Researchers at Kavli Institute of Delft University and EMBL Heidelberg have filmed a protein apparatus manipulating the shape of DNA. In the video, a condensin complex remains bound at the stem of a piece of DNA, which it pulls into a loop. This mechanism is vital to the cell’s ability to neatly package meters-long strands of DNA base pairs into compact chromosomes only a few micrometers in size.
Mahipal Ganji, a biophysicist at Delft University, and colleagues reported in Science on February 22 that they first tethered two ends of a piece of DNA to a surface and observed the condensin complex as it moved along the strand, pulling DNA into a loop at a rate of about 0.6 kilobase pairs per second.
M. Ganji et al., “Real-time imaging of DNA loop extrusion by condensin,” Science, doi:10.1126/science.aar7831, 2018.