The nucleolus is a subnuclear organelle formed
around the ribosomal DNA (rDNA) repeats, which cluster at chromosomal
loci called nucleolar organizing regions (NORs). It is the factory
in which 28S, 18S and 5.8S ribosomal RNAs (rRNAs) are transcribed,
processed and assembled into ribosomal subunits.
In addition to its major role in ribosome production, the nucleolus
may also be involved in messenger RNA (mRNA) export or degradation.
Recent studies suggest that the mammalian nucleolus may also
play roles in tumourigenesis, viral replication and cellular
stress sensoring. However, the pathway and the identities of
the molecular machineries involved in these mechanisms within
this nuclear organelle remain largely unknown. |
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Due to its inherent high density,
nucleoli from cultured human cells can be isolated in great
quantities from sonicated nuclear extracts. Taking advantage
of this, our laboratory and others have previously employed
various mass spectrometry techniques to identify the protein
components from highly purified nucleolar preparations. Visit
our Protocols page for a detailed
nucleolar isolation protocol, including still images and Quicktime
movies demonstrating key steps. |
Fluorescent protein-tagging experiments and photobleaching
analyses have demonstrated the dynamic nature of the nucleolar
proteome, where proteins accumulate in the nucleolus only under
specific metabolic conditions or at specific cell cycle stages.
Recently, we have extended our mass spectrometry analyses to
measure the dynamic behaviour of the nucleolar proteome by quantitating
the relative level of individual nucleolar components upon transcriptional
inhibition using a method known as Stable Isotope Labelling
with Amino acids in Cell Culture (SILAC). For more details visit
our Proteomics page. |
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For more information, check out our "Science at a Glance"
poster and article in the Journal of Cell Science:
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