Viral evasion of cellular defense mechanisms: regulation of the protein kinase DAI by RNA effectors

The protein kinase DAI (the double-stranded RNA activated inhibitor) plays a critical role in controlling translation in uninfected and infected cells. It is induced by interferon as part of the cellular antiviral defense mechanism. When activated, it leads to a blockade of polypeptide chain initiation, thereby interrupting viral propagation. Many viruses have developed means to neutralize the action of DAI: the sheer profusion of these countermeasures makes it clear that DAI is an important component of the host antiviral defense mechanism and a serious concern to the viruses. This chapter focusses on the mechanism of DAI activation and its inhibition by virus-encoded RNA antidotes.