Tn7 transposition: a multigene process. Identification of a regulatory gene product.

Tn7 transposition is abolished by the deletion of a 2.2kb HindIII fragment from the central region of the transposon. Transposition is restored when the fragment is present in trans. When this fragment is present in trans with wild-type Tn7, transposition frequencies are stimulated 10-100-fold. The DNA sequence of this fragment has been determined and found to contain one long open reading frame coding for a protein of molecular weight 61 187. We have visualised this protein using a DNA-directed prokaryotic transcription-translation system. This gene may fill a regulatory role in the mechanism of Tn7 transposition. When present in trans the 2.2kb HindIII fragment alleviates a transcriptional block of promoter activity detected in Tn7.