Stuhlmann H, Jähner D, Jaenisch R
Cell. 1981 Oct;26(2 Pt 2):221-32. doi: 10.1016/0092-8674(81)90305-6.
We studied mechanisms controlling gene expression during animal development using retroviruses as model genes. For this, substrains of mice have been previously derived carrying the Moloney leukemia virus (M-MuLV) in their germ line. Virus activation occurs in some of these substrains at different stages of development, resulting in two classes of viral genomes. The genetically transmitted (endogenous) copy is present in every cell, whereas somatically acquired ("exogenous") copies are carried only in cells that were superinfected. We compared these two classes of M-MuLV genomes using two parameters. DNA sequences of the endogenous M-MuLV genome in all mouse substrains were highly methylated in GCGC, the recognition sequence of the restriction enzyme Hha I, and were not infectious (specific infectivity less than 10(-7) pfu per proviral genome) in a DNA transfection assay. In contrast, the "exogenous" copies were hypomethylated and infectious. These parameters are strongly correlated to genome activity in the animal: only tissues carrying exogenous copies express virus-specific RNA. With the assumption that gene expression of transfected DNA is controlled by mechanisms that are relevant for gene expression in the animal, our results suggest that DNA methylation plays a causative role in gene regulation during development and differentiation.
我们使用逆转录病毒作为模型基因，研究了动物发育过程中控制基因表达的机制。为此，先前已培育出一些小鼠亚系，其生殖系中携带莫洛尼白血病病毒（M-MuLV）。在这些亚系中的一些，病毒激活发生在发育的不同阶段，产生两类病毒基因组。遗传传递的（内源性）拷贝存在于每个细胞中，而体细胞获得的（“外源性”）拷贝仅存在于被超感染的细胞中。我们使用两个参数比较了这两类M-MuLV基因组。在所有小鼠亚系中，内源性M-MuLV基因组的DNA序列在限制性内切酶Hha I的识别序列GCGC中高度甲基化，并且在DNA转染试验中无感染性（每个前病毒基因组的特异性感染性小于10^(-7) pfu）。相比之下，“外源性”拷贝甲基化程度低且具有感染性。这些参数与动物体内的基因组活性密切相关：只有携带外源性拷贝的组织才表达病毒特异性RNA。假设转染DNA的基因表达受与动物基因表达相关的机制控制，我们的结果表明DNA甲基化在发育和分化过程中的基因调控中起因果作用。
