Structural insights into DNA loop extrusion by SMC protein complexes.

Structural Maintenance of Chromosomes (SMC) protein complexes play key roles in the three-dimensional organization of genomes in all kingdoms of life. Recent insights from chromosome contact mapping experiments and single-molecule imaging assays suggest that these complexes achieve distinct cellular functions by extruding large loops of DNA while they move along the chromatin fiber. In this short review, we summarize recent insights into the molecular architecture of these unconventional DNA motor complexes, their interaction with their DNA substrates, and the remarkable dynamic changes they can undergo during their ATPase reaction cycle.