BLACKSBURG, Va., March 3, 2014— Researchers at the Virginia Bioinformatics Institute at Virginia Tech have discovered that cells respond to a molecular traffic light surprisingly slow, which enables chromosomes to split safely and create genetically identical daughter cells. Their work is published in the Feb. 27 issue of Current Biology.
In our bodies cells divide every day. They undergo a series of events, the cell cycle, during which they duplicate the genetic information, which is encoded on the chromosomes, and distribute it to the two newly arising daughter cells.
While unraveling the mechanism of cellular division, scientists found that an important signaling network acts as a molecular traffic light or checkpoint. It holds the cell cycle until each chromosome is properly in place. Only once it switches to 'go' the chromosomes separate and the final steps of cell division take place. This ensures that cells retain their identity and the appropriate number of chromosomes. Like in real life, a failure of this molecular traffic light can be catastrophic. A misfunction could result in cancer or Down syndrome.
Importantly, however, once changed to ‘go’ and initiating the separation of the chromosomes, the traffic light should not change back, as it would prevent the cell from dividing properly.
Scientists previously proposed that the traffic light becomes completely switched off, but Silke Hauf, a biology fellow at the Virginia Bioinformatics Institute, and Julia Kamenz, a visiting biology fellow from the Friedrich Miescher Laboratory of the Max Planck Society, show that even if it remains active, the 'stop' signal does not prevent the cell from progressing as the signal is received too slowly.
(Left to right) Silke Hauf, Julia Kamenz, and Katharina Sewart of the Hauf Lab demonstrate that if you are caught in the crosswalk when the red stop hand image displays, your only choice is to keep walking.
“It’s like crossing a big street,” says lead author Julia Kamenz. “You must first wait until the light changes from red to green to begin walking. But now, if the light changes back to red while you are in the middle of the street, you better ignore the lights and keep walking or you’ll never make it across.”
Yet, being slow in responding to the molecular traffic light creates a considerable risk for cells. If the initial 'stop' signal is not recognized fast enough, fatal errors in chromosome segregation can occur. Nevertheless, there seem to be some benefit of slowness, as it appears to be a general feature of the checkpoint: While Kamenz and Hauf carried out their work in yeast, other researchers found that checkpoint signaling is also surprisingly slow in human cells. Hauf and her team suggest that the slow speed of the signal is the result of a trade-off between being reasonably fast to detect errors early during cell division but being slow enough to not encounter problems at the very moment when chromosomes split.
Written by Emily Kale.
A university-level Research Institute of Virginia Tech, the Virginia Bioinformatics Institute was established in 2000 with an emphasis on informatics of complex interacting systems scaling the microbiome to the entire globe. It helps solve challenges posed to human health, security, and sustainability. Headquartered at the Blacksburg campus, the institute occupies 154,600 square feet in research facilities, including state-of-the-art core laboratory and high-performance computing facilities, as well as research offices in the Virginia Tech Research Center in Arlington, Va.
March 03, 2014