The RNA Exosomes
RNA exosomes are large multimeric 3′-5′ exo- and endonucleases found in eukaryotes and many archaeal species. They represent the central RNA 3′-end processing factor and are implicated in processing, quality control, and turnover of both coding and noncoding RNAs. RNA exosomes are highly regulated and processive machineries, assembled as large macromolecular cages that channel RNA to the ribonuclease sites. The primordial exosome – found in archaea and related to bacterial and organelle degradosomes – possesses a phosphorolytic active cage that can both degrade and polyadenylate RNA in RNA decay processes. Human and yeast exosomes lost phosphorolytic activities but gained ectopic subunits with hydrolytic activities, while preserving the RNA channeling function.
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