Biological complexity: how cells can repair broken DNA (Introduction)

by David Turell , Sunday, February 09, 2020, 16:05 (1539 days ago) @ David Turell

Using filaments in a special mechanism:

https://www.sciencedaily.com/releases/2020/02/200205132349.htm

"An elaborate system of filaments, liquid droplet dynamics and protein connectors enables the repair of some damaged DNA in the nuclei of cells, researchers 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.

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"DNA repair helps ensure genome stability, which in turn allows cells to function and promotes health in all organisms. 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.

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"'The liquid droplets work with intranuclear microtubules to promote the clustering of damaged DNA sites," says Mekhail, an associate professor of laboratory medicine and pathobiology at U of T. "Repair proteins at these different sites assemble in droplets that fuse into a larger repair-centre droplet, through the action of the shorter nuclear microtubules."

"This larger oil-like droplet then behaves like a spider, says Mekhail, shooting out a web of star-shaped filaments that tether to the longer autobahns along which damaged DNA can be transported to the DNA hospitals.

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"After months of talks and experiments, computer simulations repeatedly predicted that the shorter filaments would move like pistons, lowering pressure in the nucleoplasm and creating a suction effect that leads to the fusion of droplets. Mekhail and his team confirmed that finding in their lab.

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"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."

Comment: In analyzing very complex systems of this sort, which are so protective in maintaining vital functioning structures, we could ask, "which came first, chicken or egg?". Answer: "both". DNA cannot be placed in charge unless its protections are also put in place at the same time. Simultaneous appearance requires design and its designer's mental activity.

This is why the so-called RNA world start to life is ludicrous. Part of a cell is not life. Life requires wholly active intact cells with all their parts. Initial real life was cells.

So is life a stupendous natural miracle, or a creation by a designer? The answer is obvious.