The reovirus μ2 protein, an enigmatic multifunctional protein with numerous secrets yet to be uncovered

Viruses as obligate intracellular parasites are limited by their small genome. They have thus developed various strategies to maximize viral fitness with a limited amount of coding information. Among these strategies is the use of the same viral protein for multiple functions. The μ2 protein of mammalian reovirus is one such example of a multifunctional protein. We will present recent progress in our understanding of some functions and properties of this protein that have been revealed in the last two or three decades, such as its impact on the formation of viral factories or the control of the interferon response. We will also examine the recently established structure of the protein and the most recent data on the protein's enzymatic activities in the context of viral RNA synthesis. Finally, the impact of μ2 in the regulation of host-cell alternative mRNA splicing will be presented and future avenues of research discussed.