Potential roles for ubiquitin and the proteasome during ribosome biogenesis.
We have investigated the possible involvement of the ubiquitin-proteasome system (UPS) in ribosome biogenesis. We find by immunofluorescence that ubiquitin is present within nucleoli and also demonstrate by immunoprecipitation that complexes associated with pre-rRNA processing factors are ubiquitinated. Using short proteasome inhibition treatments, we show by fluorescence microscopy that nucleolar morphology is disrupted for some but not all factors involved in ribosome biogenesis. Interference with proteasome degradation also induces the accumulation of 90S preribosomes, alters the dynamic properties of a number of processing factors, slows the release of mature rRNA from the nucleolus, and leads to the depletion of 18S and 28S rRNAs. Together, these results suggest that the UPS is probably involved at many steps during ribosome biogenesis, including the maturation of the 90S preribosome.
Stavreva
Diana A
DA
Laboratory of Receptor Biology and Gene Expression, Center for Cancer Research [corrected] National Cancer Institute, Bethesda, MD 20892, USA.
Kawasaki
Miyuki
M
Dundr
Miroslav
M
Koberna
Karel
K
Müller
Waltraud G
WG
Tsujimura-Takahashi
Teruko
T
Komatsu
Wataru
W
Hayano
Toshiya
T
Isobe
Toshiaki
T
Raska
Ivan
I
Misteli
Tom
T
Takahashi
Nobuhiro
N
McNally
James G
JG
D002460:Cell Line; D002466:Cell Nucleolus / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D061988:Proteasome Inhibitors; D012322:RNA Precursors / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D012337:RNA, Ribosomal, 18S / Q000235:genetics / Q000378:metabolism; D012339:RNA, Ribosomal, 28S / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D025801:Ubiquitin / Q000032:analysis / Q000378:metabolism*
D009687:Nuclear Proteins; D061988:Proteasome Inhibitors; D012322:RNA Precursors; D012337:RNA, Ribosomal, 18S; D012339:RNA, Ribosomal, 28S; D025801:Ubiquitin; D046988:Proteasome Endopeptidase Complex