The condensin holocomplex cycles dynamically between open and collapsed states.

Structural maintenance of chromosome (SMC) protein complexes are the key organizers of the spatiotemporal structure of chromosomes. The condensin SMC complex has recently been shown to be a molecular motor that extrudes large loops of DNA, but the mechanism of this unique motor remains elusive. Using atomic force microscopy, we ...
show that budding yeast condensin exhibits mainly open 'O' shapes and collapsed 'B' shapes, and it cycles dynamically between these two states over time, with ATP binding inducing the O to B transition. Condensin binds DNA via its globular domain and also via the hinge domain. We observe a single condensin complex at the stem of extruded DNA loops, where the neck size of the DNA loop correlates with the width of the condensin complex. The results are indicative of a type of scrunching model in which condensin extrudes DNA by a cyclic switching of its conformation between O and B shapes.
Mesh Terms:
Adenosine Triphosphatases, Adenosine Triphosphate, Cell Cycle Proteins, Chromosomal Proteins, Non-Histone, Chromosomes, Fungal, DNA, Fungal, DNA-Binding Proteins, Fungal Proteins, Gene Expression, Microscopy, Atomic Force, Multiprotein Complexes, Nuclear Proteins, Nucleic Acid Conformation, Protein Binding, Protein Conformation, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins
Nat Struct Mol Biol
Date: Dec. 01, 2019
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