Cohesin - A Molecular Motor that Folds Our Genome

Arthur T Knackerbracket has found the following story:

New insights into the process of DNA-looping change our view of how the genome is organised within cells. The discoveries by IMP-researchers elucidate a fundamental mechanism of life and settle a decade long scientific dispute.

To pack the genetic information, inscribed in roughly two metres of DNA, into its nucleus, a human cell must achieve the equivalent of fitting an 80-kilometre-long thread into a sphere the size of a soccer ball. Looking through his microscope back in 1882, German biologist Walther Flemming already glimpsed at how this trick is done. What he saw were loops of DNA-strands inside the nucleus of an egg-cell that reminded him of the brushes that were used at the time to clean gas lanterns - and so he named these structures lampbrush chromosomes, without an idea of what they were and which purpose they served.

It took many decades to identify the lampbrush chromosomes as strands of DNA neatly folded into loops, even longer to realise that DNA is folded into such structures in all cells and at all times, and it took until now to find out how this folding is done. In a paper published by the journal Science, researchers from Jan-Michael Peters' lab at the Institute of Molecular Pathology (IMP) in Vienna demonstrate for the first time that a molecular machine actively and purposefully folds DNA via "loop extrusion" and thereby fulfils several important functions in the interphase cell.

That the process of looping DNA is neither random nor arbitrary is evident from how evolutionary ancient it is. All organisms do it, from bacteria to humans. The primeval function of the folding mechanism is still unknown and we may never find out, but some vital tasks have been discovered in recent years. By looping DNA, distant regions on the large molecule are brought into close proximity and are able to interact. This physical contact plays an important role in gene regulation, where DNA segments called enhancers influence which genes are active. Looping is also essential for the ability of immune cells to produce a diverse array of antibodies.

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