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A phage satellite manipulates the viral DNA packaging motor to inhibit phage and promote satellite spread

Caroline M Boyd1, Kimberley D Seed1

  • 1Plant and Microbial Biology, University of California - Berkeley, Berkeley, CA 94720, USA.

Nucleic Acids Research
|August 16, 2024
PubMed

Insights

Phage satellite PLE inhibits Vibrio cholerae phage ICP1 packaging by targeting its terminase enzyme. PLE uses specific factors and mimicry to package its own genome, representing a novel satellite inhibition strategy.

Area of Science:

  • Microbiology
  • Virology
  • Molecular Biology

Background:

  • Bacteriophages like ICP1 are crucial in controlling bacterial populations, such as Vibrio cholerae.
  • Phage satellites (PLEs) are genetic elements that depend on helper phages, like ICP1, for replication and spread.
  • PLEs interfere with ICP1's lifecycle, but the mechanisms of inhibiting ICP1 genome packaging were unknown.

Purpose of the Study:

  • To identify and characterize the mechanism by which PLE inhibits ICP1 genome packaging.
  • To understand how PLE ensures its own genome packaging in the presence of ICP1.
  • To elucidate the broader implications of satellite-ICP1 interactions in phage biology.

Main Methods:

  • Biochemical assays to study protein-protein interactions between PLE and ICP1 components.
  • In vitro packaging assays to assess the effect of PLE factors on ICP1 genome packaging.
  • Analysis of PLE and ICP1 sequences for potential packaging signals and mimicry.

Main Results:

  • PLE encodes a protein, Gpi, that inhibits ICP1 genome packaging by binding to ICP1's large terminase (TerL).
  • PLE utilizes packaging specifiers (GpsA and GpsB) to overcome Gpi's inhibition and package its own genome.
  • PLE employs mimicry of ICP1's pac site as a backup strategy for genome packaging, dependent on other inhibitory mechanisms.

Conclusions:

  • Gpi is the first identified satellite-encoded inhibitor of phage TerL, revealing a novel mechanism of phage-satellite antagonism.
  • PLE exhibits a multi-pronged strategy to inhibit helper phage ICP1 and ensure its own propagation.
  • This study provides mechanistic insights into the complex interactions between phages and their satellites, highlighting PLE as a highly effective inhibitor.

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