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Cdt1 downregulation by proteolysis and geminin inhibition prevents DNA re-replication in Xenopus

Anatoliy Li1, J Julian Blow

  • 1Wellcome Trust Biocentre, University of Dundee, Dundee, UK.

The EMBO Journal
|December 24, 2004
PubMed

Insights

DNA replication licensing is tightly controlled by regulating Cdt1 levels through proteolysis and geminin inhibition. Disrupting these mechanisms in Xenopus extracts causes re-replication, limited by checkpoint kinases.

Area of Science:

  • Molecular Biology
  • Cell Cycle Regulation
  • DNA Replication

Background:

  • DNA replication origins must be licensed once per cell cycle to prevent re-replication.
  • Mcm2-7 complex assembly onto origins in late mitosis/G1 licenses them.
  • Origin Recognition Complex, Cdc6, and Cdt1 are essential for licensing.

Purpose of the Study:

  • To investigate the regulation of DNA replication licensing in Xenopus egg extracts.
  • To elucidate the mechanisms preventing re-replication during the cell cycle.

Main Methods:

  • Analysis of Cdt1 regulation in Xenopus egg extracts.
  • Investigating the roles of proteolysis, anaphase-promoting complex (APC/C), and geminin.
  • Observing the effects of abrogating Cdt1 regulatory mechanisms on DNA replication.

Main Results:

  • Cdt1 is downregulated late in the cell cycle via proteolysis (partly APC/C-dependent) and geminin inhibition.
  • Simultaneous abrogation of both Cdt1 regulatory mechanisms leads to uncontrolled re-licensing and re-replication.
  • Checkpoint kinases are activated by re-replication, limiting its extent.

Conclusions:

  • Cdt1 regulation is the key mechanism preventing DNA re-replication in Xenopus.
  • A comprehensive model for replication licensing and control is proposed.
  • Explains the basis for the discovery of replication licensing factors.

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