PMID: 24064211

Authors:

Caillat C, Pefani ED, Gillespie PJ, Taraviras S, Blow JJ, Lygerou Z, Perrakis A

Title:

The Geminin and Idas coiled coils preferentially form a heterodimer that inhibits Geminin function in DNA replication licensing.

Journal:

J Biol Chem. 2013 Oct 2.

Abstract:

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 (~30nM), but with notably different thermodynamic properties. Consistently, in Xenopus egg extracts, Idas:Geminin is less active in licensing inhibition compared to 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.