CDC42 and infection: Using a high throughput siRNA screen, Nomura et al. [63] demonstrated that silencing of two major constituents of the Arp2/3 complex resulted in significant reduction if MHV infectivity, and use of actin cytoskeleton altering agents in the early stages of infection had similar restrictive effects on infection, pointing to GTPase, and specifically Cdc42 involvement in the entry process.