Regulation of clpQ+Y+ (hslV+U+) Gene Expression in Escherichia coli

Abstract

The Escherichia coli ClpYQ (HslUV) complex is an ATP-dependent protease, and the clpQ + Y + (hslV + U +) ope-ron encodes two heat shock proteins, ClpQ and ClpY, respectively. The transcriptional (op) or translational (pr) clpQ + ::lacZ fusion gene was constructed, with the clpQ + Y + promoter fused to a lacZ reporter gene. The clpQ + ::lacZ (op or pr) fusion gene was each crossed into lambda phage. The clpQ + ::lacZ + (op), a transcriptional fusion gene, was used to form lysogens in the wild-type, rpoH or/and rpoS mutants. Upon shifting the temperature up from 30 o C to 42 o C, the wild-type clpQ + ::lacZ + (op) demonstrates an increased-galactosidase (Gal) activity. However, the Gal activity of clpQ + ::lacZ + (op) was decreased in the rpoH and rpoH rpoS mutants but not in the rpoS mutant. The levels of clpQ + ::lacZ + mRNA transcripts correlated well to their Gal activity. Similarly, the expression of the clpQ + ::lacZ + gene fusion was nearly identical to the clpQ + Y + transcript under the in vivo condition. The clpQ m1 ::lacZ + , containing a point mutation in the-10 promoter region for RpoH binding, showed decreased Gal activity, independent of activation by RpoH. We conclude that RpoH itself regulates clpQ + Y + gene expression. In addition, the clpQ + Y + message carries a conserved 71 bp at the 5' untranslated region (5'UTR) that is predicted to form the stem-loop structure by analysis of its RNA secondary structure. The clpQ m2 40::lacZ + , with a 40 bp deletion in the 5'UTR, showed a decreased Gal activity. In addition , from our results, it is suggested that this stem-loop structure is necessary for the stability of the clpQ + Y + message.