Autographa californica nucleopolyhedrovirus infection of Spodoptera frugiperda cells: a global analysis of host gene regulation during infection, using a differential display approach

Department of Biological Sciences, SAF Building, South Kensington Campus, Imperial College, London SW7 2AZ, UK Correspondence Julie Olszewski j.olszewski{at}imperial.ac.uk Autographa californica nucleopolyhedrovirus (AcMNPV), the type member of the virus family Baculoviridae , infects pest insects and has been the subject of many studies for its development as a biopesticide. It is also the virus upon which most of the commercial baculovirus protein expression systems are based. AcMNPV infection of cultured host Spodoptera frugiperda (Sf9) cells can induce a number of alterations of host cell properties including altering the cellular cytoskeleton, an arrest of the cell cycle in G 2 /M, and the global shutoff of host protein translation. Additionally, several cellular transcripts have been shown to be down-regulated following AcMNPV infection. In this study, we take a differential display approach to address whether a global down-regulation of Sf9 host transcripts occurs at late times of infection. Additionally, we also use this approach to search for host mRNAs which are up-regulated at early times of infection, and may be important for facilitating baculovirus infection. From these experiments we can confirm a global down-regulation of Sf9 mRNA levels at late times of infection. We also found that up-regulation of individual host gene RNA levels at early times of infection did not occur frequently. One host transcript which was found to be transiently up-regulated as a result of AcMNPV infection was an Sf9 Hsc70 gene. Hsc70 proteins have been shown to play a vital role in the life-cycle of other large DNA viruses, which suggests that this protein is also important for baculovirus infection. Present address: INRA, Unité de Virologie et Immunologie moléculaires, 78350 Jouy-en-Josas, France. Present address: Syngenta, Jealotts Hill International Research Centre, Bracknell, Berkshire RG42 6EY, UK.