Abstract
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.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adenosine Triphosphatases / chemistry
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Adenosine Triphosphatases / genetics
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Adenosine Triphosphatases / metabolism*
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Adenosine Triphosphate / chemistry
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Adenosine Triphosphate / metabolism*
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Cell Cycle Proteins / chemistry
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Cell Cycle Proteins / genetics
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Cell Cycle Proteins / metabolism
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Chromosomal Proteins, Non-Histone / chemistry
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Chromosomal Proteins, Non-Histone / genetics
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Chromosomal Proteins, Non-Histone / metabolism*
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Chromosomes, Fungal / metabolism*
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Chromosomes, Fungal / ultrastructure
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DNA, Fungal / chemistry
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DNA, Fungal / genetics
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DNA, Fungal / metabolism*
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DNA-Binding Proteins / chemistry
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism*
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Fungal Proteins / chemistry
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Fungal Proteins / genetics
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Fungal Proteins / metabolism*
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Gene Expression
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Microscopy, Atomic Force
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Multiprotein Complexes / chemistry
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Multiprotein Complexes / genetics
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Multiprotein Complexes / metabolism*
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Nuclear Proteins / chemistry
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism
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Nucleic Acid Conformation
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Protein Binding
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Protein Conformation
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae / metabolism*
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Saccharomyces cerevisiae / ultrastructure
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Saccharomyces cerevisiae Proteins / chemistry
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Saccharomyces cerevisiae Proteins / genetics
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Saccharomyces cerevisiae Proteins / metabolism
Substances
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Cell Cycle Proteins
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Chromosomal Proteins, Non-Histone
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DNA, Fungal
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DNA-Binding Proteins
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Fungal Proteins
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Multiprotein Complexes
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Nuclear Proteins
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SMC2 protein, S cerevisiae
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SMC4 protein, S cerevisiae
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Saccharomyces cerevisiae Proteins
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condensin complexes
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Adenosine Triphosphate
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Adenosine Triphosphatases