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. The RNA exosome may be involved in Ig class switch recombination (CSR) and/or Ig variable region somatic hypermutation (SHM) by targeting AICDA deamination activity to transcribed dsDNA substrates. 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. It seems to be involved in degradation of histone mRNA. The catalytic inactive RNA exosome core complex of 9 subunits (Exo-9) is proposed to play a pivotal role in the binding and presentation of RNA for ribonucleolysis, and to serve as a scaffold for the association with catalytic subunits and accessory proteins or complexes. EXOSC8 binds to ARE-containing RNAs. Component of the RNA exosome complex (PubMed:29906447). Specifically part of the catalytically inactive RNA exosome core (Exo-9) complex which is believed to associate with catalytic subunits EXOSC10, and DIS3 or DIS3L in cytoplasmic- and nuclear-specific RNA exosome complex forms. Exo-9 is formed by a hexameric ring of RNase PH domain-containing subunits specifically containing the heterodimers EXOSC4-EXOSC9, EXOSC5-EXOSC8 and EXOSC6-EXOSC7, and peripheral S1 domain-containing components EXOSC1, EXOSC2 and EXOSC3 located on the top of the ring structure. Binds outer membrane protein opap from Neisseria gonorrhoeae. The disease is caused by variants affecting the gene represented in this entry. EXOSC8 dysfunction causes myelin disruption through an imbalanced supply of myelin proteins due to dysregulation of their ARE-containing mRNAs (PubMed:24989451). Belongs to the RNase PH family. The six exosome core subunits containing a RNase PH-domain are not phosphorolytically active.