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

Understanding the complex interplay between viral and host components is critical to the definition of herpesvirus infection and pathogenesis. As herpesviruses encode a large number of proteins, in contrast to small RNA viruses such as HIV and Influenza, many cellular processes may be directly affected by viral proteins, and whilst there exists a wealth of information on individual viral proteins, there remain large gaps in our understanding of the HSV-1 life cycle and its interaction with its host. Here, we present data from the first integrative and systematic screening approach to characterise the role of cellular proteins in the HSV-1 life cycle. A genome-scale RNAi knockdown screen to identify HFs functionally influencing HSV-1 replication was performed in parallel with a yeast two-hybrid (Y2H) protein interaction screen to simultaneously gain insight into potential mechanisms of action. Combined analyses confirmed the importance of known cellular proteins involved in processes such as cell cycle, proteins transport and gene expression important for virus replication. Furthermore, we identified a subunit of the Mediator multi-protein complex, Med23, as a key regulator of IFN-l induction, which appears to be of crucial significance for the control of HSV-1 both in vitro and in vivo. These data demonstrate the power of a combined screening strategy to investigate pathogen:host interactions and identify novel host factors and cellular pathway targets for the development of essential clinical interventions.