During cell division, four-meter DNAIt packs into 46 tiny packages (chromosomes) that are only a few millionths of a meter long. In a new study, researchers at the European Molecular Biology Laboratory and the University of Würzburg have shown how motor proteins package DNA strands into compact chromosomes during division.
Geneticists investigated condensin, a proteincomplex that is used in the formation of chromosomes. The scientists conducted a series of experiments that included observing individual condensin molecules as DNA loops formed. The results showed that different parts of the complex act like a complex "molecular machine". One part of this protein holds the DNA in a stable state, like an anchor, while the other part moves the DNA forward like a tractor, thereby creating a wide loop.
The authors of the work say that condensin, likeother motor proteins, makes "steps" along the DNA, while burning cellular energy in the form of ATP. However, burning the same amount of energy, these molecules move 500 times more than other motor proteins. According to the researchers, this effect can be compared to a racing car, whose energy efficiency is comparable to an e-bike.
Using cryoelectron microscopy, geneticists have visualized the complex mechanism of chromosome formation in unprecedented detail.
The researchers note that condensin wasdiscovered over three decades ago, but its mechanism of action has remained largely obscure. This is one of the most ancient protein complexes.
Geneticists believe that the results of the work will helpbetter understand not only the processes of cell division, but also other motor proteins. They say such loops and their associated molecular machines are involved in various genomic processes, including controlling how genes are turned on and off between cell divisions.
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