Surveillance of nuclear-restricted pre-ribosomes within a subnucleolar region of Saccharomyces cerevisiae.
We previously hypothesized that HEAT-repeat (Huntington, elongation A subunit, TOR) ribosome synthesis factors function in ribosome export. We report that the HEAT-repeat protein Sda1p is a component of late 60S pre-ribosomes and is required for nuclear export of both ribosomal subunits. In strains carrying the ts-lethal sda1-2 mutation, pre-60S particles were rapidly degraded following transfer to 37 degrees C. Polyadenylated forms of the 27S pre-rRNA and the 25S rRNA were detected, suggesting the involvement of the Trf4p/Air/Mtr4p polyadenylation complex (TRAMP). The absence of Trf4p suppressed polyadenylation and stabilized the pre-rRNA and rRNA. The absence of the nuclear exosome component Rrp6p also conferred RNA stabilization, with some hyperadenylation. We conclude that the nuclear-restricted pre-ribosomes are polyadenylated by TRAMP and degraded by the exosome. In sda1-2 strains at 37 degrees C, pre-40S and pre-60S ribosomes initially accumulated in the nucleoplasm, but then strongly concentrated in a subnucleolar focus, together with exosome and TRAMP components. Localization of pre-ribosomes to this focus was lost in sda1-2 strains lacking Trf4p or Rrp6p. We designate this nucleolar focus the No-body and propose that it represents a site of pre-ribosome surveillance.
Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, UK.
Christophe
C
Dez
Jonathan
J
Houseley
David
D
Tollervey
D021581:Active Transport, Cell Nucleus; D018797:Cell Cycle Proteins / Q000235:genetics; D002466:Cell Nucleolus / Q000235:genetics / Q000378:metabolism; D053487:DEAD-box RNA Helicases; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics; D026723:Polyadenylation; D020365:RNA Helicases / Q000235:genetics / Q000378:metabolism; D012322:RNA Precursors / Q000235:genetics / Q000502:physiology*; D012270:Ribosomes / Q000235:genetics / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D013696:Temperature
D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; D012322:RNA Precursors; C409685:SDA1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D004259:DNA-Directed DNA Polymerase; C487545:PAP2 protein, S cerevisiae; C101004:MTR4 protein, S cerevisiae; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases