In the nucleus,the RNA exosome complex is involved in proper maturation of stable RNA species such as rRNA,snoRNA and snRNA,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 . EXOSC2 is a non-catalytic component of the RNA exosome complex that has 3'->5' exoribonuclease activity and involves in a multitude of cellular RNA processing and degradation events .