Dresden 2020 – scientific programme
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BP: Fachverband Biologische Physik
BP 22: Single Molecule Biophysics (joint session BP/CPP)
BP 22.3: Talk
Wednesday, March 18, 2020, 10:00–10:15, SCH A251
Real-time imaging of DNA loop extrusion by condensin and their mutual interactions — •Eugene Kim1, Jacob Kerssemakers1, Indra Shaltiel2, Christian Haering2, and Cees Dekker1 — 1Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, Netherlands. — 2Cell Biology and Biophysics Unit, Structural and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Heidelberg, Germany.
How is DNA spatially organized in our cells? By what mechanisms do chromosomes fold over long distances? In this talk, I will discuss our work on understanding the looping structures of DNA using fluorescence imaging assay at the single-molecule level. The major focus is on condensin, that is one of the SMC (Structural Maintenance of Chromosomes) complexes. This ring-shaped protein is the molecular motor that can extrude large loops of DNA, a mechanism thought to be the basis of the chromosome structures at various stages of the cell cycle. I will firstly show how a single condensin can extrude loops at a force-dependent speed of up to 2 kbp/s and it does so in a strictly asymmetric manner. I will then show how these individual condensins can form a dimeric structure by traversing one over the other, in turn forming a novel type of loop structure that we name as Z loop. This condensin dimer can extrude DNA in a symmetric fashion, thus may be able to contribute to chromosomal compaction in a more efficient way. We believe that our work will allow to disentangle the fundamental looping architecture of chromosomes, that is essential to all life.