Anatomy of a flexer-DNA complex inside a higher-order transposition intermediate

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• Escherichia coli HU is a nonsequence-specific DNA-binding protein crucial for DNA organization.
• Understanding HU's role in complex structures like the Mu transpososome is vital for DNA replication and transposition.
• Previous studies lacked precise data on HU's localization and DNA interaction within the Mu transpososome.

Purpose of the Study:

• To determine the precise localization, stoichiometry, and orientation of HU binding within the Mu transpososome.
• To characterize the DNA bending induced by HU binding in the Mu transpososome.
• To generate a molecular model of the HU-DNA interaction within the transpososome.

Main Methods:

• Chemical modification of Escherichia coli HU protein to create 16 distinct HU-nucleases with iron-EDTA cleavage moieties.
• Analysis of specific DNA cleavage patterns generated by each HU-nuclease within the Mu transpososome.
• Integration of DNA cleavage data with HU's 3D structure for computational molecular modeling.

Main Results:

• Specific DNA cleavage patterns precisely mapped HU binding sites, stoichiometry, and orientation in the Mu transpososome.
• HU binding induces a significant DNA bend, with its center, direction, and magnitude quantified.
• The study provides the first molecular model snapshot of HU-DNA interaction within the Mu transpososome.

Conclusions:

• HU-nucleases are effective tools for dissecting protein-DNA interactions in complex molecular machines.
• HU binding plays a critical role in shaping DNA within the Mu transpososome, inducing a pronounced bend.
• The derived HU-DNA interaction model offers new insights into the mechanism of DNA transposition.