Nature · 9 authors, 3 centres
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Using single-molecule imaging, this in vitro study demonstrates that the Smc5/6 complex actively extrudes DNA loops symmetrically at a force-dependent rate of approximately one kilobase pair per second, establishing loop extrusion as a shared mechanism across all three eukaryotic SMC complexes.
This study used single-molecule imaging to investigate the biochemical activity of the Smc5/6 complex on DNA. The authors found that Smc5/6 actively extrudes DNA loops symmetrically upon ATP hydrolysis, at a force-dependent rate of approximately one kilobase pair per second. Loop extrusion is carried out by Smc5/6 dimers, while monomeric Smc5/6 translocates unidirectionally along DNA without extruding loops. The Nse5/6 subcomplex was identified as a negative regulator that inhibits loop-extrusion initiation by hindering Smc5/6 dimerization, but does not affect ongoing extrusion. These results establish DNA loop extrusion as a conserved mechanism shared among all three eukaryotic SMC complexes (cohesin, condensin, and Smc5/6).
