Study: Molecular motors shape chromosome structure
Human cells contain 23 pairs of chromosomes that form a loosely organized cluster in the cell nucleus. When cells divide, they must first condense these chromosomes — each of which when fully extended is a thousand times longer than the cell’s nucleus and physically indistinguishable from the others — into compact structures that can be easily separated and packaged into their offspring. An MIT-led team has now developed a model that explains how cells handle this difficult task. In computer simulations, the researchers demonstrate that certain molecular “machines” can transform chromosomes from a loosely tangled rope into a series of tiny loops that condense each chromosome and allow it to extricate itself from the others. Moreover, the researchers demonstrate that a similar model explains how chromosomes are organized when cells are not dividing, and they hypothesize that loop extrusion by molecular motors splits chromosomes into separate domains, helping to control which genes...