Heterochromatin: silence is golden
Heterochromatin: silence is golden
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DOI：
10.1016/j.cub.2003.11.006
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发表时间：
2003-12-02
期刊：
影响因子：
9.2
通讯作者：
Grewal, SIS
中科院分区：
文献类型：
--
作者：
Elgin, SCR;Grewal, SIS
高等真核生物的大基因组表明需要稳定的包装，特别是因为大多数DNA不编码蛋白质，而且大部分由重复序列组成，包括入侵的反转录转座子的残余，转座子元件等。细胞学研究首先证明，许多重复的DNA是以一种称为异染色质的浓缩形式包装的，并表明这种包装限制了转录。近年来，异染色质的生物化学特性研究取得了显著进展，揭示了异染色质形成和维持的机制。异染色质的一个重要特征是这种包装方式是表观遗传的；即包装状态通常在复制和有丝分裂后维持，与潜在的DNA序列无关。这意味着生化标记和细胞机制可以识别和维持局部标记。真核生物基因组的DNA被包装在核小体中，大约167个碱基对（bp）的DNA被包裹在八个组蛋白（[H3+ H4] 2四聚体和[H2A+ H2B]的两个二聚体）的核心的两个左旋中。组蛋白H1与DNA结合在DNA进入和退出与核心结合的地方。约10 - 50bp的“连接子”dna延伸到下一个组蛋白核心。三分之二的核心组蛋白的羧基端建立了非常稳定的相互作用，产生了
The large genomes of higher eukaryotes suggest a need for stable packaging, particularly as most of the DNA does not code for proteins, and much consists of repetitious sequences, including remnants of invading retrotransposons, transposable elements and the like. Cytological studies first demonstrated that much of the repetitous DNA is packaged in a condensed form referred to as heterochromatin, and indicated that such packaging limits transcription. During the last few years, remarkable progress has been made in identifying the biochemical characteristics of heterochromatin, suggesting mechanisms by which heterochromatin formation is targeted and maintained.Biochemical marks of heterochromatin An important characteristic of heterochromatin is that this mode of packaging is epigenetically inherited; ie the packaging state is generally maintained after replication and mitosis, independent of the underlying DNA sequence. This implies a biochemical mark and a cellular machinery that can recognize and maintain the mark locally. The DNA of eukaryotic genomes is packaged in nucleosomes, with around 167 base pairs (bp) of DNA wrapped in two left-handed turns around a core of eight histones (an [H3+ H4] 2 tetramer and two dimers of [H2A+ H2B]). Histone H1 binds to the DNA where the DNA enters and exits from association with the core.‘Linker’DNA of around 10–50 bp extends to the next histone core. The carboxyterminal two thirds of the core histones establish the very stable interactions that create the