Sadoni Nicolas, Cardoso M Cristina, Stelzer Ernst H K, Leonhardt Heinrich, Zink Daniele
University of Munich (LMU), Department Biology II, Grosshaderner Str. 2, 82152 Planegg-Martinsried, Germany.
J Cell Sci. 2004 Oct 15;117(Pt 22):5353-65. doi: 10.1242/jcs.01412. Epub 2004 Oct 5.
DNA replication occurs in mammalian cells at so-called replication foci occupying defined nuclear sites at specific times during S phase. It is an unresolved problem how this specific spatiotemporal organization of replication foci is determined. Another unresolved question remains as to what extent DNA is redistributed during S phase. To investigate these problems, we visualized the replicating DNA and the replication machinery simultaneously in living HeLa cells. Time-lapse analyses revealed that DNA was not redistributed to other nuclear sites during S phase. Furthermore, the results showed that DNA is organized into stable aggregates equivalent to replication foci. These aggregates, which we call sub-chromosomal foci, stably maintained their replication timing from S phase to S phase. During S-phase progression, the replication machinery sequentially proceeded through spatially adjacent sets of sub-chromosomal foci. These findings imply that the specific nuclear substructure of chromosomes and the order of their stable subunits determine the spatiotemporal organization of DNA replication.
DNA复制在哺乳动物细胞的所谓复制位点发生，这些位点在S期的特定时间占据特定的核位置。复制位点的这种特定时空组织是如何确定的，这是一个尚未解决的问题。另一个未解决的问题是，在S期DNA重新分布的程度如何。为了研究这些问题，我们在活的HeLa细胞中同时观察了正在复制的DNA和复制机制。延时分析表明，在S期DNA不会重新分布到其他核位置。此外，结果表明DNA被组织成与复制位点等效的稳定聚集体。我们将这些聚集体称为亚染色体位点，它们从一个S期到下一个S期稳定地维持其复制时间。在S期进程中，复制机制依次通过空间上相邻的亚染色体位点组。这些发现表明，染色体的特定核亚结构及其稳定亚基的顺序决定了DNA复制的时空组织。
