Donze David, Kamakaka Rohinton T
Department of Biological Sciences, Louisiana State University, USA.
Bioessays. 2002 Apr;24(4):344-9. doi: 10.1002/bies.10072.
Eukaryotic DNA is assembled into nucleosomes, which are further packaged into higher order chromatin structures containing many non-histone chromosomal proteins. The details of this packaging have profound effects on gene expression and other cellular processes involving the genetic material. Heterochromatic domains of the genome are usually transcriptionally repressed, while euchromatic regions are transcriptionally competent. Current models of gene activation postulate the existence of boundary elements that either prevent inappropriate activation of genes by distal enhancers (enhancer blockers), or sequences that block the propagation of heterochromatin into euchromatic regions (barriers). While numerous boundary sequences have been identified, little is known with regard to the molecular mechanisms used to punctuate the genome. This review will focus on recent data that provide insight into the mode of action of barrier elements.
真核生物的DNA组装成核小体，核小体进一步包装成包含许多非组蛋白染色体蛋白的高级染色质结构。这种包装的细节对基因表达和涉及遗传物质的其他细胞过程具有深远影响。基因组的异染色质结构域通常转录受抑制，而常染色质区域具有转录活性。当前的基因激活模型假定存在边界元件，这些边界元件要么阻止远端增强子对基因的不适当激活（增强子阻断剂），要么阻止异染色质向常染色质区域的传播（屏障）。虽然已经鉴定出许多边界序列，但对于用于划分基因组的分子机制知之甚少。本综述将聚焦于提供对屏障元件作用模式深入了解的最新数据。
