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Special Issue “APOBECs and Virus Restriction”
Article

The Repressor C Protein, Pf4r, Controls Superinfection of Pseudomonas aeruginosa PAO1 by the Pf4 Filamentous Phage and Regulates Host Gene Expression

1
Singapore Centre for Environmental Life Sciences Engineering, Singapore 637551, Singapore
2
The School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore
3
Structural Biology Facility, Mark Wainwright Analytical Centre, The University of New South Wales, Sydney, NSW 2052, Australia
4
The iThree Institute, The University of Technology Sydney, Sydney, NSW 2007, Australia
*
Author to whom correspondence should be addressed.
Academic Editor: Dann Turner
Viruses 2021, 13(8), 1614; https://doi.org/10.3390/v13081614
Received: 22 July 2021 / Revised: 9 August 2021 / Accepted: 13 August 2021 / Published: 15 August 2021
(This article belongs to the Section Bacterial Viruses)
It has been shown that the filamentous phage, Pf4, plays an important role in biofilm development, stress tolerance, genetic variant formation and virulence in Pseudomonas aeruginosa PAO1. These behaviours are linked to the appearance of superinfective phage variants. Here, we have investigated the molecular mechanism of superinfection as well as how the Pf4 phage can control host gene expression to modulate host behaviours. Pf4 exists as a prophage in PAO1 and encodes a homologue of the P2 phage repressor C and was recently named Pf4r. Through a combination of molecular techniques, ChIPseq and transcriptomic analyses, we show a critical site in repressor C (Pf4r) where a mutation in the site, 788799A>G (Ser4Pro), causes Pf4r to lose its function as the immunity factor against reinfection by Pf4. X-ray crystal structure analysis shows that Pf4r forms symmetric homo-dimers homologous to the E.coli bacteriophage P2 RepC protein. A mutation, Pf4r*, associated with the superinfective Pf4r variant, found at the dimer interface, suggests dimer formation may be disrupted, which derepresses phage replication. This is supported by multi-angle light scattering (MALS) analysis, where the Pf4r* protein only forms monomers. The loss of dimerisation also explains the loss of Pf4r’s immunity function. Phenotypic assays showed that Pf4r increased LasB activity and was also associated with a slight increase in the percentage of morphotypic variants. ChIPseq and transcriptomic analyses suggest that Pf4r also likely functions as a transcriptional regulator for other host genes. Collectively, these data suggest the mechanism by which filamentous phages play such an important role in P. aeruginosa biofilm development. View Full-Text
Keywords: bacteriophage; gene regulation; biofilm bacteriophage; gene regulation; biofilm
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MDPI and ACS Style

Ismail, M.H.; Michie, K.A.; Goh, Y.F.; Noorian, P.; Kjelleberg, S.; Duggin, I.G.; McDougald, D.; Rice, S.A. The Repressor C Protein, Pf4r, Controls Superinfection of Pseudomonas aeruginosa PAO1 by the Pf4 Filamentous Phage and Regulates Host Gene Expression. Viruses 2021, 13, 1614. https://doi.org/10.3390/v13081614

AMA Style

Ismail MH, Michie KA, Goh YF, Noorian P, Kjelleberg S, Duggin IG, McDougald D, Rice SA. The Repressor C Protein, Pf4r, Controls Superinfection of Pseudomonas aeruginosa PAO1 by the Pf4 Filamentous Phage and Regulates Host Gene Expression. Viruses. 2021; 13(8):1614. https://doi.org/10.3390/v13081614

Chicago/Turabian Style

Ismail, Muhammad H., Katharine A. Michie, Yu F. Goh, Parisa Noorian, Staffan Kjelleberg, Iain G. Duggin, Diane McDougald, and Scott A. Rice. 2021. "The Repressor C Protein, Pf4r, Controls Superinfection of Pseudomonas aeruginosa PAO1 by the Pf4 Filamentous Phage and Regulates Host Gene Expression" Viruses 13, no. 8: 1614. https://doi.org/10.3390/v13081614

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