Bridging DNA contacts allow Dps from E. coli to condense DNA

Area of Science:

• Microbiology
• Biochemistry
• Structural Biology

Background:

• DNA-binding protein from starved cells (Dps) is vital for bacterial survival under stress.
• Dps forms nucleoid-associated biomolecular condensates with DNA in vivo.
• Purified Dps rapidly forms large complexes with DNA in vitro, but nucleation mechanisms are unclear.

Approach:

• Investigated the influence of DNA topology on Dps-DNA complex formation.
• Utilized in vitro assays to observe Dps-DNA interactions.
• Analyzed the role of DNA supercoiling and bridging contacts.

Key Points:

• DNA supercoils serve as preferred templates for Dps condensate nucleation.
• Bridging DNA contacts significantly facilitate Dps complex nucleation.
• Dps shows low affinity for relaxed, linear DNA before condensation.
• Condensed DNA-DNA complexes are stable, even without free Dps.

Conclusions:

• DNA topology, particularly supercoiling and bridging contacts, is critical for Dps nucleation.
• Bridging contacts are essential for both nucleating and stabilizing Dps-DNA complexes.
• Understanding these interactions provides insight into bacterial stress adaptation mechanisms.