The 2′-5′-oligoadenylate synthetase (OAS)/RNase L system protects hosts against pathogenic viruses through cleavage of the exogenous single-stranded RNA. In this system, an evolutionally conserved RNA quality control factor Dom34 (known as Pelota (Pelo) in higher eukaryotes) forms a surveillance complex with RNase L to recognize and eliminate the exogenous RNA in a manner dependent on translation. Here, we newly identified that ATP-binding cassette sub-family E member 1 (ABCE1), which is also known as RNase L inhibitor (RLI), is involved in the regulation of exogenous RNA decay. ABCE1 directly binds to form a complex with RNase L and accelerates RNase L dimer formation in the absence of 2′-5′ oligoadenylates (2-5A). Depletion of ABCE1 represses 2-5A-induced RNase L activation and stabilizes exogenous RNA to a level comparable to that seen in RNase L depletion. The increased half-life of the RNA by the single depletion of either protein is not significantly affected by the double depletion of both proteins, suggesting that RNase L and ABCE1 act together to eliminate exogenous RNA. Our results indicate that ABCE1 functions as a positive regulator of exogenous RNA decay rather than an inhibitor of RNase L.
