Localization of cyclin A at the sites of cellular DNA replication

Exp Cell Res. 1993 May;206(1):43-8. doi: 10.1006/excr.1993.1118.


Cyclin A is a nuclear protein which is part of a kinase complex with either p34cdc2 or p33cdk2. Cyclin A is required in higher eukaryotic cells at the G1/S and the G2/M transitions. To examine the relationship between cyclin A and DNA replication, we simultaneously labeled exponentially growing HeLa cells for the distribution of cyclin A and proliferating cell nuclear antigen (PCNA). We have now demonstrated, by means of immunoelectron microscopy, that cyclin A is located at the sites of DNA replication visualized by both BrdU and PCNA labeling. Thus cyclin A may play a significant role in the phosphorylation of proteins at or near the sites of DNA replication.

MeSH terms

  • Bromodeoxyuridine / metabolism
  • Cell Nucleus / chemistry
  • Cell Nucleus / metabolism
  • Cell Nucleus / ultrastructure
  • Cyclins / analysis*
  • Cyclins / physiology
  • DNA / metabolism
  • DNA Replication*
  • HeLa Cells
  • Humans
  • Microscopy, Immunoelectron
  • Nuclear Proteins / analysis
  • Phosphorylation
  • Proliferating Cell Nuclear Antigen


  • Cyclins
  • Nuclear Proteins
  • Proliferating Cell Nuclear Antigen
  • DNA
  • Bromodeoxyuridine