Impact of RNase L overexpression on viral and cellular growth and death

The biologic actions of interferons (IFNs) are complex and involve multiple biochemical mechanisms, including the 2-5A system, a regulated RNA decay p athway, The 2-5A system is implicated in the antipicornavirus activity of I FN and in the control of apoptosis, To further investigate involvement of t he 2-5A system in the control of viral and cellular growth and death, human RNase L cDNA was stably expressed in murine 3T3 cells from a constitutive cytomegalovirus (CMV) promoter. A clonal cell line, 3T3/pLZ, was isolated t hat overexpressed RNase L by >100-fold compared with levels of the endogeno us murine RNase L, Interestingly, human RNase L levels in 3T3/pLZ cells dec reased 3-fold as cells entered a confluent, growth arrest state, suggesting autoregulation. Overexpression of human RNase L greatly enhanced both the cell growth inhibitory activity of IFN and the proapoptotic activity of sta urosporine. Furthermore, high levels of RNase L suppressed the replication of diverse viruses: encephalomyocarditis virus, vesicular stomatitis virus, human parainfluenza virus-3, and vaccinia virus, Additional reductions in viral growth were obtained by treating 3T3/pLZ cells with IFN (alpha + beta ) before infections, These results directly demonstrate the anticellular an d antiviral potential of the 2-5A system.