Viral Virtuosos | The Scientist Magazine®

A diverse, abundant, and underappreciated viral community exists on and within us, from our skin to our eyes, blood, brain, and other organs—even within our own genomes.1 Unlike marauding Ebola-like viruses, these viruses establish a balanced coexistence that can persist for a host’s entire lifetime. This coexistence involves careful control of the viral life cycle: whereas Ebola virus infection is flashy, persistent infection is elegant.

Among other challenges, persistent viruses must effectively subvert the host immune response. To accomplish this, these viruses control both the timing and amount of viral replication. Such nuanced infectious cycles involve carefully choreographed viral gene expression that can foster completely different lifestyles depending on host cell type, cell-signaling events, or other factors. One important class of regulators that helps to mediate these lifestyle switches is the noncoding regulatory RNAs (ncRNAs), which today stand at the center of an ongoing mini-revolution in our understanding of gene-expression control.

Previously thought of as a simple decoder of genetic information—serving as an intermediate between DNA and protein—RNA is now known to engage in a bevy of other important biochemical activities. Despite differences in ncRNA sequence, size, and function, a theme is emerging: diverse biological processes rely on ncRNAs to balance the timing and magnitude of gene expression.2 In eukaryotes, microRNAs (miRNAs) represent the best-characterized ncRNAs. About 22 nucleotides in length, these small RNAs bind to and repress target messenger RNA (mRNA) transcripts, allowing for fine-tuning of gene expression. The human genome encodes hundreds of different miRNAs to regulate numerous biological functions, and recent research is revealing how the viruses of the human body use these miRNAs, as well as their own, to establish and maintain long-term persistent infections.

No comments: