ASYMMETRY: Researchers anchored a DNA strand to a quartz surface using streptavidin and watched as the protein complex condensin latched to the nucleic acid and formed loops. Contrary to previously established computational models of loop extrusion, which predicted that the two sides of the DNA strand would be reeled in simultaneously, findings from this study suggest that condensin anchors itself to a piece of DNA and reels in the other side.
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© IKUMI KAYAMA/STUDIO KAYAMA
The paper
M. Ganji et al., “Real-time imaging of DNA loop extrusion by condensin,” Science, doi:10.1126/science.aar7831, 2018.
How does a human cell neatly pack more than 2 meters’ worth of DNA into 46 tiny chromosomes? One popular theory is that, with the help of a large protein complex known as condensin, DNA forms many compact loops.
One of the earliest pieces of evidence for this process arrived in the 1970s, when a pair of biochemists observed loops of DNA in electron micrographs of HeLa chromosomes. Researchers later pinpointed condensin as a key protein complex involved in forming these structures, yet “how it works has been completely unknown,” says Christian Häring, who investigates chromosome structure and dynamics at the European Molecular Biology Laboratory in Germany. Some scientists ...
