Non-catalytic component of the RNA exosome complex which has 3'->5' exoribonuclease activity and participates in a multitude of cellular RNA processing, maturation and degradation events. In vitro, is an active and distributive 3'->5' exonuclease requiring a free 3'-OH on the substrate and releasing nucleoside 5'-monophosphates (PubMed:11809881). Required for normal embryo development (PubMed:18160042). Component of the RNA exosome complex (PubMed:11809881, PubMed:18160042). Interacts with RPP41 (PubMed:11809881). Expressed in roots, stems, rosette and cauline leaves, flowers and siliques. The two RNA-binding domains (S1 motif and KH domain) are separated by a conserved linker of five amino acids (KYGKL) and can bind RNA independently. Both domains are also needed for RNA degradation and interaction with RRP41, another exosome subunit. Embryonic lethality due to embryo developmental arrest at early globular stage. Belongs to the RRP4 family.