ScienceDaily (Nov. 27, 2010) — Scientists have discovered an amazingly simple way that cells stabilize their machinery for forcing apart chromosomes.
Their findings are reported Nov. 25 inNature.
When a cell gets ready to split into new cells, this stable set-up permits its genetic material to be separated and distributed accurately. Otherwise, problem cells — like cancer cells — arise.
The human body contains more than a trillion cells, and every single cell needs to have the exact same set of chromosomes. Mistakes in moving chromosomes during cell division can lead to babies being born with genetic conditions like Down syndrome, where cells have an extra copy of chromosome 21.
“A striking hallmark of cancer cells,” said one of the senior authors of the study, Sue Biggins, an investigator in the Basic Science Division, Fred Hutchinson Cancer Research Center in Seattle, “is that they contain the wrong number of chromosomes, so it is essential that that we understand how chromosome separation is controlled. This knowledge would potentially lead to ways to correct defects before they occur, or allow us to try to target cells with the wrong number of chromosomes to prevent them from dividing again.”
The machine inside cells that moves the chromosomes is the kinetochore.
These appear on the chromosomes and attach to dynamic filaments during cell division. Kinetochores drive chromosome movement by keeping a grip on the filaments, which are constantly remodeling. The growth and shortening of the filaments tugs on the kinetochores and chromosomes until they separate.
“The kinetochore is one of the largest cellular machines but had never been isolated before,” Biggins said, “Our labs isolated these machines for the first time. This allowed us to analyze their behavior outside of the cell and find out how they control movement.”
“We demonstrated that attachments between kinetochores and microtubule filaments become more stable when they are placed under tension,” noted Dr. Charles “Chip” Asbury, a University of Washington (UW) associate professor of physiology and biophysics. Originally trained in mechanical engineering, Asbury studies molecular motors in cells. He is also a senior author on the Nov. 25 Nature paper.
Asbury likened the stabilizing tension on the filament to a Chinese finger trap toy — the harder you try to pull away, the stronger your knuckles are gripped.