Doerfler W, Orend G, Schubbert R, Fechteler K, Heller H, Wilgenbus P, Schröer J
Institut für Genetik, Universität zu Köln, Germany.
Gene. 1995 May 19;157(1-2):241-5. doi: 10.1016/0378-1119(95)00080-p.
We have studied the integration of adenovirus type 12 (Ad12) DNA in transformed and hamster tumor cells over many years. Upon infection of hamster cells with Ad12, viral DNA has been found in association with hamster chromosomes, possibly in part integrated into the host genome. Ad12 DNA integration is not sequence specific. Transcriptionally active sites of the host genome show a preponderance for foreign DNA insertion. We are pursuing the mechanism of Ad12 DNA integrative recombination in a cell-free system prepared from hamster cell nuclear extracts. In a number of Ad12-transformed hamster cell lines or in cell lines carrying foreign DNA, we have located the inserted Ad12 DNA copies on hamster chromosomes by fluorescent in situ hybridization (FISH). Among the consequences of Ad12 DNA integration, we have studied the de novo methylation of the integrated foreign (Ad12) DNA and increases in DNA methylation in several cellular genes and DNA segments in Ad12-transformed and hamster tumor cells. Several lines of evidence argue for the notion that parameters in addition to nucleotide sequence, in particular site of integration and/or the chromatin configuration of the integrated DNA, are important in generating de novo methylation patterns. The de novo methylation of integrated foreign DNA can be interpreted as an old cellular defense mechanism against the activity of foreign genes in an established genome. Pursuing this concept, we have asked for the most likely portal of entry of foreign DNA, supposedly the gastrointestinal tract in most animals. This hypothesis has been tested by feeding mice linearized or circular, double-stranded bacteriophage M13mp18 DNA.(ABSTRACT TRUNCATED AT 250 WORDS)
多年来，我们一直在研究12型腺病毒（Ad12）DNA在转化的仓鼠肿瘤细胞中的整合情况。用Ad12感染仓鼠细胞后，发现病毒DNA与仓鼠染色体相关联，可能部分整合到宿主基因组中。Ad12 DNA整合不具有序列特异性。宿主基因组的转录活性位点显示出对外源DNA插入的偏好。我们正在从仓鼠细胞核提取物制备的无细胞系统中研究Ad12 DNA整合重组的机制。在一些Ad12转化的仓鼠细胞系或携带外源DNA的细胞系中，我们通过荧光原位杂交（FISH）在仓鼠染色体上定位了插入的Ad12 DNA拷贝。在Ad12 DNA整合的后果中，我们研究了整合的外源（Ad12）DNA的从头甲基化以及Ad12转化的和仓鼠肿瘤细胞中几个细胞基因和DNA片段中DNA甲基化的增加。几条证据支持这样一种观点，即除核苷酸序列外，特别是整合位点和/或整合DNA的染色质构型等参数在产生从头甲基化模式中很重要。整合的外源DNA的从头甲基化可以解释为一种古老的细胞防御机制，以对抗已建立基因组中外源基因的活性。基于这一概念，我们探讨了外源DNA最可能的进入途径，推测在大多数动物中是胃肠道。通过给小鼠喂食线性化或环状的双链噬菌体M13mp18 DNA对这一假设进行了测试。（摘要截短于250字）
