Involvement of ribonuclease III in the enhancement of expression of the speF-potE operon encoding inducible ornithine decarboxylase and polyamine transport protein.

Since the speF-potE operon (pPT71 clone) encoding inducible ornithine decarboxylase (iODC) and polyamine transport potE protein is inducible at acidic pH, a gene encoding a protein involved in the enhancement of expression of the operon was searched for. Using the fused gene containing the upstream sequence of the speF-potE operon and the open reading frame of beta-galactosidase as a reporter gene, a clone (pPTS23) which causes the increase of beta-galactosidase activity at acidic pH was isolated. The clone also increased iODC activity at acidic pH and was identified as a gene encoding RNase III. This is the first example that RNase III increases the translational efficiency of mRNA derived from Escherichia coli gene by cutting the 5'-untranslated region of mRNA.