Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Molecule Tracking Reveals Mechanism of Chromosome Separation in Dividing Cells

09.03.2009
Researchers are looking at a control hub on chromosomes that forms during cell division. They are learning how it attaches and maintains its grip to the cellular fiber that lengthen and shorten to separate chromosomes.

University of Washington (UW) researchers are helping to write the operating manual for the nano-scale machine that separates chromosomes before cell division. The apparatus is called a spindle because it looks like a tiny wool-spinner with thin strands of microtubules or spindle fibers sticking out. The lengthening and shortening of microtubules is thought to help push and pull apart chromosome pairs.

Understanding how this machine accurately and evenly divides genetic material is essential to learning why its parts sometimes fail. Certain cancers or birth defects, like Down syndrome or Trisomy 18, result from an uneven distribution of chromosomes.

In a study published March 6 in the journal Cell, a team led by UW scientists reports on the workings of a key component of this machine. Named a kinetochore, it is a site on each chromosome that mechanically couples to spindle fibers.

"Kineochores are also regulatory hubs," the researchers noted. "They control chromosome movements through the lengthening and shortening of the attached microtubules. They sense and correct errors in attachment. They emit a "wait" signal until the microtubules properly attach." Careful control over microtubules, they added, is vital for accurate splitting of the chromosomes.

The lead researchers on the study were Andrew F. Powers and Andrew D. Franck from the UW Department of Physiology and Biophysics and Daniel R. Gestaut, from the UW Department of Biochemistry. The senior authors of the study were Charles "Chip" Asbury, assistant professor, and Linda Wordeman, associate professor, both of physiology and biophysics and both members of the UW Center for Cell Dynamics; and Trisha Davis, professor of biochemistry, and director of the Yeast Resource Center.

Asbury is known for research on molecular machines and motors, Wordeman for work on chromosome movement, and Davis for studies of spindle poles. All are part of the Seattle Mitosis Club led by Sue Biggins at the Fred Hutchinson Cancer Research Center.

To understand how the kinetochore functions, the scientists sought to uncover the basis for its most fundamental behavior: attaching microtubules. The most puzzling aspect of this attachment, according to the researchers, is that the kinetochore has to be strong yet dynamic. It has to keep a grip on the microtubule filaments even as they add and remove their subunits.

"This ability," the researchers said, "allows the kinetochore to harness microtubule shortening and lengthening to drive the movement of chromosomes."

The same coupling behavior is found in living things from yeast cells to humans, indicating that it was conserved during evolution as a good way of getting the job done.

The question is how this mechanism works. Previous studies implicated a large, multiprotein complex, Ndc80, as a direct contact point between kinetochores and microtubules. However, researchers had only a static view of the complex. The UW researchers used special techniques to manipulate and track the activity of the complex in a laboratory set-up.

The researchers were able to show that the Ndc80 complex was indeed capable of forming dynamic, load-bearing attachments to the tips of the microtubules, probably by forming an array of individually weak microtubule binding elements that rapidly bind and unbind, but with a total energy large enough to hold on. The mechanism will produce a molecular friction that resists translocation of the microtubule through the attachment site. Other scientists have dubbed the mechanism a "slip clutch."

This kind of coupler, the researchers added, is able to remain continuously attached to the microtubule tip during both its assembly and disassembly phases. The coupler also can harness the energy released during disassembly to produce mechanical force. Coupling may depend on positively charged areas on the complex that interact with negatively charged hooks on the microtubules by electrostatic force.

Based on their findings, the scientists propose arrays of Ndc80 complexes supply the combination of plasticity and strength that allows kinetechores to hold on loosely but not let go of the tips of the microtubules.

This work was supported by grants from the National Institutes of Health and the National Institute of General Medical Sciences, a Searle Scholar Award, and a Packard Fellowship for Science and Engineering.

Leila Gray | Newswise Science News
Further information:
http://www.washington.edu

More articles from Life Sciences:

nachricht Scientists spin artificial silk from whey protein
24.01.2017 | Deutsches Elektronen-Synchrotron DESY

nachricht Choreographing the microRNA-target dance
24.01.2017 | UT Southwestern Medical Center

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Scientists spin artificial silk from whey protein

X-ray study throws light on key process for production

A Swedish-German team of researchers has cleared up a key process for the artificial production of silk. With the help of the intense X-rays from DESY's...

Im Focus: Quantum optical sensor for the first time tested in space – with a laser system from Berlin

For the first time ever, a cloud of ultra-cold atoms has been successfully created in space on board of a sounding rocket. The MAIUS mission demonstrates that quantum optical sensors can be operated even in harsh environments like space – a prerequi-site for finding answers to the most challenging questions of fundamental physics and an important innovation driver for everyday applications.

According to Albert Einstein's Equivalence Principle, all bodies are accelerated at the same rate by the Earth's gravity, regardless of their properties. This...

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Breaking the optical bandwidth record of stable pulsed lasers

24.01.2017 | Physics and Astronomy

Choreographing the microRNA-target dance

24.01.2017 | Life Sciences

Spanish scientists create a 3-D bioprinter to print human skin

24.01.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>