Graessle S, Loidl P, Brosch G
Department of Microbiology, University of Innsbruck, Medical School, Austria.
Cell Mol Life Sci. 2001 May;58(5-6):704-20. doi: 10.1007/pl00000894.
The basic element of chromatin is the nucleosome. Histones H4, H3, H2A and H2B form the core histone octamer by protein-protein interactions of their folded domains. The free, flexible N-terminal extensions of the histones protrude from the nuclesome; they contain conserved lysines undergoing posttranslational acetylation. Histone acetyltransferases (HATs) transfer the acetyl moiety of acetyl-coenzyme A to the epsilon-amino group; this reaction is reverted by histone deacetylases (HDACs). The dynamic equilibrium of the acetylation/deacetylation reaction varies throughout the genome; some regions in chromatin undergo rapid acetylation/deacetylation, whereas others are fixed in a certain acetylation state without significant changes. In general, chromatin regions engaged in transcription display dynamic acetylation, i.e. HATs and HDACs are recruited to these regions. Higher plants and fungi have considerably contributed to the unraveling of the multiplicity of HDACs; in particular, plants possess HDACs that have so far not been identified in animal cells.
染色质的基本元件是核小体。组蛋白H4、H3、H2A和H2B通过其折叠结构域的蛋白质-蛋白质相互作用形成核心组蛋白八聚体。组蛋白自由、灵活的N端延伸从核小体中伸出；它们含有经历翻译后乙酰化的保守赖氨酸。组蛋白乙酰转移酶（HATs）将乙酰辅酶A的乙酰部分转移到ε-氨基上；该反应可被组蛋白脱乙酰酶（HDACs）逆转。乙酰化/去乙酰化反应的动态平衡在整个基因组中各不相同；染色质中的一些区域经历快速的乙酰化/去乙酰化，而其他区域则固定在某种乙酰化状态，没有显著变化。一般来说，参与转录的染色质区域表现出动态乙酰化，即HATs和HDACs被招募到这些区域。高等植物和真菌对揭示HDACs的多样性有很大贡献；特别是，植物拥有迄今为止在动物细胞中尚未发现的HDACs。
