Genome complexity: cell division (Introduction)

by David Turell , Monday, October 05, 2015, 14:24 (3338 days ago) @ David Turell

A complex mechanical marvel. Not by chance:-http://www.sciencedaily.com/releases/2015/10/151002133158.htm-"In order to segregate chromosomes into the two emerging cells, the spindle itself needs a bipolar structure, and so the microtubules must be sorted to align with the long pole-to-pole axis of the spindle. This job is accomplished by kinesin-5, which can bind to two overlapping microtubules, linking them like a bar in the letter H, and directing them to the appropriate locations.-"For this study, the researchers took a detailed look at the physical forces generated by the motor protein as it helps organize the mitotic spindle.-"To do the sorting, kinesin-5 can link two anti-parallel microtubules, pushing them in opposite directions, so their minus ends move away from the spindle's center and toward the spindle's poles. The force exerted by kinesin-5 in that process hasn't been previously measured.-"By shining a laser light on a microscopic-sized plastic bead attached to a pair of microtubules linked by kinesin-5 molecules, the team tracked their activity and discovered that this force is a function of the microtubule overlap--the longer the overlap, the greater the force. "This is a way by which the cell can tune the amount of force it needs in order to build a nice balanced spindle structure," Forth says.-"Kinesin-5 can also link parallel microtubules, and the researchers found that in this case, it behaves differently. Rather than producing a pushing force, it generates a resisting force that can slow down the microtubules' motion. And here again, that force scales up with the length of overlap between the microtubules.-"'We believe that kinesin-5 has the ability to coordinate the speed of microtubules and keep them from going too fast or too slow," says Forth, likening the protein to a gear box in a car. "It helps coordinate and govern the speed and location of the microtubules in the spindle." As many kinesin-5 molecules work together directing microtubules, they become the governing force of the spindle formation."-Comment: In cell division the daughter cells must have exactly the same chromosomes, otherwise chaos. Error correction mechanisms are known to help if necessary.