Constant overlap: Scientists identify molecular machinery that maintains important feature of the spindle

Aug 06, 2010

During cell division, microtubules emanating from each of the spindle poles meet and overlap in the spindle's mid zone. Scientists at the European Molecular Biology Laboratory (EMBL) in Heidelberg, Germany, have uncovered the molecular mechanism that determines the extent of this overlap. In a study published today in Cell, they were able to reconstruct such anti-parallel microtubule overlaps in vitro, and identify two proteins which are sufficient to control the formation and size of this important spindle feature.

Thomas Surrey and his group at EMBL found that one protein, PRC1, bundles together microtubules coming from opposite ends of the cell, attaching them to each other. It then recruits a second protein, a molecular motor from the kinesin-4 subfamily, increasing its concentration in the spindle mid zone. This motor walks along the overlapping microtubules like an officer on patrol, until it reaches one of the ends. When enough kinesin-4 molecules reach the end of the overlap, they inhibit the growth of microtubules there, thus keeping the overlap size constant without affecting microtubules elsewhere in the cell.

The spindle mid zone plays an important role not only in helping to align the in metaphase, but also in the final stages of cell division, when it drives the physical separation of the two daughter-cells. But between these two stages, the two ends of the spindle must move away from each other, to drag half the to each side of the dividing cell.

At this point, if PRC1 and kinesin-4 had stopped microtubule growth permanently in the central part of the spindle, the overlap would become smaller and smaller, until eventually the spindle itself would collapse, jeopardising cell division. But Surrey and colleagues found that PRC1 and kinesin-4 control the overlap size in an adaptive manner. As the spindle stretches and the overlap between microtubules becomes smaller, the scientists posit, the of kinesin-4 diminishes, allowing the microtubule ends to grow.

This video is not supported by your browser at this time.
If both PRC1 and kinesin-4 are present (fist video), microtubules (blue) grow only until their overlap (red/yellow) reaches a certain size, which then remains constant. But if only PRC1 is present, microtubule growth is not inhibited in the overlap region, which becomes bigger and bigger (second video). Video credits: EMBL/P. Bieling

This video is not supported by your browser at this time.

"Our findings show how molecules millionths of millimetres small can control the size of a structure about a thousand times larger than themselves," Surrey concludes: "they help us to understand the fundamentals of ."

Explore further: Genomes of malaria-carrying mosquitoes sequenced

add to favorites email to friend print save as pdf

Related Stories

One-dimensional Diffusion Accelerates Molecular Motors

May 12, 2006

Max Planck scientists have identified a new strategy which motor proteins use to move. The research was carried out by Prof. Jonathon Howard and Stefan Diez at the Max Planck Institute of Molecular Cell Biology ...

A unique arrangement for egg cell division

Aug 09, 2007

Which genes are passed on from mother to child is decided very early on during the maturation of the egg cell in the ovary. In a cell division process that is unique to egg cells, half of the chromosomes are eliminated from ...

Scientists deconstruct cell division

Feb 08, 2009

The last step of the cell cycle is the brief but spectacularly dynamic and complicated mitosis phase, which leads to the duplication of one mother cell into two daughter cells. In mitosis, the chromosomes ...

Dartmouth researchers find new protein function

Jan 09, 2009

A group of Dartmouth researchers has found a new function for one of the proteins involved with chromosome segregation during cell division. Their finding adds to the growing knowledge about the fundamental ...

Recommended for you

Genomes of malaria-carrying mosquitoes sequenced

6 hours ago

Nora Besansky, O'Hara Professor of Biological Sciences at the University of Notre Dame and a member of the University's Eck Institute for Global Health, has led an international team of scientists in sequencing ...

How calcium regulates mitochondrial carrier proteins

Nov 26, 2014

Mitochondrial carriers are a family of proteins that play the key role of transporting a chemically diverse range of molecules across the inner mitochondrial membrane. Mitochondrial aspartate/glutamate carriers are part of ...

Team conducts unprecedented analysis of microbial ecosystem

Nov 26, 2014

An international team of scientists from the Translational Genomics Research Institute (TGen) and The Luxembourg Centre for Systems Biomedicine (LCSB) have completed a first-of-its-kind microbial analysis of a biological ...

Students create microbe to weaken superbug

Nov 25, 2014

A team of undergraduate students from the University of Waterloo have designed a synthetic organism that may one day help doctors treat MRSA, an antibiotic-resistant superbug.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.