Cell cycle control, phosphorylation, chromatin
Laboratory of phosphorylation and cell cycle control
Institut Génétique Moléculaire 1919 route de Mende
1919 Route de Mende
Montpellier Cedex 05
General/Lab Fax: (+33) (-0)4 67 61 36 94
Fisher, Daniel L.
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 ass embly 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. Upstream of Cdks are checkpoint systems which determine the critical choice all cells face: to divide or not to divide, or even to permanently stop dividing (senescence). These checkpoints integrate internal information (the type of cell, and its history) and information from the environment (hormones, nutrients, cell-cell contacts, and physical or chemical stress), to control activation or inhibition of Cdk complexes. How these controls work in the context of the complexity of the organism is far from clear. We are using different primary cells and cell lines to study the biochemistry of cell cycle regulators in circumstances which mimic physiological or pathological stimulation or arrest of proliferation, to understand the molecular mechanisms of these controls.
Daniel Fisher undertook a PhD in the lab of Sir Paul Nurse (Nobel prize 2001) from 1991-1995, working on roles of G1 cyclins in initiation of DNA replication (Hayles, Fisher et al., 1994, Cell; Fisher and Nurse, 1996, EMBO J). As a postdoctoral fellow with Marcel Dorée in Montpellier, he worked on kinase pathways leading to Cdk1 activation in Xenopus (Fisher et al., 1999a, Development; Fisher et al, 1999b, Development; Fisher et al., 2000, EMBO J.). He then studied the influence of DNA replication on gene expression during development in Xenopus and pluripotent somatic cells (Fisher and Méchali, 2003, EMBO J.). In 2005 Daniel Fisher moved to the IGMM in Montpellier to set up the lab "Phosphorylation control of the vertebrate cell cycle", using mainly the Xenopus system. The lab now includes 8 members: 2 postdocs, 3 PhD students, 3 permanent scientists, from the UK (Daniel Fisher), France, Croatia and Poland. The IGMM and Montpellier The Institut de Génétique Moléculaire de Montpellier (Institute of Molecular Genetics) , directed by Jean-Marie Blanchard, is a modern, international institute located on the CNRS/University campus in Montpellier, in the south of France. The themes cover the Cell cycle, Apoptosis, Chromatin function and epigenetics, RNA structure and function, Metabolism and Immunology/ Virology. 18 research groups and 180 personnel are represented. Models include Xenopus, transgenic mice, yeast, drosophila and somatic cultured cells. For more information please see our web pages (www.igmm.cnrs.fr). Montpellier is a dynamic city of 250,000 located close to the Mediterranean sea (15 km). The weather, surrounding countryside, cultural and leisure opportunities, food, wine and young population provide a quality of life with few rivals. It has high speed rail connections to Paris (3 hours) and an airport with daily flights to European destinations.