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J. Bacteriol., Jul 1995, 3781-3787, Vol 177, No. 13
JA Fyfe, CS Carrick and JK Davies
Type 4 pili are essential for virulence in Neisseria gonorrhoeae. The
gonococcal pilin subunit is encoded by pilE, upstream of which three
putative promoter sequences (P1, P2, and P3) have been identified. P1 and
P2 are sigma 70-like promoters and are functional when a PpiE::cat
transcriptional fusion is expressed in Escherichia coli DH5 alpha. P3 is
sigma 54 dependent and overlaps the P1 sequence. Site-directed mutagenesis
of the pilE promoters followed by transcriptional analysis in E. coli
indicated that in the absence of an appropriate activator protein, binding
of RNA polymerase-sigma 54 to P3 inhibits transcription from P1 on the
order of 30-fold. Transcription from P3 was undetectable in E. coli.
However, PilR-dependent, P3-associated expression was detected in
Pseudomonas aeruginosa PAK containing a PpilE::cat fusion, with P3 the only
intact promoter. A similar analysis was performed on gonococcal reporter
strains containing wild-type and mutated PpilE::cat cassettes recombined
into the chromosome. In such piliated gonococcal recombinants cultured in
vitro, P1 was responsible for cat expression and almost certainly for
transcription of pilE. Transcription from P2 and P3 was not detectable
under these conditions. Inhibition of transcription from P1 by sigma 54
binding to P3 was not apparent in N. gonorrhoeae MS11-A, suggesting that
sigma 54 was either absent or unable to bind to P3 in these cells.
Copyright © 1995, American Society for Microbiology
The pilE gene of Neisseria gonorrhoeae MS11 is transcribed from a sigma 70 promoter during growth in vitro
Department of Microbiology, Monash University, Clayton, Victoria, Australia.
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