Binds tightly to dsDNA (PubMed:10844682). Acts as a global transcriptional regulator through its ability to bind to AT-rich DNA sequences (PubMed:1423593, PubMed:16933988, PubMed:21673140). Binds in the minor groove of AT-rich DNA (PubMed:21673140). Was found to bind 746 genes, about half of which show no change in expression in disruption experiments suggesting these sites are important for nucleoid structure (PubMed:16933988). On a global level genes bound by H-NS are expressed at a lower than average level; H-NS is excluded from binding to highly transcribed genes and does not co-localize with RNA polymerase in DNA-binding studies during exponential growth in rich medium (PubMed:16933988). The best correlation for H-NS binding is AT-content rather than predicted DNA curvature (PubMed:16933988). Has a strong preference for DNA that has been recently acquired by horizontal gene transfer, binding strongly to Salmonella pathogenicity islands 1 and 2 (SPI1 and SPI2); this offers the selective advantage of silencing foreign DNA while keeping it in the genome in case of need (PubMed:16933988). DNA-binding influences plasmid DNA topology (PubMed:1423593). For the proU locus (the proV-proW-proX operon) inhibits transcription at low osmolarity by binding to AT-rich, curved, DNA downstream of the transcription start site of proV; repression is greater when more than 1 curved DNA sequence is present (PubMed:1423593). It plays a role in the thermal control of pili production (By similarity). It is subject to transcriptional auto-repression (By similarity). It binds preferentially to the upstream region of its own gene recognizing two segments of DNA on both sides of a bend centered around -150 (By similarity). Forms oligomers of increasing size with increasing protein concentration (PubMed:10844682, PubMed:23515315). The fragment of 1-83 probably forms oligomers of 4 dimeric units at 10 degrees Celsius, at 40 degrees Celsius only dimers are formed (PubMed:20798056). Binds Hha and YdgT (also known as cnu); crystal structures suggest each H-NS dimer could bind 2 Hha monomers on opposites sides (PubMed:23515315). Probably also binds StpA (By similarity). Composed of 2 domains (approximately residues 1-64 and 89-136) joined by a flexible linker. The isolated N-terminus (1-64) forms a trimer, probably via coiled-coil interactions (PubMed:10844682, PubMed:11237622). The isolated N-terminus plus linker fragment (residues 1-89) forms homooligomers of increasing size with increasing protein concentration, while the isolated C-terminus fragment is a monomer (PubMed:10844682). A shorter fragment (residues 1-46) interacts with Hha (PubMed:23515315). Loss of osmotic regulation of the proU locus, loss of changes in plasmid linking number (PubMed:1423593). 2X decreased growth rate, which is partially restored by a mutation preventing expression of SPI2, increased expression of about half of the genes to which H-NS binds (PubMed:16933988). Note strain LT2 has point mutation in rpoS which decreases its translation efficiency, in the presence of wild-type rpoS, deletion of hns is lethal (PubMed:16933988). Belongs to the histone-like protein H-NS family.