非洲爪蟾卵提取物：一种用于染色质复制的模型系统。
Xenopus egg extracts: a model system for chromatin replication.
作者信息
Almouzni G, Méchali M
机构信息
Institut Jacques Monod, Paris, France.
出版信息
Biochim Biophys Acta. 1988 Dec 20;951(2-3):443-50. doi: 10.1016/0167-4781(88)90118-2.
A cell-free system derived from Xenopus eggs enables in vitro reproduction of the steps occurring during eukaryotic DNA replication. With a circular single-stranded DNA template, extracts obtained from high-speed centrifugation perform complementary DNA strand synthesis coupled to chromatin assembly. Nucleosomes are formed on the newly replicated DNA and the overall reaction mimics the events occurring during chromosomal replication on the lagging strand at the replication fork. ATP is necessary at all steps examined individually, including RNA priming, elongation of DNA strands and chromatin assembly. Although not required for nucleosome formation, ATP is involved in the correct spacing of nucleosomes and the stability of the assembled chromatin. Replication of double-stranded DNA was observed only with extracts obtained from low-speed centrifugation using demembraned sperm nuclei as substrate. Nuclei are reconstituted around the DNA and then undergo a series of events characteristic of a cell cycle. In contrast, neither DNA elongation or chromatin assembly require formation of the nucleus, and both are independent of the cell cycle.
源自非洲爪蟾卵的无细胞体系能够在体外重现真核生物DNA复制过程中发生的各个步骤。利用环状单链DNA模板，高速离心获得的提取物可进行与染色质组装偶联的互补DNA链合成。在新复制的DNA上形成核小体，整个反应模拟了复制叉处滞后链上染色体复制过程中发生的事件。在单独检测的所有步骤中，包括RNA引发、DNA链延伸和染色质组装，ATP都是必需的。虽然核小体形成不需要ATP，但ATP参与核小体的正确间距和组装染色质的稳定性。仅在使用去膜精子核作为底物的低速离心获得的提取物中观察到双链DNA的复制。细胞核围绕DNA重建，然后经历一系列细胞周期特征性的事件。相比之下，DNA延伸和染色质组装都不需要细胞核的形成，且两者均独立于细胞周期。
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