Oligomerization and ATP stimulate condensin-mediated DNA compaction

Area of Science:

• Molecular Biology
• Cell Biology
• Biophysics

Background:

• Condensin is a heteropentameric enzyme responsible for large-scale chromatin remodeling during mitosis.
• The precise mechanism by which condensin utilizes ATP hydrolysis for chromosome compaction and segregation is not fully understood.

Purpose of the Study:

• To investigate the DNA-organizing mechanism of yeast condensin, focusing on its different configurations.
• To elucidate the role of condensin oligomerization in ATP-dependent DNA compaction.

Main Methods:

• Purification of budding yeast condensin to identify different oligomeric states.
• Single-DNA magnetic tweezers assay to measure DNA compaction by yeast condensin.
• Analysis of compaction dynamics under varying forces and DNA torsional stress.

Main Results:

• Budding yeast condensin exists in both heteropentameric and larger oligomeric forms.
• Only oligomerized condensin exhibits ATP-enhanced DNA compaction.
• Compaction occurs in step-like events of ~200 nm, suppressed by forces >1 pN, and is largely insensitive to torsional stress.

Conclusions:

• Oligomerized condensin plays a physiological role in gradual chromatin compaction during mitosis.
• The observed step-like dynamics are consistent with a loop-extrusion mechanism for DNA compaction and organization.