Challenging the belief that DNA “floats aimlessly”:
An elaborate system of filaments, liquid droplet dynamics and protein connectors enables the repair of some damaged DNA in the nuclei of cells, researchers at the University of Toronto have found. The findings further challenge the belief that broken DNA floats aimlessly — and highlight the value of cross-disciplinary research in biology and physics.
Double-strand DNA breaks are especially toxic to cells, and researchers had assumed for decades that these breaks floated inside cell nuclei without direction, until they trigger other cellular changes or happen on a fixer mechanism.
That thinking began to change in 2015, when Karim Mekhail and his lab showed that damaged DNA can be intentionally transported by motor protein ‘ambulances’ to DNA ‘hospitals,’ areas enriched with certain repair factors in the nuclei. The researchers later worked with U of T aerospace engineers to show that after a single double-strand break, DNA travels for repair via long ‘autobahns’ of thread-like microtubules, which are also moving…
The most surprising finding came after several cycles of droplet fusion, the researchers found. “It was very bizarre and totally unexpected, I still remember the day,” Mekhail says. Oshidari observed that the larger droplets initiate an internal concentration of filament building blocks, forcing creation of a kind of self-interlocking brick road, which together with the spidery webs allow DNA to hook onto the longer autobahn filaments.
The complex process is easy to miss when looking at DNA damage sites, says Mekhail, largely because imaging in the field has become highly automated. Most software has been set up to see what has already been seen. “We can’t rely on the old ways of observing,” he says. “We need to update our software and also go back to looking with the human eye, guided by simulations when needed.” University of Toronto, “Genome stability: Intricate process of DNA repair discovered” at ScienceDaily
The researchers, fearing that their media release was too long already, never got around to explaining intracellular health care policy, which would have easily run to 30,000 pages of administrese… 😉
Funny how the new finds never seem to support natural selection acting on random mutations (Darwinism) but always intricate nests of patterns inside patterns.
Hat tip: Philip Cunningham