Analysis of the Zika and Japanese Encephalitis Virus NS5 Interactomes

Mosquito-borne
flaviviruses, including dengue virus (DENV), Japanese
encephalitis virus (JEV), and Zika virus (ZIKV), are major human pathogens.
Among the flaviviral proteins, the nonstructural protein 5 (NS5) is
the largest, most conserved, and major enzymatic component of the
viral replication complex. Disruption of the common key NS5-host protein–protein
interactions critical for viral replication could aid in the development
of broad-spectrum antiflaviviral therapeutics. Hundreds of NS5 interactors
have been identified, but these are mostly DENV-NS5 interactors. To
this end, we sought to investigate the JEV- and ZIKV-NS5 interactomes
using EGFP immunoprecipitation with label-free quantitative mass spectrometry
analysis. We report here a total of 137 NS5 interactors with a significant
enrichment of spliceosomal and spliceosomal-associated proteins. The
transcription complex Paf1C and phosphatase 6 were identified as common
NS5-associated complexes. PAF1 was shown to play opposite roles in
JEV and ZIKV infections. Additionally, we validated several NS5 targets
and proposed their possible roles in infection. These include lipid-shuttling
proteins OSBPL9 and OSBPL11, component of RNAP3 transcription factor
TFIIIC, minichromosome maintenance, and cochaperone PAQosome. Mining
this data set, our study expands the current interaction landscape
of NS5 and uncovers several NS5 targets that are new to flavivirus
biology.