Research interests:

Our lab is interested in genome maintenance mechanisms in large part because genomic instability is thought to be a contributing factor to many diseases including cancer. To ensure genomic integrity, eukaryotic cells are equipped with dedicated sensor response mechanisms that are called cell cycle checkpoints. The checkpoints ensure the high-fidelity transmission of genetic information mainly by controlling DNA replication and cell cycle progression. Our research will focus on DNA replication checkpoint control that is essential when DNA replication is impeded. Impeded replication forks are among the most serious causes for DNA damage and as such pose a grave threat to cell survival and genomic integrity. The investigations utilize mammalian cells and the fission yeast Schizosaccharomyces pombe. Fission yeast has proven to be an exceptional model system for studying genome maintenance mechanisms, most of which appear to be highly conserved in human.

DNA Replication and Cell Cycle Checkpoint Control

Genetic instability is a major factor in the development of many diseases, most notably cancer. Many agents that cause genetic instability do so by interfering with DNA replication. This is when the DNA replication checkpoint control steps in to delay mitosis and control DNA replication, repair and recombination. This surveillance system ensures the high-fidelity transmission of genetic information. A failure in this checkpoint pathway can lead to genetic instability and contribute to cancer development, but at the same time, checkpoints probably play a major role in the survival of cancer cells when they are treated with DNA damaging agents. In fact, inhibition of checkpoint proteins in tumor cells may be an efficient strategy to induce cell death specifically in cancer cells. Therefore, checkpoint proteins are thought to be potentially useful targets of anti-cancer agents.

The DNA replication checkpoint stabilizes replication forks that have stalled at DNA adducts and other lesions that block DNA polymerases. In the absence of the DNA replication checkpoint, stalled forks are thought to collapse, creating double strand break that threatens genome stability and cell viability. Therefore, discovering how cells cope with replication fork arrest is essential for understanding the mechanisms of genome maintenance. We recently found that Swi1 and Swi3 proteins form a Replication
Fork Protection Complex (FPC) that is required for stabilization of replication forks and for effective activation of replication checkpoint kinase Chk2/Cds1 in fission yeast. The Swi1-Swi3 complex is evolutionally conserved and homologous to the Tof1-Csm3 complex in Saccharomyces cerevisiae and the Timeless-Tipin complex in humans.

Since replication fork collapse during DNA replication is one of the most serious threats to cause genetic instability, proteins involved in replication fork stabilization should be one of major targets of anti-cancer drugs. Therefore it is essential to find the network of proteins involved in replication fork stabilization. To pursue this aim, first, we will employ fission yeast Schizosaccharomyces pombe as a model organism. We will isolate FPC interacting proteins by biochemical and genetic strategies. These strategies include protein purification, screening of synthetic lethal mutations and two-hybrid screening. These investigations will lead us to identify the protein network involved in replication fork stabilization. Then, we will expand our studies to mammalian cultured cells to investigate how down-regulation of human FPC impacts genomic instability and contributes to cancer development. In addition, we will also characterize human homologs of FPC interacting factors to confirm their importance in genome maintenance mechanisms.

The investigation revolves around replication forks. Maintenance of replication forks during S-phase is crucial for cell survival and is required for efficient transduction of checkpoint signaling and other genome maintenance mechanims. The investigation of the protein network involved in stabilization of replication forks will provide novel and important insights into genome maintenance mechanism in humans, since they directly have an impact on cancer biology.

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