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Surveillance of nuclear‐restricted pre‐ribosomes within a subnucleolar region of Saccharomyces cerevisiae
Author(s) -
Dez Christophe,
Houseley Jonathan,
Tollervey David
Publication year - 2006
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/sj.emboj.7601035
Subject(s) - ribosome , library science , genetics , biology , gene , computer science , rna
We previously hypothesized that HEAT‐repeat ( H untington, e longation A subunit, T OR) 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°C. Polyadenylated forms of the 27S pre‐rRNA and the 25S rRNA were detected, suggesting the involvement of the Tr f4p/ A ir/ M tr4p p olyadenylation 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°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.