Human Condensin I and II Drive Extensive ATP-Dependent Compaction of Nucleosome-Bound DNA

Summary

Structural maintenance of chromosomes (SMC) complexes are essential for genome organization from bacteria to humans, but their mechanisms of action remain poorly understood. Here, we characterize human SMC complexes condensin I and II and unveil the architecture of the human condensin II complex, revealing two putative DNA-entrapment sites. Using single-molecule imaging, we demonstrate that both condensin I and II exhibit ATP-dependent motor activity and promote extensive and reversible compaction of double-stranded DNA. Nucleosomes are incorporated into DNA loops during compaction without being displaced from the DNA, indicating that condensin complexes can readily act upon nucleosome-bound DNA molecules. These observations shed light on critical processes involved in genome organization in human cells.

Graphical Abstract

Highlights

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  Architecture of ATPγS-bound human condensin II

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  Human condensin II possesses two putative DNA binding compartments

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  Human condensins drive robust ATP-dependent compaction of nucleosome-bound DNA

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  Loop extrusion by human condensins can be symmetric or asymmetric

Abstract

Kong and Cutts et al. present the general architecture of ATPγS-bound human condensin I and II complexes. They demonstrate that both human condensins are ATP-dependent motors that drive robust compaction of nucleosome-bound DNA, in either a symmetric or asymmetric manner, supporting the loop extrusion model under physiological conditions in higher eukaryotes.