Flipping the script: viral capitalization of RNA modifications.

RNA encoded by RNA viruses is highly regulated so that it can function in multiple roles during the viral life cycle. These roles include serving as the mRNA template for translation or the genetic material for replication as well as being packaged into progeny virions. RNA modifications provide an emerging regulatory dimension to the RNA of viruses. Modification of the viral RNA can increase the functional genomic capacity of the RNA viruses without the need to encode and translate additional genes. Further, RNA modifications can facilitate interactions with host or viral RNA-binding proteins that promote replication or can prevent interactions with antiviral RNA-binding proteins. The mechanisms by which RNA viruses facilitate modification of their RNA are diverse. In this review, we discuss some of these mechanisms, including exploring the unknown mechanism by which the RNA of viruses that replicate in the cytoplasm could acquire the RNA modification N6-methyladenosine.