  Hfq is a bacterial protein that is involved in several aspects of nucleic
acids metabolism. It has been described as one of the nucleoid associated
proteins shaping the bacterial chromosome, although it is better known to
influence translation and turnover of cellular RNAs. Here, we explore the role
of Escherichia coli Hfq C-terminal domain in the compaction of double stranded
DNA. Various experimental methodologies, including fluorescence microscopy
imaging of single DNA molecules confined inside nanofluidic channels, atomic
force microscopy, isothermal titration microcalorimetry, and electrophoretic
mobility assays have been used to follow the assembly of the C-terminal and
N-terminal regions of Hfq on DNA. Results highlight the role of Hfq C-terminal
arms in DNA binding, change in mechanical properties of the double helix and
compaction of DNA into a condensed form. The propensity for bridging and
compaction of DNA by the C-terminal domain might be related to aggregation of
bound protein and may have implications for protein binding related gene
regulation.
