The suhB gene encodes a 29-kDa protein that possesses inositol monophosphate activity and its mutations suppress several temperature-sensitive mutations in Escherichia coli. We found that the suhB gene is autoregulated; suhB- mutant strains oversynthesized the suhB mRNA and suhB-lacZ gene/operon fusion products. Since the half-life of the suhB transcript in the suhB mutant was much greater than the half-life in the wildtype strain, the suhB protein is implicated in the control of gene expression by modulating mRNA turnover.