Stable chromosomal units determine the spatial and temporal organization of DNA replication.
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.
Sadoni
Nicolas
N
University of Munich (LMU), Department Biology II, Grosshaderner Str. 2, 82152 Planegg-Martinsried, Germany.
Cardoso
M Cristina
MC
Stelzer
Ernst H K
EH
Leonhardt
Heinrich
H
Zink
Daniele
D
D000818:Animals; D002453:Cell Cycle; D002875:Chromosomes / Q000648:ultrastructure*; D004247:DNA / Q000737:chemistry; D004261:DNA Replication; D004330:Drosophila; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D008957:Models, Genetic; D015530:Nuclear Matrix / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D016196:S Phase; D013997:Time Factors
D049452:Green Fluorescent Proteins; D004247:DNA