The condensin complex is a mechanochemical motor that translocates along DNA

Abstract

Condensin plays crucial roles in chromosome organization and compaction, but the mechanistic basis for its functions remains obscure. We used single-molecule imaging to demonstrate that Saccharomyces cerevisiae condensin is a molecular motor capable of adenosine triphosphate hydrolysis–dependent translocation along double-stranded DNA. Condensin’s translocation activity is rapid and highly processive, with individual complexes traveling an average distance of ≥10 kilobases at a velocity of ~60 base pairs per second. Our results suggest that condensin may take steps comparable in length to its ~50-nanometer coiled-coil subunits, indicative of a translocation mechanism that is distinct from any reported for a DNA motor protein. The finding that condensin is a mechanochemical motor has important implications for understanding the mechanisms of chromosome organization and condensation.

Condensin controls mitotic chromosome stiffness and stability without forming a structurally contiguous scaffold

“…Even without any cooperative interaction between SMCs, “loop-extrusion” dynamics could drive condensin accumulation at the bases of chromatin loop domains while compacting chromosomes (Alipour and Marko, 2012, Goloborodko et al, 2016b, Goloborodko et al, 2016a). Single-molecule experiments have indeed observed DNA translocation (Terakawa et al, 2017) and loop-extrusion (Ganji et al, 2018) dynamics for yeast condensin, supporting this model. A possible molecular mechanism underlying loop extrusion by condensin which is consistent with the observations of (Ganji et al, 2018) has been presented in (Lawrimore et al, 2017).…”

Single molecule tracking reveals that the bacterial SMC complex moves slowly relative to the diffusion of the chromosome

“…Indeed, it has been shown that condensin from Saccharomyces cerevisiae is a molecular motor capable of ATP hydrolysis-dependent translocation along double-stranded DNA in vitro , using DNA curtains at a velocity of ∼60 base pairs per second (60). An argument against this model is the relative low ATPase activity of Smc (3) compared to other nucleic acid motor proteins.…”

DNA entry, exit and second DNA capture by cohesin: insights from biochemical experiments

“…Purified budding yeast condensin promotes the formation and enlargement of DNA loops in an ATP-dependent manner [81]. In a different experimental setting, condensin has also been shown to translocate along DNA unidirectionally, which requires its intact ATPase [82]. These studies have suggested that condensin functions as an active machine to mediate DNA loop extrusion.…”

“…However, in contrast to budding yeast condensin, ATP-dependent, unidirectional translocations have not been seen for both the fission yeast and human cohesins [19,20,50]. It should also be noted that the purified budding yeast condensin can tether two intermolecular DNA strands [82]. Thus, cohesin and condensin might be equipped with activities for both stochastic interactions and loop extrusions.…”