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首页> 外文期刊>Molecular and Cellular Biology >Role of Methylation in the Induced and Spontaneous Expression of the Avian Endogenous Virus ev-1: DNA Structure and Gene Products
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Role of Methylation in the Induced and Spontaneous Expression of the Avian Endogenous Virus ev-1: DNA Structure and Gene Products

机译：甲基化在禽内源性病毒ev-1的诱导和自发表达中的作用：DNA结构和基因产物

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The endogenous avian provirus ev-1 is widespread in white leghorn chickens. Although it has no major structural defects, ev-1 has not been associated with any phenotype and is ordinarily expressed at a very low level. In this report, we describe a chicken embryo (Number 1836) cell culture containing both ev-1 and ev-6 which spontaneously expressed the ev-1 provirus. This culture released a high level of noninfectious virions containing a full complement of virion structural (gag) proteins but devoid of reverse transcriptase activity or antigen. These virions contained 70S RNA closely related to the genome of Rous-associated virus type 0, but identifiable as the ev-1 genome by oligonucleotide mapping. A fraction of the RNA molecules in the 70S complex were unusual in that they were polyadenylated 100 to 200 nucleotides downstream of the usual polyadenylation site. Eight sibling embryo cultures did not share this unusual phenotype with 1836, indicating that it was not inherited. However, an identical phenotype was inducible in the sibling cultures by treatment with 5-azacytidine, an inhibitor of DNA methylation, and the induced expression was stable for more than 10 generations. Analysis of chromatin structure and DNA methylation of the ev-1 provirus in 1836 cells revealed the presence (in a fraction of the proviruses) of both DNase I hypersensitive sites in the long terminal repeats and in gag and a pattern of cleavage sites for methyl-sensitive restriction endonuclease not found in a nonexpressing sibling. These results lend strong support to the role of DNA methylation in the control of gene expression. Additionally, they explain the lack of phenotype associated with ev-1 as due to a combination of its low expression and defectiveness in pol and env.
机译：内源性禽原病毒 ev -1广泛存在于白色来亨鸡中。尽管没有主要的结构缺陷，但 ev -1并未与任何表型相关，通常以非常低的水平表达。在此报告中，我们描述了同时包含 ev -1和 ev -6的鸡胚（第1836号）细胞培养物，它们自发地表达 ev -1前病毒。这种培养物释放出高水平的非感染性病毒粒子，其中包含完整的病毒粒子结构（ gag ）蛋白补体，但没有逆转录酶活性或抗原。这些病毒体包含与0型劳斯相关病毒基因组密切相关的70S RNA，但通过寡核苷酸作图可鉴定为 ev -1基因组。 70S复合物中的一部分RNA分子是不寻常的，因为它们在通常的聚腺苷酸化位点下游被100-200个核苷酸聚腺苷酸化。 1836年，八个兄弟姐妹胚胎培养物没有共享这种不同寻常的表型，表明它不是遗传的。但是，通过用5-甲基氮杂胞苷（一种DNA甲基化的抑制剂）处理，可以在同胞培养物中诱导出相同的表型，并且诱导的表达稳定了十代以上。分析1836细胞中 ev -1原病毒的染色质结构和DNA甲基化，发现长末端重复序列和中都存在DNase I超敏位点（在原病毒的一部分中） gag 和在非表达同胞中未发现的甲基敏感限制性核酸内切酶的切割位点模式。这些结果为DNA甲基化在基因表达控制中的作用提供了有力的支持。此外，他们解释了与 ev -1相关的表型的缺乏，这是由于其低表达和 pol 和 env中的缺陷所造成的。

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