Negative Regulation of IS 2 Transposition by the Cyclic AMP (cAMP)-cAMP Receptor Protein Complex

Abstract

ABSTRACT Three sequences similar to that of the consensus binding sequence of the cyclic AMP (cAMP)-cAMP receptor protein (CRP) complex were found in the major IS 2 promoter region. Experiments were performed to determine whether the cAMP-CRP complex plays a role in the regulation of IS 2 transposition. In the gel retardation assay, the cAMP-CRP complex was found to be able to bind the major IS 2 promoter. A DNA footprinting assay confirmed that the cAMP-CRP complex binds to the sequences mentioned above. With an IS 2 promoter-luciferase gene fusion construct, the cAMP-CRP complex was shown to inhibit transcription from the major IS 2 promoter. IS 2 was found to transpose at a frequency approximately 200-fold higher in an Escherichia coli host defective for CRP or adenyl cyclase than in a wild-type host. These results suggest that the cAMP-CRP complex is a negative regulator of IS 2 transposition.