AI Article Synopsis

  • Viruses compete for cellular resources, and some produce defense systems like PARIS, which consists of two proteins: AriA (an ATPase) and AriB (a nuclease).
  • The study reveals that AriA and AriB form a large immune complex, where AriA shapes a scaffold for AriB, enabling it to detect and respond to foreign proteins.
  • Phage T5 can evade this defense by using a tRNA variant that avoids cleavage by PARIS, illustrating a co-evolutionary struggle between viruses and host defenses.

Article Abstract

Viruses compete with each other for limited cellular resources, and some viruses deliver defense mechanisms that protect the host from competing genetic parasites. PARIS is a defense system, often encoded in viral genomes, that is composed of a 53 kDa ABC ATPase (AriA) and a 35 kDa TOPRIM nuclease (AriB). Here we show that AriA and AriB assemble into a 425 kDa supramolecular immune complex. We use cryo-EM to determine the structure of this complex which explains how six molecules of AriA assemble into a propeller-shaped scaffold that coordinates three subunits of AriB. ATP-dependent detection of foreign proteins triggers the release of AriB, which assembles into a homodimeric nuclease that blocks infection by cleaving the host tRNA. Phage T5 subverts PARIS immunity through expression of a tRNA variant that prevents PARIS-mediated cleavage, and thereby restores viral infection. Collectively, these data explain how AriA functions as an ATP-dependent sensor that detects viral proteins and activates the AriB toxin. PARIS is one of an emerging set of immune systems that form macromolecular complexes for the recognition of foreign proteins, rather than foreign nucleic acids.

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC10802454PMC
http://dx.doi.org/10.1101/2024.01.02.573894DOI Listing

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