Represses the expression of non-poly(A) mRNAs like L-A or M viruses and is therefore involved in antiviral system. Mediates interactions via its N-terminus between the exosome and the SKI complex which operate in the 3'-to-5' mRNA-decay pathway. By interacting with NAM7, is also required for nonsense-mediated 3'-to-5' mRNA-decay (NMD). May recognize a stalled 80S ribosome at the 3'-end of a nonstop mRNA which leads to the recruitment of the exosome and SKI complexes to the mRNAs to be degraded. Interacts with the exosome and with the SKI complex composed of at least SKI2, SKI3 and SKI8. Interacts directly with SKI3 and SKI8. The N-terminal domain (residues 1 to 264) is required and sufficient for interaction with the exosome and SKI complexes and for 3'-to-5' mRNA degradation. Present with 233 molecules/cell in log phase SD medium. Belongs to the TRAFAC class translation factor GTPase superfamily. Classic translation factor GTPase family.