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Planta

, Volume 215, Issue 2, pp 195–204 | Cite as

Dynamics of replication foci and nuclear matrix during S phase in Allium cepa L. cells

  • Rafael Samaniego
  • Consuelo de la Torre
  • Susana Moreno Díaz de la Espina
Original Article

Abstract.

The sequential organisation of replication foci during S phase in onion (Allium cepa) and their relationship to the nuclear matrix were investigated. To discern their structural features and temporal firing sequence, immunodetection of 5-bromo-2′-deoxyuridine (BrdU) was carried out after in vivo feeding in synchronised cells released from a 14-h-long hydroxyurea block. Replication foci consisted of small replication granules, called replisomes, which clustered together. Analysis of synchronous binucleate cells that maintained in their two nuclei the specular symmetry of distribution of sister chromosomes in anaphase, showed that replication starts in small replication foci at the telomeric pole (pattern I), though the telomeres themselves formed large foci that were late-replicating. The rDNA replication foci (pattern II) also become replicated in early S phase. Replication of large foci, including the heterochromatin (IV), occurred in late S phase and finished at the centromeric nuclear pole (pattern V). Labelling of proliferating cell nuclear antigen (PCNA) in nuclear matrices, prepared from S-phase nuclei after extensive DNase digestion, demonstrated that replication foci were always stably anchored to the nuclear matrix. Thus, association with the nucleoskeleton is not exclusively mediated by the replicating or nascent DNA. The overlapping of patterns I, II and III in the nuclear matrix, in contrast to the results of BrdU localisation in nuclei, suggests that PCNA becomes associated with the nuclear matrix before the replication foci are operative, and remains bound during replication.

Allium cepa Bromodeoxyuridine immunofluorescence Cell cycle DNA replication foci Nuclear matrix Proliferating cell nuclear antigen 

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Copyright information

© Springer-Verlag 2002

Authors and Affiliations

  • Rafael Samaniego
    • 1
  • Consuelo de la Torre
    • 2
  • Susana Moreno Díaz de la Espina
    • 1
  1. 1.Nuclear Matrix Laboratory, Centro de Investigaciones Biológicas, CSIC, Velázquez 114, 28006 Madrid, Spain
  2. 2.Cell Proliferation Laboratory, Centro de Investigaciones Biológicas, CSIC, Velázquez 114, 28006 Madrid, Spain

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