KANSAS CITY, MO -- Each time a cell divides -- and it takes millions of cell divisions to create a fully grown human body from a single fertilized cell -- its chromosomes have to be accurately divvied up between both daughter cells. Researchers at the Stowers Institute for Medical Research used, ironically enough, the single-celled organism Saccharomyces cerevisiae -- commonly known as baker's yeast -- to gain new insight into the process by which chromosomes are physically segregated during cell division.
In a study published in the Nov. 17, 2011 issue of PLoS Genetics, they demonstrate that a protein known as Mps3 not only ensures that cells have two functional spindle pole bodies, which generate the mitotic spindle apparatus that helps pull the chromosomes apart, but also that both spindle pole bodies are properly anchored in the nuclear membrane.
"When you enter mitosis, you need to have two spindle pole bodies on which you can pull the chromosomes. If you don't, the probability of errors in chromosome segregation increases exponentially," explains Jaspersen, adding that, "even small mistakes can lead to birth defects, genetic instability and cancer."
Normally, cells have only a single spindle pole body, but in preparation for cell division, the spindle pole body has to duplicate itself just as the genome does. "We know a whole lot about how DNA copies itself, but we don't know much about how spindle pole bodies duplicate themselves," says Jaspersen.
Unlike DNA molecules, which serve as templates for the production of identical copies, the spindle pole body is a large protein structure composed of soluble proteins and so-called integral membrane proteins, which are anchored in the nuclear envelope. The duplication process of the lone spindle pole body begins when soluble proteins coalesce on the nuclear envelope followed by their insertion into the lipid bi-layer located next to the original spindle pole body. Insertion p
|Contact: Gina Kirchweger|
Stowers Institute for Medical Research