Reconstitution of chromatin in vitro.
Reconstitution of chromatin in vitro.
复制标题
体外染色质重建。
作者：
K. Ura;Y. Kaneda
现在普遍认为DNA甲基化是哺乳动物基因组印记的原因(1)。最近的实验证据为DNA甲基化抑制基因表达提供了一种很好的机制。这一证据表明，识别特定甲基化的CPGS的蛋白质可能有助于形成不活跃的染色质(2-5)。核小体是染色质的基本单位，由包裹在组蛋白八聚体(H_2A、H_2B、H_3和H_4各两个分子)周围的146个碱基的DNA核心和相邻核小体之间的一段连接DNA组成。第五个组蛋白的结合，称为连接物组蛋白或H1，促进一串串的核小体包装成30 nm的染色质纤维(6)。将DNA包装到核小体和染色质纤维中，极大地限制了DNA用于转录等核过程。
It is now generally believed that DNA methylation is responsible for genomic imprinting in mammals (1). Recent experimental evidence has provided an elegant mechanism for repression of gene expression by DNA methylation. This evidence suggests that proteins that recognize specifically methylated CpGs may contribute to the formation of inactive chromatin (2-5). Nucleosomes are the basic unit of chromatin, consisting of a core of 146 bp of DNA wrapped around a histone octamer (two molecules of each of H2A, H2B, H3, and H4) and a stretch of linker DNA between adjacent nucleosomes. The binding of a fifth histone, known as a linker histone or H1, promotes the packaging of strings of nucleosomes into a 30 nm chromatin fiber (6). Packaging of DNA into nucleosomes and the chromatin fiber greatly restricts the availability of the DNA for nuclear processes such as transcription.