INTEGRATION HOST FACTOR IS A TRANSCRIPTIONAL COFACTOR OF PILE IN NEISSERIA-GONORRHOEAE

Integration host factor (IHF) is a small, heterodimeric DNA-binding pr otein with pleiotropic function. IHF was purified to apparent homogene ity from Neisseria gonorrhoeae. Gel-retardation assays demonstrated bi nding of IHF to the pilE promoter region. The IHF-binding site was ide ntified by DNase I protection assays and mapped proximal to three prev iously defined pilE promoters. Removal of the putative IHF-binding dom ain from pilE promoter DNA negated retardation of the DNA fragment whe n assessed by gel-shift analysis. Kleinschmidt electron microscopy sho wed pronounced kinking of pilE promoter DNA following incubation with IHF. Isogenic N. gonorrhoeae strains were constructed that contained e ither a wild-type pilE locus or a deleted pilE locus where the IHF-bin ding domain was removed. Primer-extension analysis and Northern blotti ng of total gonococcal RNA showed that in the absence of IHF binding a t the pilE promoter, transcription was reduced 10-fold. Together, thes e data indicate that IHF is a transcriptional co-activator of pilE.