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A phage satellite tunes inducing phage gene expression using a domesticated endonuclease to balance inhibition and

Zoe Netter1, Caroline M Boyd1, Tania V Silvas1

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

Nucleic Acids Research
|April 6, 2021
PubMed

Insights

A bacterial virus satellite, PLE, uses a novel protein, CapR, to repress phage ICP1 gene transcription. This mechanism allows PLE to hijack phage processes for its own mobilization, revealing a unique bacterial defense strategy.

Area of Science:

  • Microbiology
  • Virology
  • Molecular Biology

Background:

  • Bacteria face constant predation from bacterial viruses (phages).
  • Mobile genetic elements (MGEs), like phage satellites, drive evolutionary arms races between bacteria and phages.
  • The Vibrio cholerae phage satellite PLE defends against the lytic phage ICP1.

Purpose of the Study:

  • To elucidate the mechanism by which PLE manipulates ICP1 gene transcription.
  • To investigate the role of the PLE-encoded protein CapR in repressing ICP1.
  • To understand the evolutionary origins and mobilization strategies of PLE.

Main Methods:

  • Described PLE-mediated transcriptional manipulation of ICP1 structural genes.
  • Identified and characterized the DNA binding protein CapR.
  • Utilized CRISPR interference (CRISPRi) for stringent repression studies.
  • Examined PLE transduction within modified ICP1-like particles.
  • Analyzed CapR homologs and ICP1-encoded homing endonucleases.

Main Results:

  • PLE encodes CapR, a novel DNA binding protein that represses ICP1's capsid morphogenesis operon.
  • CapR-mediated repression is sufficient for PLE's defense but does not halt the ICP1 lifecycle.
  • Stringent repression via CRISPRi restricts both ICP1 and PLE replication.
  • PLE is shown to transduce within modified ICP1-like particles.
  • ICP1-encoded homing endonucleases are identified as putative origins for the satellite-encoded repressor CapR.

Conclusions:

  • PLE employs molecular parasitism by transcriptionally inhibiting ICP1, enabling its own mobilization.
  • The CapR-ICP1 interaction highlights a sophisticated bacterial defense and phage counter-defense mechanism.
  • This study reveals the intricate balance in satellite-mediated phage inhibition and propagation.

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