CspE inhibits the expression of cspA in vitro by increasing pause recognition for RNA polymerase at the cspA "cold box" [10]. cspA expression was increased in a uvrY mutant strain and reduced when uvrY was overexpressed [11]. CspA belongs to the cold shock family of proteins and was shown to be homologous to eukaryotic Y-box transcription factors [12, 13]. The transcription factors of this family recognize a CCAAT sequence in the regulatory region of the genes regulated [2, 3]. The crystal structure of CspA has been determined by X-ray crystallography to a resolution of 2.0 Å [14]; also, the structure of CspA has been determined by NMR spectroscopy [15, 16]. On other hand, Jiang et al. in 1997 demonstrated that CspA acts as an RNA chaperone that prevents secondary structure formation of RNA at low temperatures [8, 17]. cspA is not only expressed at low temperatures but also at 37°C during nutritional up-shift conditions, until the cells start dividing [18]. cspA mRNA is very unstable at 37°C and rapidly disappears as the cell density and RNase activity increase [19, 20]. The lability of cspA mRNA at high temperatures is mediated by cleavage toward its 3' end; this cleavage is partially dependent on RNase E [21]. Thus, cspA expression levels change in response to temperature fluctuations [22]. The long 5' untranslated region of cspA mRNA contains a feature within the first 25 bases that is responsible for derepression of cspA expression and inhibition of synthesis of cellular proteins other than cold shock proteins following cold shock [23]. cspA was also shown to be induced by addition of chloramphenicol and was induced even in the absence of protein synthesis [24, 25]. By making use of microarrays analysis, Constantinidou et al. [26] concluded that FNR represses cspA gene expression, but it is not known which of the two promoters (cspAp1, cspAp2) is affected. The authors also identified a putative FNR-binding site upstream of the gene, but the sequence was not reported. Fis and HNS activate and repress cspA transcription, respectively, and their effects cancel each other when they act together, resulting in basal activity of cspA [18].