suggested that StpA may regulate the expression of a tributyltin-inducible operon [1] Currently, no inducer for this regulator has been reported in the literature. New genes may be identified by high-throughput analysis [16] It is a DNA-binding protein with similarity to H-NS [17, 18] and these two proteins can have similar functions [8, 19] It has an approximately fivefold-greater affinity for DNA than H-NS and has a preference for curved DNA [20] This regulator binds curved DNA, in the promoter region, with AT-rich motifs, and StpA binds to sites that have poorly related sequences and it does not have a consensus sequence for the DNA binding. Expression of stpA from a plasmid can complement an hns mutant phenotype and StpA is able to repress and activate a subset of H-NS-regulated genes, but their specific mechanisms remain to be determined [16, 17, 20, 21, 21, 22] A dominant negative form of StpA can disrupt H-NS activity and vice versa, and H-NS can interact with StpA at two distinct domains to form heterodimers in vitro; also there exists evidence that some of these proteins can form homodimers [23, 24, 24, 25] For this reason, in the absence of H-NS the StpA protein is rapidly degraded in a Lon protease-dependent manner [23, 26] protection from proteolytic degradation appears to be mediated by direct interaction between StpA and H-NS [23] On the other hand StpA may form heteromeric complexes with Hha and YdgT [27] StpA and Hha stimulate pausing by RNA polymerase at 20^oC by promoting DNA-DNA bridging of H-NS filaments, through H-NS-mediated gene regulation [28] StpA consists of two structured domains which are separated by a protease-sensitive linker [29] The N-terminal domain is involved in the protein-protein interaction, while the purified C-terminal domain alone promotes annealing of RNA oligonucleotides and trans-splicing in vitro [24, 25, 29, 30] Repression of the bglG operon by StpA occurs as a molecular adapter [13, 14]and only in the presence of the N-terminal H-NS protein domain, which comprises the core for dimerization [9] StpA has RNA chaperone activity in vitro and in vivo, and the RNA chaperone activity of StpA is influenced by the structural stability of the RNA target molecule [12, 22, 30, 31, 32, 33, 34] StpA may destabilize the small regulatory RNA MicF [35, 36]