Three-dimensional model of the retroviral intasome and chemical structures of some of the clinical HIV-1 integrase inhibitors studied in the lab

Peter Cherepanov  : Factors involved in initiation of eukaryotic DNA replication

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Eukaryotic replisome assembly and initiation of the DNA synthesis at individual origins require actions of many proteins and critically depend on activities of S-phase cyclin-dependent kinases (S-CDKs) and Cdc7-Dbf4. Both types of heterodimeric kinases are regulated by their respective activating subunits (cyclins and Dbf4), which oscillate during the cell cycle.

The most characterised role of Cdc7-Dbf4 is phosphorylation of the MCM2-7 complex, required to trigger its DNA helicase activity. Due to its essential role in DNA replication, Cdc7-Dbf4 has been put forward as a target for the development of anti-cancer drugs.

We use x-ray crystallography and complementary approaches to gain structural insights in the initiation of DNA replication. Recently we determined the first crystal of Cdc7-Dbf4 kinase, which elucidated the basis for binding to and activation of Cdc7 by Dbf4 and provided a framework for design of more potent and specific Cdc7 inhibitors.

We are now focusing on the mechanisms of regulation of Cdc7 activity and other structural aspects of initiation of eukaryotic DNA replication.

Crystal structure

Figure 1: (A) Crystal structure of the Cdc7-Dbf4 heterodimer. Cdc7 is colored in green (canonical part of the N-lobe structure), purple (canonical C-lobe structures) and yellow (structures unique to Cdc7) and Dbf4 in orange. (B) Views on the Cdc7 active site engaged with inhibitors PHA767491 (top) or XL413 (bottom). Cdc7 surface is colored according to conservation, with least conserved atoms are shown in red and those most conserved in gray. This figure is adapted from Hughes et al., Nat Struct Mol Biol, 2012, 19:1101–7.