7t5h
Structure of rabies virus phosphoprotein C-terminal domain, wild type
Structural highlights
FunctionPHOSP_RABVN Non catalytic polymerase cofactor and regulatory protein that plays a role in viral transcription and replication. Stabilizes the RNA polymerase L to the N-RNA template and binds the soluble protein N, preventing it from encapsidating non-genomic RNA. Also inhibits host IFN-alpha and IFN-beta signaling by binding and retaining phosphorylated STAT1 in the cytoplasm or by inhibiting the DNA binding of STAT1 in the nucleus. Might be involved, through interaction with host dynein, in intracellular microtubule-dependent virus transport of incoming virus from the synapse toward the cell body (By similarity). Publication Abstract from PubMedThe rabies virus (RABV) phosphoprotein (P protein) is expressed as several isoforms, which differ in nucleocytoplasmic localization and microtubule (MT) association, mediated by several sequences, including nuclear localization (NLS) and export (NES) sequences. This appears to underpin a functional diversity enabling multiple functions in viral replication and modulation of host biology. Mechanisms regulating trafficking are poorly defined, but phosphorylation by protein kinase C (PKC) in the P protein C-terminal domain (PCTD) regulates nuclear trafficking, mediated by PCTD-localized NLS/NES sequences, indicating that phosphorylation contributes to functional diversity. The molecular mechanism underlying the effects of PKC, and potential roles in regulating other host-cell interactions are unresolved. Here, we assess effects of phosphorylation on the P3 isoform, which differs from longer isoforms through an ability to localize to the nucleus and associate with MTs, which are associated with antagonism of interferon (IFN) signaling. We find that phosphomimetic mutation of the PKC site S210 inhibits nuclear accumulation and MT association/bundling. Structural analysis indicated that phosphomimetic mutation induces no significant structural change to the NLS/NES but results in the side chain of N226 switching its interactions from E228, within the NES, to E210. Intriguingly, N226 is the sole substituted residue between the PCTD of the pathogenic IFN-resistant RABV strain Nishigahara and a derivative attenuated IFN-sensitive strain Ni-CE, inhibiting P3 nuclear localization and MT association. Thus, S210 phosphorylation appears to impact on N226/E228 to regulate P protein localization, with N226 mutation in Ni-CE mimicking a constitutively phosphorylated state resulting in IFN sensitivity and attenuation. IMPORTANCE Rabies virus P protein is a multifunctional protein with critical roles in replication and manipulation of host-cell processes, including subversion of immunity. This functional diversity involves interactions of several P protein isoforms with the cell nucleus and microtubules. Previous studies showed that phosphorylation of the P protein C-terminal domain (PCTD) at S210, near nuclear trafficking sequences, regulates nucleocytoplasmic localization, indicating key roles in functional diversity. The molecular mechanisms of this regulation have remained unknown. Here, we show that phosphomimetic mutation of S210 regulates nuclear localization and MT association. This regulation does not appear to result from disrupted PCTD structure, but rather from a switch of specific side chain interactions of N226. Intriguingly, N226 was previously implicated in P protein nuclear localization/MT association, immune evasion, and RABV pathogenesis, through undefined mechanisms. Our data indicate that the S210-N226 interface is a key regulator of virus-host interactions, which is significant for pathogenesis. Molecular Basis of Functional Effects of Phosphorylation of the C-Terminal Domain of the Rabies Virus P Protein.,Zhan J, Watts E, Brice AM, Metcalfe RD, Rozario AM, Sethi A, Yan F, Bell TDM, Griffin MDW, Moseley GW, Gooley PR J Virol. 2022 Apr 11:e0011122. doi: 10.1128/jvi.00111-22. PMID:35404083[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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