Definition of the immune evasion-replication interface of rabies virus P protein

PLoS Pathog. 2021 Jul 8;17(7):e1009729. doi: 10.1371/journal.ppat.1009729. eCollection 2021 Jul.

Abstract

Rabies virus phosphoprotein (P protein) is a multifunctional protein that plays key roles in replication as the polymerase cofactor that binds to the complex of viral genomic RNA and the nucleoprotein (N protein), and in evading the innate immune response by binding to STAT transcription factors. These interactions are mediated by the C-terminal domain of P (PCTD). The colocation of these binding sites in the small globular PCTD raises the question of how these interactions underlying replication and immune evasion, central to viral infection, are coordinated and, potentially, coregulated. While direct data on the binding interface of the PCTD for STAT1 is available, the lack of direct structural data on the sites that bind N protein limits our understanding of this interaction hub. The PCTD was proposed to bind via two sites to a flexible loop of N protein (Npep) that is not visible in crystal structures, but no direct analysis of this interaction has been reported. Here we use Nuclear Magnetic Resonance, and molecular modelling to show N protein residues, Leu381, Asp383, Asp384 and phosphor-Ser389, are likely to bind to a 'positive patch' of the PCTD formed by Lys211, Lys214 and Arg260. Furthermore, in contrast to previous predictions we identify a single site of interaction on the PCTD by this Npep. Intriguingly, this site is proximal to the defined STAT1 binding site that includes Ile201 to Phe209. However, cell-based assays indicate that STAT1 and N protein do not compete for P protein. Thus, it appears that interactions critical to replication and immune evasion can occur simultaneously with the same molecules of P protein so that the binding of P protein to activated STAT1 can potentially occur without interrupting interactions involved in replication. These data suggest that replication complexes might be directly involved in STAT1 antagonism.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • COS Cells
  • Chlorocebus aethiops
  • HEK293 Cells
  • Humans
  • Immune Evasion / physiology*
  • Molecular Chaperones / metabolism*
  • Nucleocapsid Proteins / metabolism
  • Rabies / metabolism
  • Rabies / virology*
  • Rabies virus / metabolism*
  • STAT1 Transcription Factor / metabolism
  • Viral Structural Proteins / metabolism*
  • Virus Replication / physiology*

Substances

  • Molecular Chaperones
  • Nucleocapsid Proteins
  • P phosphoprotein, Rabies virus
  • STAT1 Transcription Factor
  • Viral Structural Proteins
  • nucleocapsid protein, Rabies virus

Grants and funding

This research was supported by National Health & Medical Research Council Australia grants (https://www.nhmrc.gov.au/) 1125704 (G.W.M and P.R.G), 1079211, 1003244, 1160838 (G.W.M), 1174405 (D.B.A and T.B.N), Australian Research Council discovery project grant (https://www.arc.gov.au/) DP150102569 (G.W.M), Meigunyah Trust Grimwade Fellowship (G.W.M), Australian Government Research Training Program Scholarship (A.R.H) and Melbourne Research Scholarships (J.Z. and S.P.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.