Exo- and endoribonucleolytic activities of yeast cytoplasmic and nuclear RNA exosomes are dependent on the noncatalytic core and central channel.
The RNA exosome is an essential multisubunit ribonuclease (RNase) that contributes to cytoplasmic and nuclear RNA decay and quality control. The 9-subunit exosome core (Exo9) features a prominent central channel formed by stacked asymmetric rings of six RNase PH-like proteins and three S1/KH domain proteins. Exo9 is catalytically inert but associates with Rrp44, an endoribonuclease and processive 3'→5' exoribonuclease, and Rrp6, a distributive 3'→5' exoribonuclease. We show that Exo9 and its central channel modulate all three yeast exosome RNase activities because channel occlusion attenuates RNA binding and RNase activities in vitro and fails to complement exosome functions in vivo. We find that Rrp6 stimulates Rrp44 RNase activities and that Rrp6 is inhibited by a mutation in the Rrp44 exoribonuclease active site in 11-subunit nuclear exosomes. These results suggest the exosome core and central channel is essential because it modulates each of the known RNase activities of the yeast RNA exosome.
Structural Biology Program, Sloan-Kettering Institute, New York, NY 10065, USA.
Elizabeth V
EV
Wasmuth
Christopher D
CD
Lima
D020134:Catalytic Domain / Q000235:genetics; D002467:Cell Nucleus / Q000201:enzymology; D003593:Cytoplasm / Q000201:enzymology; D004722:Endoribonucleases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D005095:Exoribonucleases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D063326:Exosome Multienzyme Ribonuclease Complex / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D009154:Mutation; D021122:Protein Subunits; D012331:RNA, Fungal / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D021122:Protein Subunits; D012331:RNA, Fungal; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D004722:Endoribonucleases; D005095:Exoribonucleases; D063326:Exosome Multienzyme Ribonuclease Complex; C542283:DIS3 protein, S cerevisiae; C112610:RRP6 protein, S cerevisiae