Henipavirus V Protein Association with Polo-Like Kinase Reveals Functional Overlap with STAT1 Binding and Interferon Evasion

Abstract

Emerging viruses in the paramyxovirus genusThe genus Henipavirus within the family Paramyxoviridae was created in 2002 to accommodate the recently emerging and closely related Nipah and Hendra viruses (10,28,46,47). Nipah virus emerged in Peninsular Malaysia in 1998 as a result of human contact with infected swine, and recent outbreaks have been reported in Bangladesh and India between 2001 and 2005 (7, 17, 20, 27). Hendra virus emerged in Brisbane, Australia, in 1994 as a result of human contact with infected horses and last appeared in Queensland, Australia, in 2004 (3, 32). The viruses were responsible for zoonotic respiratory disease and severe acute encephalitis in humans and livestock and exhibit respiratory and neurological tropism (24). These human pathogens are set apart by their low homology to other paramyxoviruses, wide host range, and high level of virulence, which has limited investigations into the interaction of virally encoded Henipavirus proteins with their natural host and susceptible livestock. Furthermore, these viruses caused significant economic losses for the Malaysian swine industry (30), and their potential use in bioterrorist scenarios (23), due to a lack of therapeutic intervention, warrants further investigation.The cellular response to type I interferons (IFNs) (IFN-␣ and IFN-␤, collectively referred to as IFN) results in the establishment of a potent antiviral state in addition to regulating components of the adaptive immune response (21,22). This process is mediated by the signal transducer and activator of transcription (STAT) protein family. Following IFN exposure, STAT proteins translocate to the nucleus to directly regulate cellular gene transcription, creating a cellular antiviral state (1). Many viruses have evolved well-characterized adaptations to evade the IFN-induced antiviral responses of their hosts (15). The family Paramyxoviridae, comprised of enveloped negative-strand RNA viruses in several distinct genera, has developed unique molecular mechanisms of IFN signaling inhibition, several of which have been attributed to a virus-encoded protein derived from a polycistronic gene (10,18,19).As with other paramyxoviruses, the cotranscriptional insertion of nontemplated nucleotides generates alternative mRNAs from the Henipavirus P locus, encoding the P, V, and W proteins (45). A fourth protein, C, is generated by alternate translation initiation site selection from all these mRNAs and is unrelated to the other products. The P, V, and W proteins share 407 amino acids in their N termini but differ in their C termini as a result of alternate reading frames produced by the addition of nontemplated nucleotides at the "editing site" (Fig. 1A). The P protein contains an additional 301 amino acids to produce a 78-kDa polypeptide. The P protein is highly phosphorylated, albeit by unknown kinase(s) (43), and is an essential component of the RNA transcription and replication machinery (8). The V protein C-terminal domain (CTD) is 50 amino acids in length and encodes a zinc finger do...

Nipah Virus Sequesters Inactive STAT1 in the Nucleus via a P Gene-Encoded Mechanism

“…Notably, the PLK1-binding site overlaps the STAT1-binding site on P, V, and W, and mutations that disrupt the V-PLK1 interaction also disrupt the V-STAT1 interaction. However, the same mutations do not affect P replication function (30). It will be of interest to determine which of the mutations described above also affect the P or V interaction with PLK1.…”

“…Whether the cytoplasmic P protein functions identically to V remains to be determined. Finally, it has been demonstrated that NiV P, V, and W interact with pololike kinase 1 (PLK1), and this interaction results in V phosphorylation (30). Notably, the PLK1-binding site overlaps the STAT1-binding site on P, V, and W, and mutations that disrupt the V-PLK1 interaction also disrupt the V-STAT1 interaction.…”

STAT2 Is a Primary Target for Measles Virus V Protein-Mediated Alpha/Beta Interferon Signaling Inhibition

“…This STAT1 interaction is mediated by an amino terminal peptide requiring residues 110 through 130, a region noted for high sequence conservation among members of the Morbillivirus family (8), that is present in both the P and V proteins. It is interesting that Nipah virus and Hendra virus, distantly related paramyxoviruses of the Henipavirus genus, also bind to STAT1 with residues in the P/V common region, via amino acids 100 to 160 for the Nipah virus P, V, and W proteins (26,39,42). For measles virus, this region originates with tyrosine 110, a residue that has been implicated in control of IFN responses.…”

Henipavirus pathogenesis and antiviral approaches

“…The V and W proteins both localize in the cytoplasm and in the nucleus for the latter and have been shown to inhibit JAK/STAT signaling [58][59][60][61]. The ability to bind STAT relies on amino acids at positions 130 and 131, common to P, V and W [62]. W protein has a nuclear localization signal, which allows its entry into the nucleus where it can aggregate STAT1 and prevent its binding to the ISRE and consequently block IRF3 and IFN beta transcription [60].…”