Brandeis M, Ariel M, Cedar H
Department of Cellular Biochemistry, Hebrew University, Jerusalem, Israel.
Bioessays. 1993 Nov;15(11):709-13. doi: 10.1002/bies.950151103.
DNA methylation plays a role in the repression of gene expression in animal cells. In the mouse preimplantation embryo, most genes are unmethylated but a wave of de novo methylation prior to gastrulation generates a bimodal pattern characterized by unmethylated CpG island-containing housekeeping genes and fully modified tissue-specific genes. Demethylation of individual genes then takes place during cell type specific differentiation, and this demodification may be a required step in the process of transcriptional activation. DNA modification is also involved in the maintenance of gene repression on the inactive X chromosome in female somatic cells and the marking of parental alleles at genomically imprinted gene loci.
DNA甲基化在动物细胞基因表达的抑制中发挥作用。在小鼠植入前胚胎中，大多数基因是未甲基化的，但在原肠胚形成之前的一波从头甲基化产生了一种双峰模式，其特征是含有未甲基化CpG岛的管家基因和完全修饰的组织特异性基因。然后，在细胞类型特异性分化过程中，个别基因会发生去甲基化，这种去修饰可能是转录激活过程中的一个必要步骤。DNA修饰还参与维持雌性体细胞中失活X染色体上的基因抑制，以及在基因组印记基因座对亲本等位基因进行标记。
