RETRACTED: The bacterial condensin MukBEF compacts DNA into a repetitive, stable structure

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• Condensins, proteins with structural maintenance of chromosomes (SMC) moieties, are crucial for organizing and compacting chromosomes.
• The precise mechanism by which condensins achieve chromosome compaction and partitioning remains largely unknown.
• MukBEF is the specific condensin complex found in Escherichia coli.

Purpose of the Study:

• To elucidate the mechanism by which MukBEF compacts a single DNA molecule.
• To investigate the structural properties and dynamics of MukBEF-mediated DNA condensation.
• To propose a model for in vivo bacterial chromosome organization by MukBEF.

Main Methods:

• Utilizing single-molecule DNA stretching experiments to analyze MukBEF-DNA interactions.
• Investigating the role of adenosine triphosphate (ATP) binding in the condensation process.
• Observing DNA filament extension and recondensation dynamics under varying forces and conditions.
• Assessing the effect of topoisomerase I on MukBEF-DNA complex behavior.

Main Results:

• MukBEF cooperatively compacts DNA into an ordered, repetitive filament in an ATP-dependent manner.
• Stretching the MukBEF-DNA filament to ~17 piconewtons induced repetitive transitions centered on 45 nm.
• The filament exhibited reversible extension and recondensation cycles, even without ATP or free MukBEF.
• The observed condensation pattern was highly reproducible across multiple cycles and independent of prior deformation.
• Topoisomerase I facilitated reversible extension and recondensation, suggesting trapped supercoiled DNA.

Conclusions:

• MukBEF establishes a stable, self-organizing DNA structure with remarkable elasticity and memory.
• The observed reversible cycles suggest a dynamic yet stable mechanism for DNA compaction.
• The findings support a new model for MukBEF's role in organizing the bacterial chromosome.
• Topoisomerase I interaction highlights the role of DNA topology in MukBEF-mediated organization.