Identification, characterization, and variable expression of a naturally occurring inhibitor protein of IS1106 transposase in clinical isolates of Neisseria meningitidis

Transposition plays a role in the epidemiology and pathogenesis of Neisseri a meningitidis. Insertion sequences are involved in reversible capsulation and insertional inactivation of virulence genes encoding outer membrane pro teins. In this study, we have investigated and identified one way in which transposon IS1106 controls its own activity. We have characterized a natura lly occurring protein (Tip) that inhibits the transposase. The inhibitor pr otein is a truncated version of the IS1106 transposase lacking the NH2-term inal DNA binding sequence, and it regulates transposition by competing with the transposase for binding to the outside ends of IS1106, as shown by gel shift and in vitro transposition assays. IS1106Tip mRNA is variably expres sed among serogroup B meningococcal clinical isolates, and it is absent in most collection strains belonging to hypervirulent lineages.