Henipaviruses and lyssaviruses target nucleolar treacle protein and regulate ribosomal RNA synthesis

Abstract

The nucleolus is a common target of viruses and viral proteins, but for many viruses the functional outcomes and significance of this targeting remains unresolved. Recently, the first intranucleolar function of a protein of a cytoplasmically‐replicating negative‐sense RNA virus (NSV) was identified, with the finding that the matrix (M) protein of Hendra virus (HeV) (genus Henipavirus, family Paramyxoviridae) interacts with Treacle protein within nucleolar subcompartments and mimics a cellular mechanism of the nucleolar DNA‐damage response (DDR) to suppress ribosomal RNA (rRNA) synthesis. Whether other viruses utilise this mechanism has not been examined. We report that sub‐nucleolar Treacle targeting and modulation is conserved between M proteins of multiple Henipaviruses, including Nipah virus and other potentially zoonotic viruses. Furthermore, this function is also evident for P3 protein of rabies virus, the prototype virus of a different RNA virus family (Rhabdoviridae), with Treacle depletion in cells also found to impact virus production. These data indicate that unrelated proteins of viruses from different families have independently developed nucleolar/Treacle targeting function, but that modulation of Treacle has distinct effects on infection. Thus, subversion of Treacle may be an important process in infection by diverse NSVs, and so could provide novel targets for antiviral approaches with broad specificity.

Definition of mechanisms of viral protein multifunctionality reveals key roles of ‘conformer diversity’ and RNA interaction in forming host interfaces

“…Of the mutants in the CTD, nuclear accumulation of P3-KRm was reduced compared with wt P3 and enhanced by LMB, and nucleolar localization of P3-KRm in LMB-treated and untreated cells remained similar to that of GFP alone, as previously reported 21 (Figure 1G). The KRm mutations inhibit interaction of the C-NLS with importins and enhance nuclear export that involves a Cterminal NES (C-NES) 14,19 .. P3-K282N and P3-K285N were strongly excluded from the nucleus, but accumulated into the nucleus following LMB treatment and could enter nucleoli, albeit to a significantly reduced level (p < 0.0001) compared with wt P3.…”

“…P3 interacts with PML protein-containing NBs 22 , nucleoli 20 and MT bundles 16 , which would conventionally be considered to relate to protein-protein associations, consistent with reported interactions of P protein with PML protein, nucleolin and Treacle [20][21][22] . However, the lack of apparent interaction of P1 with such structures (Figure 1 and refs.…”

“…62 of these proteins associate with one or more MLOs, including nucleoli, NBs (paraspeckles, nuclear speckles, Cajal bodies), stress granules (SGs) and P-bodies (Figure 4A). 45 of the proteins localize to nucleoli, including nucleophosmin (NPM1), and RNA helicases DDX5 and DDX17, which are linked to pro-or antiviral function [49][50][51] and treacle, a validated P3 interactor 21 . NCL, another validated P3 interactor important to RABV infection 20 , was identified in all assays, but was excluded due to identification in IP/MS of GFP alone.…”

“…Previous reports have indicated that truncation to produce P3 (residues 53-297) results in a heterogenous phenotype through interactions and functions that are not evident for P1, including MT association/bundling 16,17 , nuclear accumulation 14,18,19 , nucleolar targeting 20,21 and association with nuclear bodies 22 . Truncation deletes residues 1-52 (Figure 1A), removing the N-NES and resulting in nuclear localization 14 .…”

A TRAFFIC themed series ‐ Host membrane trafficking subversion by pathogens

“…Stephen Rawlinson, Gregory Moseley and colleagues identify a property shared by different negative sense RNA viruses, in the ability to interact with Treacle, a protein involved in the nucleolar DNA‐Damage‐Response. By subverting Treacle function these viruses are thus able to impact on and repress ribosomal RNA synthesis 6 …”