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Separating Functions of the Phage-Encoded Quorum-Sensing-Activated Antirepressor Qtip
Justin E Silpe1, Andrew A Bridges2, Xiuliang Huang2
1Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
Cell Host & Microbe
|February 27, 2020
Summary
Bacterial phages use quorum sensing to control their life cycle. Vibriophage VP882’s Qtip protein inhibits the host repressor, triggering cell lysis and demonstrating separable localization and interference functions.
Area of Science:
- Microbiology
- Virology
- Molecular Biology
Background:
- Quorum sensing allows bacteria to communicate cell density and coordinate gene expression.
- Bacteriophages can utilize host quorum sensing to influence their replication strategy (lysis or lysogeny).
- Vibriophage VP882 employs quorum sensing, producing Qtip to mediate the lysis-lysogeny decision.
Purpose of the Study:
- To investigate the molecular mechanism by which Qtip interferes with the Vibriophage VP882 repressor (cIVP882).
- To determine if Qtip's functions of repressor inhibition and cellular localization are linked.
- To compare Qtip's mechanism to other known phage antirepressors.
Main Methods:
- Protein interaction studies to identify the binding site of Qtip on cIVP882.
- Biochemical assays to assess the impact of Qtip on cIVP882 DNA binding and autoproteolysis.
- Alanine-scanning mutagenesis of Qtip to map functional domains.
- Microscopy to observe the cellular localization of Qtip and cIVP882.
Main Results:
- Qtip binds to the N-terminus of cIVP882, inhibiting its DNA binding and autoproteolysis.
- Qtip induces the sequestration and polar localization of cIVP882 within the host cell.
- Qtip exhibits polar localization independently of cIVP882.
- Mutagenesis studies reveal that Qtip's localization and repressor interference activities are separable.
Conclusions:
- Qtip is a novel phage antirepressor that inhibits cIVP882 activity and induces its polar localization.
- The polar localization function of Qtip is distinct from its repressor inhibition function.
- Qtip's unique mechanism of polar localization differentiates it from canonical phage antirepressors.
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