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 Flavins keep a handy helper in their pocket
25.04.2018 | University of Freiburg

nachricht Complete skin regeneration system of fish unraveled
24.04.2018 | Tokyo Institute of Technology

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: BAM@Hannover Messe: innovative 3D printing method for space flight

At the Hannover Messe 2018, the Bundesanstalt für Materialforschung und-prüfung (BAM) will show how, in the future, astronauts could produce their own tools or spare parts in zero gravity using 3D printing. This will reduce, weight and transport costs for space missions. Visitors can experience the innovative additive manufacturing process live at the fair.

Powder-based additive manufacturing in zero gravity is the name of the project in which a component is produced by applying metallic powder layers and then...

Im Focus: Molecules Brilliantly Illuminated

Physicists at the Laboratory for Attosecond Physics, which is jointly run by Ludwig-Maximilians-Universität and the Max Planck Institute of Quantum Optics, have developed a high-power laser system that generates ultrashort pulses of light covering a large share of the mid-infrared spectrum. The researchers envisage a wide range of applications for the technology – in the early diagnosis of cancer, for instance.

Molecules are the building blocks of life. Like all other organisms, we are made of them. They control our biorhythm, and they can also reflect our state of...

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Getting electrons to move in a semiconductor

25.04.2018 | Physics and Astronomy

Reconstructing what makes us tick

25.04.2018 | Physics and Astronomy

Cheap 3-D printer can produce self-folding materials

25.04.2018 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>