Non-catalytic component of the RNA exosome complex which has 3'->5' exoribonuclease activity and participates in a multitude of cellular RNA processing and degradation events. In the nucleus, the RNA exosome complex is involved in proper maturation of stable RNA species such as rRNA, snRNA and snoRNA, in the elimination of RNA processing by-products and non-coding 'pervasive' transcripts, such as antisense RNA species and promoter-upstream transcripts (PROMPTs), and of mRNAs with processing defects, thereby limiting or excluding their export to the cytoplasm. In the cytoplasm, the RNA exosome complex is involved in general mRNA turnover and specifically degrades inherently unstable mRNAs containing AU-rich elements (AREs) within their 3' untranslated regions, and in RNA surveillance pathways, preventing translation of aberrant mRNAs. Component of the RNA exosome complex. Morpholino knockdown of the protein affects brain and neuromuscular development. Morphant embryos have small heads, small or absent eyes, truncated bodies, and reduced and damaged myofibers. Motor axons fail to migrate properly to the neuromuscular junctions. The brain has abnormal morphology, the cerebellum and hindbrain are absent. Belongs to the RNase PH family. The six exosome core subunits containing a RNase PH-domain are not phosphorolytically active.