Condensin wraps it up

Packing DNA into a nucleus is no mean feat. Now, David Bazett-Jones (Hospital for Sick Children, Toronto, Canada), Keiji Kimura, and Tatsuya Hirano (Cold Spring Harbor Laboratory, Cold Spring Harbor, NY) have found that a single condensin complex can use ATP to wrap two positive gyres of DNA around itself. That packaging, however, may just be the start.Based on previous experiments, Hirano and colleagues had suggested that an individual condensin might span a considerable distance between DNA binding sites and introduce global writhe that would twist the DNA into a right-handed solenoid. But direct observation of single complexes on naked DNA by electron spectroscopic imaging has now shown that a single complex is instead tightly wrapped with two turns of DNA.

What that means for condensation of cellular chromatin is not yet clear. “We...