An unusually long 5'UTR of ATP dependent cold shock DEAD-box RNA helicase gene csdA negatively regulates its own expression in Escherichia coli

Cold-shock DEAD-box protein A (CsdA) is an ATP dependant cold shock DEAD-box RNA helicase. It is a major cold shock protein needed for the cold adaptation in Escherichia coli. Although the CsdA has been studied at the protein level, further studies are necessary to understand its mechanisms of gene regulations. In this regard, we have constructed a promoter less vector with the ORF of a GFP reporter and found that the promoter of the csdA gene resides far upstream (more than 800 bases) of its coding region. Furthermore, our in vivo deletion experiment has confirmed the existence of this extraordinarily long 5UTR. Our results show that it represses its own expression. In addition, the short peptide encoding (26 aa) yrbN gene resides within this 5UTR as an operon with 8 overlapping nucleotides with the csdA coding region. Besides, we observed that the csdA gene expression may also occur along with immediate upstream (180 nucleotides) nlpI gene both at 37{degrees}C and 15{degrees}C and from the pnp gene (1173 nucleotides upstream) only during cold. In conclusion, csdA gene has operon feature like prokaryotes, in contrast, it also contains an extraordinarily long 5UTR, found in eukaryotes.