A team of pshysicists and biologists at Delft University have solved one of the puzzles of chromosome formation during cell division.
They managed to film condensin (the protein complex involved) in action, as it processed to DNA strands into loops.
Scientists have long wondered, whether condensin 'scrapes DNA together' from the cell, or rather uses a 'needle and thread' technique to form the loops of DNA that compact into chromosomes.
Their video and measurement now prove it to be the latter.
Condensin binds to the DNA, and coils it up in some kind of lasso technique, forming loops that are consequently packed into tight sausages, the choromosomes.
Team leader Cees Dekker, professor in molecular physics at TU Delft says the team learned a lot about the process the making of those loops.
For example, loops are made at a speed of 1500 DNA letters per second, and the process is asymmetrical. The protein complex only exerts force on one side of the DNA string.
Experts are enthousiastic.
"It is very likely that a cell uses this looping strategy more often. Condensin is part of a family of protein complexes that involve similar tasks. It is likely other complexes use the same looping mechanism to give structure to DNA. It could shed more light on gene expression. Knowing how and where proteins grab the DNA is important. A defect in the mechanism could also be the cause of some cancers. It really is a major breakthrough", says Benjamin Rowland of the Dutch Cancer Institute.
"The most important thing about it is just the fundamental knowledge", says team leader Dekker. "The cell has a really elegant way to organize DNA. And now we can see it with our own eyes!"
https://www.delta.tudelft.nl/article/how-fit-two-metres-dna-six-micrometre-nucleushttps://youtu.be/zd2I-Yq_35Yhttps://youtu.be/3rB7RchZ2ewhttps://youtu.be/Ce7gMNAOI1A
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