Daniel L. Fisher
An intense research effort in diverse cell models has identified Cyclin dependent kinases (Cdks) as cell-cycle regulators whose fundamental importance is conserved throughout evolution. Cdks act as molecular switches, necessary to trigger transitions in the cell cycle. Indeed, Cdk activation is the primary step that commits a cell to DNA replication and passage through the cell cycle. Recent yeast studies have identified two important substrates whose phosphorylation by Cdks is required for initiation of DNA replication in vivo, yet others are clearly lacking. And in metazoans, no such proteins have been identified. Furthermore, in metazoans, multiple Cdk-cyclin complexes are apparently required for metazoan DNA replication, operating at successive steps of DNA replication. Their respective targets are currently unknown, and why and how multiple Cdk-complexes regulate DNA replication is also not known. Cdks probably have at least two important roles : promoting assembly of active replication initiation complexes, and facilitating a chromatin state permissive for DNA replication. We are using the physiological system of Xenopus egg extracts to study the role of individual Cdk-cyclin complexes in pre-replication complex formation and activation in metazoans. Xenopus egg extracts undergo regulated DNA replication in vitro. Our goal is to describe essential Cdk targets and how their phosphorylation triggers DNA replication, and understand the specificity and redundance of Cdk regulation of DNA replication. To achieve this we are applying a "systems biology" approach of functional proteomics. We are also using a novel chemical-genetic approach to precisely inhibit individual Cdk-cyclin complexes. We have designed and synthesized mutant Xenopus Cdk-cyclin complexes which have wild-type kinase activity but which are resistant to a specific chemical inhibitor. This allows us to test the physiology of such pharmacological Cdk inhibitors, designed as cancer drugs. These two aspects of the project should allow a better understanding of the effects of manipulating the cell cycle in cancer.
Lab MembershipsFisher Lab (Principal Investigator/Director)
Laboratory of phosphorylation and cell cycle control
1919 Route de Mende
Montpellier Cedex 05
(+33) (-0)4 67 04 02 31
Phone: (+33) (-0)4 67 61 36 94