title: Exosome substrate targeting: the long and short of it.
abstract: The exosome ribonuclease complex functions in both the limited trimming of the 3'-ends of nuclear substrates during RNA processing events and the complete destruction of nuclear and cytoplasmic RNAs. The two RNases of the eukaryotic exosome, Rrp44 (rRNA-processing protein 44) and Rrp6, are bound at either end of a catalytically inert cylindrical core. RNA substrates are threaded through the internal channel of the core to Rrp44 by RNA helicase components of the nuclear TRAMP complex (Trf4-Air2-Mtr4 polyadenylation complex) or the cytoplasmic Ski (superkiller) complex. Recent studies reveal that Rrp44 can also associate directly with substrates via channel-independent routes. Although the substrates of the exosome are known, it is not clear whether specific substrates are restricted to one or other pathway. Data currently available support the model that processed substrates are targeted directly to the catalytic subunits, whereas at least some substrates that are directed towards discard pathways must be threaded through the exosome core.
authors.affiliation: *Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, U.K.
authors.forename: Phil
authors.initials: P
authors.lastname: Mitchell
mesh_terms: D000818:Animals; D063326:Exosome Multienzyme Ribonuclease Complex / Q000378:metabolism*; D055354:Exosomes / Q000378:metabolism*; D006801:Humans; D012260:Ribonucleases / Q000378:metabolism
chemical_list: D063326:Exosome Multienzyme Ribonuclease Complex; D012260:Ribonucleases