miRNAs: biogenesis, origin and evolution, functions on virus-host interaction.

MicroRNAs (miRNAs) are small endogenous non-coding functional RNAs. They can play vital roles in post-transcriptional regulating mRNAs transcripts in nearly all biological processes. More and more reports on miRNAs come from different species (animal, plant, bacteria, virus) in the researches in development, immunity, apoptosis, tumor, virus-host interaction. These recent findings provide new insights into the roles of miRNAs as well as their function. This review outlines the ever-deepening understanding of miRNAs (biogenesis, origin, evolution), and discusses functions from host and viral miRNAs in the context of virus-host interaction.