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Quaternary structure of the human Cdt1-Geminin complex regulates DNA replication licensing
V De Marco1, P J Gillespie, A Li
1Department of Biochemistry, Netherlands Cancer Institute, Plesmanlaan 121, 1066CX Amsterdam, The Netherlands.
Summary
Organisms prevent DNA rereplication using origin licensing. Geminin inhibits Cdt1, a key licensing factor, by forming distinct complexes, acting as a molecular switch to control DNA replication.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Organisms must prevent DNA rereplication within a single cell cycle.
- Eukaryotes utilize origin licensing, controlling prereplicative complex (pre-RC) assembly.
- Cdt1 is a critical regulator of pre-RC assembly, and Geminin inhibits Cdt1 in higher eukaryotes to prevent rereplication.
Purpose of the Study:
- To elucidate the mechanism by which Geminin inhibits DNA licensing.
- To investigate the structural and functional states of the Cdt1:Geminin complex.
Main Methods:
- X-ray crystallography to determine complex structures.
- Small-angle X-ray scattering (SAXS) for structural analysis.
- Functional studies in Xenopus and mammalian cell systems.
Main Results:
- The Cdt1:Geminin complex exists in two forms: a permissive heterotrimer and an inhibitory heterohexamer.
- Specific Cdt1 residues, inaccessible in the heterohexamer, are crucial for DNA licensing.
- The transition between these two complex forms acts as a molecular switch.
Conclusions:
- Geminin inhibits DNA licensing by inducing a conformational change in Cdt1, shifting it to an inactive state.
- The structural plasticity of the Cdt1:Geminin complex is key to regulating DNA replication.
- This provides a molecular basis for preventing DNA rereplication in eukaryotes.
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