Cellular stress responses induced during
viral infections are critical to the health and survival of organisms. In higher vertebrates,
interferons (IFNs) mediate the innate
antiviral response in part through the action of
RNase L, a uniquely regulated
enzyme.
RNase L is activated by 5'-phosphorylated, 2'-5' oligoadenylates (2-5A) produced from IFN-inducible and
double stranded RNA-dependent
synthetases. We show that viral activation of the c-Jun NH2-terminal
kinases (JNK) family of MAP
kinases and viral induction of apoptosis are both deficient in mouse cells lacking
RNase L. Also, JNK phosphorylation in response to 2-5A was greatly reduced in
RNase L-/- mouse cells. In addition, 2-5A treatment of the human ovarian
carcinoma cell line, Hey1b, resulted in specific
ribosomal RNA cleavage products coinciding with JNK activation. Furthermore, suppression of JNK activity with the chemical inhibitor,
SP600125, prevented apoptosis induced by 2-5A. In contrast, inhibition of alternative MAP
kinases, p38 and ERK, failed to prevent 2-5A-mediated apoptosis.
Short interfering RNA to JNK1/JNK2 mRNAs resulted in JNK ablation while also suppressing 2-5A-mediated apoptosis. Moreover, Jnk1-/- Jnk2-/- cells were highly resistant to the apoptotic effects of IFN and 2-5A. These findings suggest that JNK and
RNase L function in an integrated signaling pathway during the IFN response that leads to elimination of virus-infected cells through apoptosis.