Viral Virtuosos
New understanding of noncoding RNAs may solve a long-standing puzzle about how viruses orchestrate lifelong infections.
When it comes to viruses, those that transiently infect their hosts and cause the most damage get a lot of attention. Hollywood makes movies about Ebola, or about fictional viruses that resemble souped-up versions of the 1918 pandemic flu. Another viral world—one much closer to home—rarely enters the collective consciousness: the human virome.
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. (See illustration.)
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.
