To study Ub-dependent mechanisms involved in RIG-I signaling, Zeng et al. (2010) developed a cell-free model of viral infection that combines purified RIG-I protein, mitochondrial and cytosolic extracts, RNA, and ubiquitination enzymes, using IRF3 dimerization as a reporter for RIG-I and MAVS activity. The gene discussed is IRF3; the disease is viral infectious disease.