Portal de Periódicos da CAPES

Quaternary structure of the human Cdt1-Geminin complex regulates DNA replication licensing

2009; National Academy of Sciences; Volume: 106; Issue: 47 Linguagem: Inglês

10.1073/pnas.0905281106

1091-6490

Valeria De Marco, Peter J. Gillespie, A. Li, Nikolaos Karantzelis, Evangelos Christodoulou, Rob Klompmaker, Suzan van Gerwen, Alexander Fish, Maxim V. Petoukhov, Maria S. Iliou, Zoi Lygerou, René H. Medema, J. Julian Blow, Dmitri I. Svergun, Stavros Taraviras, Anastassis Perrakis,

DNA and Nucleic Acid Chemistry

All organisms need to ensure that no DNA segments are rereplicated in a single cell cycle. Eukaryotes achieve this through a process called origin licensing, which involves tight spatiotemporal control of the assembly of prereplicative complexes (pre-RCs) onto chromatin. Cdt1 is a key component and crucial regulator of pre-RC assembly. In higher eukaryotes, timely inhibition of Cdt1 by Geminin is essential to prevent DNA rereplication. Here, we address the mechanism of DNA licensing inhibition by Geminin, by combining X-ray crystallography, small-angle X-ray scattering, and functional studies in Xenopus and mammalian cells. Our findings show that the Cdt1:Geminin complex can exist in two distinct forms, a “permissive” heterotrimer and an “inhibitory” heterohexamer. Specific Cdt1 residues, buried in the heterohexamer, are important for licensing. We postulate that the transition between the heterotrimer and the heterohexamer represents a molecular switch between licensing-competent and licensing-defective states.