Getting chromosomes into shape using rings and sticks

Faithful distribution of the genetic material during cell division relies on the folding of DNA into discrete and compact bodies called chromatids. SMC protein complexes have evolved to deal with the tangly nature of long DNA molecules. They act as molecular clamps that bring together selected DNA segments. The researchers determined the architecture of the ancestral SMC complex and elucidated its dynamic localization on the bacterial chromosome. The results indicate that SMC rings are not merely DNA linkers but active machines, which step-by-step enlarge DNA loops to organize chromosomes.