Death, division or cancer? Newly discovered checkpoint process holds the line in cel...( Each day a staggering number of cell...)

Each day, a staggering number of cells perform a feat that still amazes researchers with its complexity: they divide to produce perfect replicas of each other. The process is called mitosis, and an inability to control it is one of the hallmarks of cancer.

Little is known about the biochemical processes that control mitosis, but now researchers from Fox Chase Cancer Center and Technion-Israel Institute of Technology in Haifa, Israel, have discovered a novel activity, called the mitotic checkpoint factor 2 (MCF2). This appears to be integral in preventing cells that are unable to equally separate their chromosomes from dividing. The identities of the proteins involved in MCF2 remain to be determined, however, their findings offer insight into a fundamental question of biology, which may also help to increase the efficiency of cancer drugs that disrupt DNA replication, like gemcitabine, or drugs that prevent mitosis, like paclitaxel.

They publish their findings today online in the Early Edition of the Proceedings of the National Academy of Sciences.

"At any given moment, 250 million cells in your body are undergoing mitosis in order to replenish cells that die as a result of normal turnover," says Tim J. Yen, Ph.D., senior member at Fox Chase. "The mitotic checkpoint is a complex series of quality control systems, just like in a factory assembly line, that ensures that each new cell gets their proper share of DNA."

"Cancer cells tend to bypass quality control, such as the mitotic checkpoint, so as to allow them to shuffle their deck of chromosomes to select for traits that promote drug resistance and the ability to divide uncontrollably," says Yen.

Yen, along with visiting researcher Avram Hershko, Ph.D., of Technion, discovered the ability of MCF2 to block mitosis by shutting down an ubiquitin ligase enzyme known as the anaphase-promoting complex/cyclosome (APC/C). Hershko was awarded the 2004 Nobel Prize
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