3'-to-5' exoribonuclease specific for small oligoribonucleotides 2 to 5 nucleotides in length, as well as small (2 to 5 nucleotides) ssDNA oligomers. Probably responsible for the final step in mRNA degradation. Inhibited by adenosine 3',5'-bisphosphate (PAP). Homodimer. Essential. In depletion experiments the level of oligonucleotides is elevated and that of mononucleotides is severely reduced compared to wild-type. Belongs to the oligoribonuclease family. Extended N-terminus.