Imhof A, Becker P B
Department of Molecular Biology, University of Münich, Schillerstr. 44 80336 Münich, Germany.
Mol Biotechnol. 2001 Jan;17(1):1-13. doi: 10.1385/MB:17:1:01.
A multicellular organism is made up of a variety of different cell types and tissues. This organization is accomplished by a well-concerted action of different regulatory molecules, which--in a very hierarchical manner--influence the expression of certain cell-specific genes. Many of those regulators are transcription factors, which directly influence the expression of the controlled gene by binding to a specific DNA sequence within its promoter or enhancer region. This binding then leads to an enhancement or a decrease in the rate of transcription of that particular gene and eventually regulates the production of the corresponding polypeptide. One major obstacle to the binding of these transcription factors is the fact that DNA is not readily accessible in the eukaryotic nucleus. It is associated with a class of very basic proteins called histones. This complex of histones and DNA is called chromatin.
多细胞生物由多种不同的细胞类型和组织构成。这种组织构建是通过不同调控分子的协同作用实现的，这些调控分子以一种非常层级化的方式影响某些细胞特异性基因的表达。其中许多调控因子是转录因子，它们通过与受控基因启动子或增强子区域内的特定DNA序列结合，直接影响该基因的表达。这种结合随后导致该特定基因转录速率的提高或降低，并最终调节相应多肽的产生。这些转录因子结合的一个主要障碍是，在真核细胞核中DNA不易接近。它与一类称为组蛋白的非常碱性的蛋白质相关联。这种组蛋白与DNA的复合物称为染色质。
