Cell type-specific responses of human cells to inhibition of replication licensing

Oncogene. 2002 Sep 26;21(43):6624-32. doi: 10.1038/sj.onc.1205910.


Replication origins are 'licensed' for a single initiation event by loading Mcm2-7 complexes during late mitosis and G1. Licensing is blocked at other cell cycle stages by the activity of cyclin-dependent kinases and a small protein called geminin. Here, we describe the effects of over-expressing a non-degradable form of geminin in various cell lines. Geminin expression reduced the quantity of Mcm2 bound to chromatin and blocked cell proliferation. U2OS (p53+/Rb+) cells showed an early S phase arrest with high cyclin E and undetectable cyclin A levels, consistent with the activation of an intra-S checkpoint. Saos2 (p53-/Rb-) cells showed an accumulation of cells in late S and G2/M with approximately normal levels of cyclin A, consistent with loss of this intra-S phase checkpoint. Geminin also induced apoptosis in both these cell lines. In contrast, IMR90 primary fibroblasts over-expressing geminin arrested in G1 with reduced cyclin E levels and no detectable apoptosis. A 'licensing checkpoint' may therefore act in primary cells to prevent passage into S phase in the absence of sufficient origin licensing. These results suggest that inhibition of the licensing system may cause cancer-specific cell killing and therefore represent a novel anti-cancer target.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenoviridae / genetics
  • Antineoplastic Agents / pharmacology
  • Cell Cycle
  • Cell Cycle Proteins / physiology*
  • Cell Division
  • DNA Replication* / drug effects
  • DNA-Binding Proteins / physiology
  • Geminin
  • Humans
  • Minichromosome Maintenance Complex Component 2
  • Minichromosome Maintenance Complex Component 7
  • Nuclear Proteins / physiology
  • Tumor Cells, Cultured


  • Antineoplastic Agents
  • CDT1 protein, human
  • Cell Cycle Proteins
  • DNA-Binding Proteins
  • GMNN protein, human
  • Geminin
  • Nuclear Proteins
  • MCM7 protein, human
  • Minichromosome Maintenance Complex Component 2
  • Minichromosome Maintenance Complex Component 7