Compaction of double-stranded DNA by negatively charged proteins and colloids

• Depletion of DNA in solutions of anionic crowding agents is highlighted.
• Single-molecule DNA conformational dynamics is revealed.
• The effect of confinement on DNA compaction by crowding agents is explained.

A great number of past in vivo and in vitro studies on DNA condensation/compaction made clear DNA conformational behavior and its influence on DNA bioactivity in systems containing either polymers or colloids which are positively charged or electrically neutral. However, there still remains a lack of understanding about interaction between DNA and like-charged species. Such knowledge is important for deeper insight into DNA behavior in cellular environment, where DNA encounters negatively charged biopolymers such as RNA and RNase at relatively high concentrations, and should contribute to an overall understanding of the intrinsic mechanism that underlies the spatiotemporal dynamics of biomacromolecules in various cellular processes. In this review, we focus on DNA condensation/compaction by negatively-charged species, compare it with established earlier model systems of DNA condensation/compaction, and discuss recent advances in the field. We show that DNA compaction by negatively charged polymers and colloids exhibits some similarities with that induced by neutral polymers, but stress that several new features imposed by the electrostatics of polyanions should be considered to grasp the whole picture.

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