Dnmt1 overexpression causes genomic hypermethylation, loss of imprinting, and embryonic lethality
Dnmt1 overexpression causes genomic hypermethylation, loss of imprinting, and embryonic lethality
复制标题
DOI：
10.1128/mcb.22.7.2124-2135.2002
复制
发表时间：
2002-04-01
影响因子：
5.3
通讯作者：
Jaenisch, R
中科院分区：
文献类型：
--
作者：
Biniszkiewicz, D;Gribnau, J;Jaenisch, R
Igf2的双等位基因表达在癌症中常见，因为Igf2作为存活因子发挥作用。在许多肿瘤中，Igf2表达的激活与印记区域的从头甲基化相关。我们比较了Igf2和H19的印迹区域、其他印迹基因、大量基因组DNA和重复的逆转录病毒序列对Dnmt 1过表达的内在亲和力。在低Dnmt1甲基转移酶水平重复逆转录病毒元件被甲基化和沉默。Igf2和H19的非甲基化印迹区域在低Dnmt 1水平下对甲基化具有抗性，但当Dnmt 1从细菌人工染色体转基因中过表达时，其变得完全甲基化。甲基化导致野生型和Dnmt 1敲除细胞中沉默Igf2等位基因的激活，导致双等位基因Igf2表达。与此相反，印记基因Igf2r，Peg3，Snrpn和Grf1是完全耐从头甲基化，即使当Dnmt1过表达。因此，Igf2和H19的印迹区域与其他印迹基因的合子后从头甲基化之间的内在差异可能是经常观察到的从头甲基化和肿瘤细胞和肿瘤中Igf2上调的分子基础。在二倍体或四倍体胚泡中注射Dnmt 1过表达的胚胎干细胞导致胚胎死亡，这类似于Dnmt 1缺乏引起的胚胎死亡。
Biallelic expression of Igf2 is frequently seen in cancers because Igf2 functions as a survival factor. In many tumors the activation of Igf2 expression has been correlated with de novo methylation of the imprinted region. We have compared the intrinsic susceptibilities of the imprinted region of Igf2 and H19, other imprinted genes, bulk genomic DNA, and repetitive retroviral sequences to Dnmt1 overexpression. At low Dnmt1 methyltransferase levels repetitive retroviral elements were methylated and silenced. The nonmethylated imprinted region of Igf2 and H19 was resistant to methylation at low Dnmt1 levels but became fully methylated when Dnmt1 was overexpressed from a bacterial artificial chromosome transgene. Methylation caused the activation of the silent Igf2 allele in wild-type and Dnmt1 knockout cells, leading to biallelic Igf2 expression. In contrast, the imprinted genes Igf2r, Peg3, Snrpn, and Grf1 were completely resistant to de novo methylation, even when Dnmt1 was overexpressed. Therefore, the intrinsic difference between the imprinted region of Igf2 and H19 and of other imprinted genes to postzygotic de novo methylation may be the molecular basis for the frequently observed de novo methylation and upregulation of Igf2 in neoplastic cells and tumors. Injection of Dnmt1-overexpressing embryonic stem cells in diploid or tetraploid blastocysts resulted in lethality of the embryo, which resembled embryonic lethality caused by Dnmt1 deficiency.