In vitro dynamics of DNA loop extrusion by structural maintenance of chromosomes complexes

Genomic DNA inside the cell's nucleus is highly organized and tightly controlled by the structural maintenance of chromosomes (SMC) protein complexes. These complexes fold genomes by creating and processively enlarging loops, a process called loop extrusion. After more than a decade of accumulating indirect evidence, recent in vitro single-molecule studies confirmed loop extrusion as an evolutionarily conserved function among eukaryotic and prokaryotic SMCs. These studies further provided important insights into mechanisms and regulations of these universal molecular machines, which will be discussed in this minireview.