Bogenhagen D F, Wormington W M, Brown D D
Cell. 1982 Feb;28(2):413-21. doi: 10.1016/0092-8674(82)90359-2.
Cloned 5S RNA genes added to Xenopus oocyte nuclear extract assemble into stable active transcription complexes that persist for many rounds of 5S RNA synthesis. This stability of the complex has been demonstrated by its resistance to dilution and to competitor DNA. A stable complex is formed within minutes and lasts for at least 40 rounds of transcription per template over several hours. Stable, transcriptionally inactive complexes can be formed by incubation of cloned 5S RNA genes in an oocyte nuclear extract depleted of a 5S-specific transcription factor and supplemented with histones. The stable, transcriptionally active and inactive states of 5S RNA gene complexes that can be formed in vitro are analogous to the states of the somatic and oocyte 5S RNA genes as they exist in somatic cell chromatin. Oocyte 5S RNa genes remain repressed in chromatin isolated from somatic cells, but can be activated by washing chromatin with high salt. Maintenance of the differentiated state of cell requires that selected genes remain stably active while others are stably repressed for long periods of time. We propose that stable transcription complexes may play an important role in the maintenance of the differentiated state in eucaryotic cells.
添加到非洲爪蟾卵母细胞核提取物中的克隆5S RNA基因组装成稳定的活性转录复合物，该复合物能持续进行多轮5S RNA合成。复合物的这种稳定性已通过其对稀释和竞争DNA的抗性得到证明。稳定的复合物在数分钟内形成，并且在数小时内每个模板至少持续40轮转录。通过在缺乏5S特异性转录因子并补充组蛋白的卵母细胞核提取物中孵育克隆的5S RNA基因，可以形成稳定的、转录无活性的复合物。体外可形成的5S RNA基因复合物的稳定、转录活性和无活性状态类似于它们存在于体细胞染色质中的体细胞和卵母细胞5S RNA基因的状态。卵母细胞5S RNA基因在从体细胞分离的染色质中保持沉默，但可以通过用高盐洗涤染色质来激活。细胞分化状态的维持要求特定基因长时间保持稳定活性，而其他基因则保持稳定抑制。我们提出，稳定的转录复合物可能在真核细胞分化状态的维持中起重要作用。
