Biological complexity: cell division DNA controls (Introduction)

by David Turell , Thursday, September 07, 2017, 19:32 (2415 days ago) @ David Turell

How the chromosomes are herded into two cells. A control protein is found:

https://phys.org/news/2017-09-chromosome-motor-discovery-dna-loop.html

"How does a cell neatly distribute its replicated DNA between two daughter cells? For more than a century, we have known that DNA in the cell is comparable to a plate of spaghetti—a jumble of intermingled strands. When cells divide, they have to pack two metres of DNA into tidy little packages—chromosomes. This packing is induced by proteins called condensin, but scientists are split regarding the actual mechanism. One argument holds that the protein works like a hook, randomly grasping somewhere in the jumble of DNA and tying it all together. Another holds that the ring-shaped protein pulls the DNA inward to create a loop. In a new study reported in Science, researchers from TU Delft, Heidelberg and Columbia University give the oop-extrusion argument a significant boost, demonstrating that condensin does, indeed, have the putative motor function required for this dynamic.

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"In their article in Science, the researchers show for the first time that condensin does have a motor function. They positioned DNA molecules that were stretched on a surface and added condensin proteins, each fitted with a light-emitting quantum dot to enable observation. "We observed how condensin does, indeed, translocate along the DNA. This only happened if fuel was present, in this case the molecule ATP – the petrol that powers all processes in a cell," explains Jorine Eeftens, graduate student at Delft and one of the first authors. "The results also show that condensin takes extremely large steps on the DNA, and therefore needs significantly less ATP than previously thought." In the second stage of their research, the researchers replaced the light-emitting quantum dot on the condensin with a light-emitting string of DNA. They once again witnessed condensin moving in the same way. Condensin is therefore able to move a piece of DNA in relation to another, which corresponds with the idea of loop formation.

"'The exact underlying mechanism is still open to discussion. But this discovery is certainly an enormous boost to the loop extrusion camp. We have also shown that the amount of energy used is a lot less than previously thought," says Cees Dekker.

"The research represents a significant step in the fundamental understanding of cells, but it is also relevant for medical research. Problems with the protein family to which condensin belongs, the SMC proteins, are related to hereditary conditions such as Cornelia de Lange Syndrome. Condensin is also crucial in the organisation of the chromosomes during cell division, and errors in the process can result in cancer. A better understanding of these processes is vital for tracking down the molecular origins of serious illnesses."

Comment: With enough advances in research into cell division and reproduction we might be able tp solve the congenital defects like Down's syndrome, an issue dhw raised today. Again this research demonstrates how complex is our biology has to be. Not by chance.