Interaction between the PapI protein and the alpha subunit of Escherichia coli RNA polymerase
(English)Manuscript (preprint) (Other academic)
Background: Uropathogenic Escherichia coli (UPEC) expressing P fimbriae (also denoted Pap or P pili) have the ability to adhere in a specific manner to uroepithelial cells in the cause of urinary tract infections. P fimbriae expression is subject to an intricate regulatory mechanism playing an important role in pathogenesis, allowing bacteria to sense its environment and express fimbriae when needed, and turn off the expression when it may be unnecessary or detrimental to the bacteria. The expression of P fimbriae in the uropathogenic E. coli depends on transcription of the major pap operon in a gene cluster that consists of the polycistronic papB operon and the divergently orientated monocistronic papI operon. The transcription of pap is positively controlled by the local transcription factors PapI (8 kDa) and PapB (12 kDa) in concert with the global regulators leucine-responsive regulatory protein (Lrp) and the cAMP receptor protein (CRP). DNA adenine methylase (Dam) activity is also required for pap transcription. PapI is known to interact with Lrp and its role in relation to the transcriptional activation of pap is thought to be indirect without contact with the RNA polymerase. The CRP-cAMP complex is known to activate the expression of pap via direct contact with the alpha (α) subunit of E. coli RNA polymerase. Methodology/Principal findings: Here, we show that an excess of α protein inhibits the transcription of pap as revealed by using a collection of strains which carry plasmids expressing α subunits with different point mutations in the α subunit of E. coli RNA polymerase. The inhibition was partially restored by the introduction of a papI clone expressing higher level of PapI. Experiments with purified proteins verified that PapI physically interacts with the α subunit of E. coli RNA polymerase in vitro. Conclusion/Significance: Our findings indicate that the PapI protein may interact directly with the RNA polymerase complex and that such interactions need to be considered in its role as a transcription factor in the activation of pap transcription.
Escherichia coli, PapI, alpha subunit, RNAP
Microbiology in the medical area
Research subject Molecular Biology
IdentifiersURN: urn:nbn:se:umu:diva-27738OAI: oai:DiVA.org:umu-27738DiVA: diva2:277441