Using magnets and video microscopy to measure the length of individual DNA molecules under experimental conditions, researchers have demonstrated that Condensin, a complex of proteins widely conserved in evolution, physically compacts DNA in a manner dependent on energy from ATP. The finding is significant because the Condensin complex, which is essential for life, has been known to play a key role in the dramatic condensation of genomic DNA that precedes mitosis and cell division. The new work puts into sharper focus the mechanism by which Condensin accomplishes this compaction, which is essential for the precise segregation of the genetic material to later generations of cells.

Scientists Terence Strick, Tatsuhiko Kawaguchi and Tatsuya Hirano of Cold Spring Harbor Laboratory employed a nanomanipulation technique by which small individual molecules of DNA, tethered on one end to a glass slide and attached on the other end to a magnetic bead, could be gently stretched and twisted using small magnets. The technique allowed the researchers to exert controlled, variable force on the extended DNA, directly measuring changes in its compaction following interactions with Condensin complexes isolated from frog eggs. Because the helical DNA could be twisted, the scientists were also able to investigate how DNA topology in this case, topological states called positive and negative supercoiling might affect its ability to be compacted by Condensin. Such measurements are central to illuminating the molecular mechanism used by Condensin in the cell.

The researchers found that Condensin compacts DNA against a weak stretching force, but that increasing the force on the DNA reversed compaction, effectively breaking apart the molecular interactions formed by Condensin. Carefully measuring changes in distance between the two ends of the DNA molecule revealed evidence that both compaction and decompaction often occurred in jumps of certain lengths. Comparing the ran
'"/>

Contact: Heidi Hardman
hhardman@cell.com
617-397-2879
Cell Press
22-Apr-2004

Page: 1 2
Related biology news :

1. Belgian researchers explore revolutionary approach to angiogenesis
2. Award winning researchers reveal potential new role for Glivec
3. $7.5 Million grant to Yale researchers for role of viruses in cancer
4. New anti-inflammatory strategy for cancer therapy identified by UCSD researchers
5. Joslin researchers clarify mechanisms for beta-cell formation
6. Virginia Tech researchers to release findings on Smith River Project
7. Molecular motor myosin VI moves hand over hand, researchers say
8. ASU researchers demonstrate new technique that improves the power of atomic force micrscopy
9. Emory researchers map structure of anti-cancer molecule
10. Leukemia stem cells identified by Stanford researchers
11. EURYI Award given for the first time to 25 young European researchers