2-5A-dependent ribonuclease (RNASEL) is an endoribonuclease that is activated in the interferon (IFN) antiviral response. Its anti-viral effects are probably a combination of induction of apoptosis, cleavage of viral mRNA and induction of other anti-viral genes. ATP-binding cassette sub-family E member 1 (ABCE1, aka RNase L inhibitor, RLI) directly interacts with RNASEL and inhibits its endoribonuclease activity, thus antagonising the anti-viral effect of the IFN-regulated 2-5A/RNase L pathway (Martinand et al. 1998, Martinand et al. 1999, Le Roy et al. 2001).