Double-stranded RNA is a warning flag to the cell, indicating the presence of a virus. In 2004, Takashi Fujita and colleagues at Tokyo Metropolitan Institute of Medical Science identified an RNA-helicase, retinoic acid inducible gene I (RIG-I), as linking dsRNA and the interferon response.
Robert Lamb at Northwestern University in Evanston, Ill., says that as a consequence, "investigations are being conducted on just about every virus as to interactions with mda-5 and RIG-I."
Questions remain. While dsRNA can activate both mda-5 and RIG-I, Randall says it's unclear whether they recognize slightly different forms of dsRNA or other viral structures. "Also, it needs to be established whether or not some form of regulatory crosstalk occurs between mda-5, RIG-I and other cellular signaling cascades," he adds.