The Geminin and Idas coiled coils preferentially form a heterodimer that inhibits Geminin function in DNA replication licensing.
Geminin is an important regulator of proliferation and differentiation in metazoans, which predominantly inhibits the DNA replication licensing factor Cdt1, preventing genome over-replication. We show that Geminin preferentially forms stable coiled-coil heterodimers with its homologue, Idas. In contrast to Idas-Geminin heterodimers, Idas homodimers are thermodynamically unstable and are unlikely to exist as a stable macromolecule under physiological conditions. The crystal structure of the homology regions of Idas in complex with Geminin showed a tight head-to-head heterodimeric coiled-coil. This Idas-Geminin heterodimer binds Cdt1 less strongly than Geminin-Geminin, still with high affinity (∼30 nm), but with notably different thermodynamic properties. Consistently, in Xenopus egg extracts, Idas-Geminin is less active in licensing inhibition compared with a Geminin-Geminin homodimer. In human cultured cells, ectopic expression of Idas leads to limited over-replication, which is counteracted by Geminin co-expression. The properties of the Idas-Geminin complex suggest it as the functional form of Idas and provide a possible mechanism to modulate Geminin activity.
From the Division of Biochemistry, The Netherlands Cancer Institute, 1066 CX Amsterdam, The Netherlands.
Christophe
C
Caillat
Dafni-Eleftheria
DE
Pefani
Peter J
PJ
Gillespie
Stavros
S
Taraviras
J Julian
JJ
Blow
Zoi
Z
Lygerou
Anastassis
A
Perrakis
D000818:Animals; D018797:Cell Cycle Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004261:DNA Replication / Q000502:physiology*; D064248:Geminin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D055503:Protein Multimerization / Q000502:physiology*; D020836:Protein Structure, Quaternary; D013329:Structure-Activity Relationship; D014157:Transcription Factors; D014982:Xenopus laevis
C467199:CDT1 protein, human; D018797:Cell Cycle Proteins; C577995:GMNN protein, human; D064248:Geminin; C560898:MCIDAS protein, human; D009687:Nuclear Proteins; D014157:Transcription Factors
Coiled Coil; DNA Replication; Isothermal Titration Calorimetry; Protein Stability; X-ray Crystallography; X-ray Scattering; Xenopus