To study this at the molecular level, Maresca and colleagues designed experiments to trick the cellular machinery into overexpressing the molecular engine that produces PEF. Surprisingly, this caused a dramatic increase in a type of bad kinetochore-microtubule interaction called syntelic attachments. They also fluorescently tag chromosomes, microtubules, kinetochores and the molecular engine kinesin with different colors to visualize interactions in real time using a special microscope at UMass Amherst able to image single molecules. Quantifying the amount of fluorescence of the force-producing molecular engine, they were able to assess the relative strength of the PEF in cells.
Maresca says, "We see the detection pathway preventing the molecular glue from dissolving until every chromosome is correctly aligned. The delay gives the cell time to correct errors. We propose that these bad syntelic attachments are normally very short-lived because they are not under proper tension. However, when we experimentally elevate PEF, tension is introduced at attachments that do not typically come under tension, essentially tricking the cell into thinking these chromosomes are properly aligned."
Plotting the percent of syntelic attachments versus the amount of PEF, Maresca and colleagues observed an error rate that plateaus at 80 to 90 percent, mirroring and supporting earlier work by others in different cell types. "In cells with elevated PEFs, the correction pathway is overridden, the detection mechanism is silenced and the result is disastrous because it leads to severe aneuploidy. This research has taught us about how an important molecular engine generates the PEF and how this force affects the accuracy of cell division."
|Contact: Janet Lathrop|
University of Massachusetts at Amherst