Transcriptional activation of a pap pilus virulence operon from uropathogenic Escherichia coli.

Abstract

A gene cluster mediating production of pili in uropathogenic Escherichia coli was analysed with respect to regulation of pili synthesis. Two cistrons, papB and papI, were localized upstream of the major pilus subunit gene, papA. The papI‐papB‐papA region was characterized by nucleotide sequencing and by transcriptional analysis. The papA gene was primarily represented by an 800 nucleotide long transcript but was also co‐transcribed with papB as a less abundant 1300 nucleotide long mRNA. Both transcripts presumably terminated at the same site downstream of the papA coding sequence. The weakly expressed papI gene was transcribed in the opposite direction to that of papB and papA. Studies with lacZ operon fusions showed that the papB gene encoded a trans‐active effector required for papA transcription. Similarly, the papI gene stimulated papB transcription in trans. Furthermore, full expression of papA was cis dependent upon the papI‐papB region. Transcription of the papB gene was shown to be dependent upon cAMP and its receptor protein. A binding site for the cAMP‐CRP complex was postulated in the DNA sequence upstream of the papB promoter.

Self-perpetuating epigenetic pili switches in bacteria

“…Early studies by Uhlin's laboratory established that PapB plays an essential role in activation of pap transcription (14). There is a least one high affinity PapB binding site, located between the CAP binding site and the papI promoter in each pap operon that has been studied ( Fig.…”

“…CAP plays important roles in activation at the papBA and papI promoters (14)(15)(16)25). Binding of CAP to a single site located at Ϫ215.5 bp from the papBA start and Ϫ115.5 bp from the papI start is essential for activation of both papBA and papI transcription.…”

Solution Structure of Escherichia coli PapI, a Key Regulator of the Pap Pili Phase Variation

“…3,4,5 This modulation in the DNA-binding activity of Lrp plays a central role in the pap phase variation, and, as evidenced by early genetic studies, it depends on the local regulator PapI. 6,7,8 The entire mechanism of pap regulation involves ¥corresponding author, Email: dahlquist@chem.ucsb.edu, Phone: 805-893-5326, Fax: 805-893-4120. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication.…”

Evidence for a methylation-blocking factor (mbf) locus involved in pap pilus expression and phase variation in Escherichia coli

“…Studies carried out with a single-copy pap-lac operon fusion in E. coli K-12 indicate that alternation between the phase-on and phase-off states occurs at the level ofpap pilin transcription and is affected by both incubation temperature (13,32) and the carbon source used for growth of the bacteria (3,7). Our recent studies indicate that pap pilin phase variation occurs through a novel mechanism involving the differential methylation of two DNA GATC sites (GATC1028 and GATC1130) near the papBA pilin promoter by deoxyadenosine methylase (Dam) (7).…”

“…Alternatively, binding of a protein to a DNA site that overlapped a GATC sequence could inhibit Dam methylation of that site. Baga et al (3) and Forsman et al (11) have found that two pap genes, papI and papB, are involved in the regulation of pap pilin transcription. In this article, we provide evidence suggesting that papI plays a role in the inhibition of methylation at the GATC1028 site.…”