MicroRNA expression and functions in viral infections.

MicroRNAs (miRNAs) are small, noncoding RNAs that have emerged as powerful players in the post-transcriptional regulation of gene expression. In the context of viral infections, cellular miRNAs play significant roles in modulating the complex host responses to pathogens and have essential roles in shaping viral replication. Moreover, several virus families encode viral miRNAs that manipulate the host environment and can tap into miRNA-regulated gene networks. Viral antigen expression itself can be directly miRNA regulated, and infection outcomes are substantially shaped by the miRNA activities that influence host anti-viral defense mechanisms. This review discusses common themes for both human and viral miRNAs in viral infection processes, highlighting their dual functions in both suppressing and promoting viral life cycles.