Viral RNA Modulation of Host Gene Expression

Viruses depend on and modulate their hosts' cellular environments to maximize replication. Studies of viruses can therefore reveal important aspects of host-pathogen interactions and fundamental cell biology. Viruses often modulate host pathways using proteins, but can also express non-coding RNAs whose functions and mechanisms are mostly unknown. Cazalla and colleagues studied the small RNAs from H. saimiri, a herpesvirus that establishes latency in the T cells of New World primates and can cause aggressive leukemias and lymphomas in non-natural hosts. They showed these RNAs, called HSURs, modulate host gene expression and inhibit host cell death using a novel mechanism in which the HSURs inhibit host mRNAs by tethering them to host miRNAs and the associated degradation and translation inhibition machinery. This mechanism is a completely novel process, not previously observed in cells, and but which promises to lead to a fuller understanding of gene regulation in both infected and uninfected cells.