GSE185829
FEAR antiviral response pathway is independent of interferons and countered by poxvirus proteins
The human facilitates chromatin transcription (FACT) complex is a chromatin remodeller composed of human suppressor of Ty 16 homologue (hSpt16) and structure-specific recognition protein-1 subunits that regulates cellular gene expression. Whether FACT regulates host responses to infection remained unclear. We identify a FACT-mediated, interferon-independent, antiviral pathway that restricts poxvirus replication. Cell culture and bioinformatics approaches suggest that early viral gene expression triggers nuclear accumulation of SUMOylated hSpt16 subunits required for the expression of E26 transformation-specific sequence-1 (ETS-1)-a transcription factor that activates virus restriction programs. However, biochemical studies show that poxvirus-encoded A51R proteins block ETS-1 expression by outcompeting structure-specific recognition protein-1 binding to SUMOylated hSpt16 and by tethering SUMOylated hSpt16 to microtubules. Furthermore, A51R antagonism of FACT enhances poxvirus replication in human cells and virulence in mice. Finally, we show that FACT also restricts rhabdoviruses, flaviviruses and orthomyxoviruses, suggesting broad roles for FACT in antiviral immunity. Our study reveals the FACT-ETS-1 antiviral response (FEAR) pathway to be critical for eukaryotic antiviral immunity and describes a unique mechanism of viral immune evasion. Overall design: A549 cells stably expressing control (pLKO1) or hSpt16 shRNA from transduced lentiviruses were mock-infected or infected with DA51RFA51R or DA51R strains for 1 h (MOI = 50). Following infection, complete media was added and incubated until 4 hpi when cells were lysed and total RNA was extracted for library preparations. All infection treatments were performed in triplicate for a total of 18 samples (libraries) to be analyzed. Control