A Dartmouth research team has determined the structure of a protein vital to cell division, publishing its results in the Jan. 9 issue of Cell, a leading journal in the field.
Jared Cochran, a post-doctoral fellow in chemistry at the College, led the project in the laboratory of chemistry professor F. Jon Kull, Cochran said in an e-mail. Kull is a member of the Class of 1988.
During meiosis -- the process by which a cell divides to form sex cells -- each of the four new cells, following two rounds of division, must receive one set of the parent cell's chromosomes. When the chromosomes do not separate correctly, the cells receive either too little or too much genetic material, which may cause developmental defects.
In the common fruit fly, the protein NOD is crucial for the proper alignment of chromosomes during cell division. This protein is one of a class of motor proteins called kinesins that carries genetic material along microtubules, which are essentially cellular roadways, during division. The Dartmouth group was able to determine the protein's structure using x-rays, according to the published paper.
"As research moves forward, we are beginning to understand the features that these motors share and the features that are unique for each family [of motor proteins]," Cochran said.
While the NOD protein appears only in fruit flies, the team's research may have applications in studies of similar processes in human cells, according to a press release about the discovery.
Research on the protein began in January 2007, and the structural model was fully developed by the end of that year, Cochran said in the e-mail. In addition to determining the protein's chemical structure, the team conducted further tests to determine how the protein functions.
Before this study, the NOD protein was already known to aid in the movement of chromosomes during cell division. During meiosis and mitosis, another form of cell division, the copied chromosomes must line up in the middle of the cell. The protein's involvement was unclear, since NOD cannot actively move along microtubules.
The research group determined that the protein binds to the beginning of a growing microtubule chain, which pushes the protein -- and chromosomes bound to it -- to the center of the cell, where they are properly positioned for division.
"Before this study, it had been shown that kinesin motors either walked along their microtubule tracks or functioned to break microtubules apart," Kull said in the press release. "This work describes a novel mode for kinesin function, in which NOD does not walk, but rather alternates between grabbing on to and letting go of the end of the growing filament, thereby tracking the end as it grows. The diversity of function of these proteins is remarkable."
Cochran believes that more research about the interactions between proteins and microtubules will give scientists a better understanding of the mechanisms by which cells divide.
"This detailed analysis paves the way for understanding how several kinesin motors may interact with microtubules during cell division, both mitosis and meiosis," Cochran said.
Natasha Mulko '07, now studying dentistry at Creighton University, contributed to the research as an undergraduate at Dartmouth and co-authored the paper, Cochran said.
Kull was unavailable for comment by press time. Mulko did not return requests for comment.
