title: The regulatory role of the IS1-encoded InsA protein in transposition.
abstract: We show here that the protein InsA, which is encoded by IS1 and binds specifically to the terminal inverted repeats of this insertion sequence, negatively regulates IS1 transposition activity. We demonstrate that it inhibits both IS1-mediated cointegrate formation and transposition of a synthetic IS1-based transposon ('omegon'; omega-on). These results also indicate that the omega-on which does not itself encode IS1 transposition functions can be complemented in trans, presumably by the copies of IS1 resident in the Escherichia coli chromosome. Using insA-lacZ gene fusions, we show that at least part of this effect can be explained by the ability of InsA to repress expression of IS1-encoded genes both in cis or in trans. The experiments involving omega-on transposition raise the possibility that InsA inhibits transposition directly by competition with the transposase for their cognate site within the ends of IS1.
authors.affiliation: Centre de Recherche de Biochimie et Génétique Cellulaires du CNRS, Toulouse, France.
authors.forename: D
authors.initials: D
authors.lastname: Zerbib
authors.forename: P
authors.initials: P
authors.lastname: Polard
authors.forename: J M
authors.initials: JM
authors.lastname: Escoubas
authors.forename: D
authors.initials: D
authors.lastname: Galas
authors.forename: M
authors.initials: M
authors.lastname: Chandler
mesh_terms: D001483:Base Sequence; D004251:DNA Transposable Elements; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D007763:Lac Operon; D008969:Molecular Sequence Data; D009713:Nucleotidyltransferases / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid; D012097:Repressor Proteins / Q000096:biosynthesis / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics*; D019895:Transposases
chemical_list: D004251:DNA Transposable Elements; D029968:Escherichia coli Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C064548:insA1 protein, E coli; D009713:Nucleotidyltransferases; D019895:Transposases