetics, University of Cologne, Köln, Germany.
Ann N Y Acad Sci. 2001 Sep;945:276-88. doi: 10.1111/j.1749-6632.2001.tb03896.x.
We have been interested in the consequences of foreign DNA insertion into established mammalian genomes and have initially studied this problem in adenovirus type 12 (Ad12)-transformed cells or in Ad12-induced hamster tumors. Since integrates are frequently methylated de novo, it appears that they might be modified by an ancient defense mechanism against foreign DNA. In cells transgenic for the DNA of Ad12 or for the DNA of bacteriophage lambda, changes in cellular methylation and transcription patterns have been observed. Thus, the insertion of foreign DNA can have important functional consequences that are not limited to the site of foreign DNA insertion. These findings appear to be relevant also for tumor biology and for the interpretation of data derived from experiments with transgenic organisms. For most animals, the main portal of entry for foreign DNA is the gastrointestinal tract. Large amounts of foreign DNA are regularly ingested with the supply of nutrients. Starting in 1987/1988, we have been investigating the fate of orally administered foreign DNA in mice. Naked DNA of bacteriophage M13 and the cloned gene for the green fluorescent protein (GFP) of Aequorea victoria have been used as test molecules. Moreover, the plant-specific gene for the ribulose-1,5-bisphosphate carboxylase (rubisco) has been followed in mice after feeding soybean leaves. At least transiently, food-ingested DNA can be traced to different organs and, after transplacental transfer, to fetuses and newborns. There is no evidence for germ line transmission or for the expression of orally administered GFP DNA.
我们一直对将外源DNA插入已建立的哺乳动物基因组的后果感兴趣，并最初在12型腺病毒（Ad12）转化的细胞或Ad12诱导的仓鼠肿瘤中研究了这个问题。由于整合体经常从头甲基化，似乎它们可能被一种古老的抵御外源DNA的防御机制所修饰。在转染了Ad12 DNA或噬菌体λ DNA的细胞中，已经观察到细胞甲基化和转录模式的变化。因此，外源DNA的插入可以产生重要的功能后果，这些后果并不局限于外源DNA插入的位点。这些发现似乎也与肿瘤生物学以及对转基因生物实验数据的解释相关。对于大多数动物来说，外源DNA进入的主要途径是胃肠道。随着营养物质的供应，大量的外源DNA会被定期摄入。从1987/1988年开始，我们一直在研究口服给予小鼠的外源DNA的命运。噬菌体M13的裸DNA和维多利亚水母绿色荧光蛋白（GFP）的克隆基因已被用作测试分子。此外，在给小鼠喂食大豆叶后，追踪了核酮糖-1,5-二磷酸羧化酶（rubisco）的植物特异性基因。至少在短时间内，摄入食物中的DNA可以追踪到不同的器官，并且在经胎盘转移后，可以追踪到胎儿和新生儿。没有证据表明存在种系传递或口服给予的GFP DNA会表达。
