Regulation of Salmonella pathogenicity island I through the hilD mRNA 3' untranslated region

Abdulla, Sabrina Zahir

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https://hdl.handle.net/2142/120483 Copy

Description

Title

Regulation of Salmonella pathogenicity island I through the hilD mRNA 3' untranslated region

Author(s)

Abdulla, Sabrina Zahir

Issue Date

2023-01-17

Director of Research (if dissertation) or Advisor (if thesis)

Vanderpool, Carin K

Doctoral Committee Chair(s)

Vanderpool, Carin K

Committee Member(s)

• Slauch, James M
• Metcalf, William W
• Kuzminov, Andrei

Department of Study

Microbiology

Discipline

Microbiology

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Salmonella, pathogenicity, SPI-1, sRNAs

Abstract

Salmonella enterica serovar Typhimurium is an enteric pathogen associated with food-borne disease. Salmonella invades the intestinal epithelium using a type three secretion system encoded on Salmonella pathogenicity Island 1 (SPI-1). SPI-1 genes are tightly regulated by a complex feed-forward loop to ensure proper spatial and temporal expression. Most regulatory input is integrated at HilD, through control of hilD mRNA translation or HilD protein activity. The hilD mRNA possesses a 310-nucleotide 3′ untranslated region (UTR) that influences HilD and SPI-1 expression, and this regulation is dependent on Hfq and RNase E, cofactors known to mediate small RNA (sRNA) activities. Thus, we hypothesized that the hilD mRNA 3′ UTR is a target for sRNAs. Here we show that the sRNAs, SdsR and Spot 42, regulate SPI-1 by targeting different regions of the hilD mRNA 3′ UTR. Regulatory activities of these sRNAs depend on Hfq and RNase E, in agreement with previous roles found for both at the hilD 3′ UTR. Salmonella mutants lacking SdsR and Spot 42 have decreased virulence in a mouse model of infection. Collectively, this work suggests that these sRNAs targeting the hilD mRNA 3′ UTR increase hilD mRNA levels by interfering with RNase E-dependent mRNA degradation and that this regulatory effect is required for Salmonella invasiveness. Further, we identify a role for Rho and NusG at the hilD mRNA 3′UTR. Previous work has identified that Gre factors are essential to allow for proper hilD expression. Here, we identify that Gre factors are only required when Rho is functional, implicating a mechanism where Gre factors helps bypass premature termination by Rho during SPI-1 permissive conditions. In addition, we find that there is interplay between Rho, RNase E and SdsR, providing new insight into the mechanism by which the hilD mRNA 3′ UTR functions as a regulatory module. Our work provides novel insights into mechanisms of sRNA regulation at bacterial mRNA 3′ UTRs, and adds to our knowledge of post-transcriptional regulation and transcription termination as a means of regulating the SPI-1 complex feed-forward loop.

Graduation Semester

2023-05

Type of Resource

Thesis

Copyright and License Information

Copyright 2023 Sabrina Abdulla

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