A Systematic Analysis of Host Factors Reveals a Med23-Interferon-? Regulatory Axis against Herpes Simplex Virus Type 1 Replication

Griffiths, Samantha J.; Koegl, Manfred; Boutell, Chris; Zenner, Helen L.; Crump, Colin M.; Pica, Francesca; Gonzalez, Orland; Friedel, Caroline C.; Barry, Gerald; Martin, Kim; Craigon, Marie H.; Chen, Rui; Kaza, Lakshmi N.; Fossum, Even; Fazakerley, John K.; Efstathiou, Stacey; Volpi, Antonio; Zimmer, Ralf; Ghazal, Peter; Haas, Jürgen

was selected for validation with deconvoluted siRNAs to confirm the phenotype observed in the primary screen. The effect of the four individual siRNAs (1-4) and a reconstituted SMARTpool (SP) were tested by reverse-transfecting into Hela cells before infecting after 48 h with HSV-1-eGFP (C12) and monitoring replication. Replication slopes were calculated and normalized as described, and compared to the primary screen slope (1u). A heat map of replication slopes was generated where red represents inhibition (replication slope ,0.5) and green represents enhancement (slope .1). The phenotype was considered validated if $2 siRNAs produced the same or better phenotype as the primary screen. (c) Virus specificity of HSV-1 HFs. The effect of HF siRNA SMARTpools on the replication of VZV (a-herpesvirus), hCMV (b-herpesvirus) or Semliki Forest virus (SFV; RNA virus) was determined and compared to HSV-1. Normalized replication 626STDEV of the controls was considered inhibiting/enhancing. doi:10.1371/journal.ppat.1003514.g002 Taken together, these data identify Med23 as a novel anti-viral factor which acts as a key regulator of IFN-l expression by interacting with and enhancing the activity of IRF7, a major transcription factor involved in innate immunity. Our observation of a link between the clinical severity of HSV-1 disease and, a CT/ TT genotype at a SNP known to regulate IFN-l3 secretion demonstrates the significance of IFN-l in the control of HSV-1 replication in vivo. Whilst this study provides no direct link between the IFN-l3 promoter polymorphism and Med23, these associations of IFN-l with HSV-1 disease, combined with our observations that Med23 is required for the induction of IFN-l following HSV-1 infection, identifies for the first time a link between Med23 and IFN-l, provides a clinical context for Med23 regulation of IFN-l expression and underscores the potential biological significance of these data.