Nucleation by rRNA Dictates the Precision of Nucleolus Assembly.

TitleNucleation by rRNA Dictates the Precision of Nucleolus Assembly.
Publication TypeJournal Article
Year of Publication2016
AuthorsFalahati, H, Pelham-Webb, B, Blythe, S, Wieschaus, E
JournalCurr Biol
Date Published2016 Feb 08
KeywordsAnimals, Cell Nucleolus, DNA, Ribosomal, Drosophila melanogaster, Embryo, Nonmammalian, Nuclear Proteins, RNA, Ribosomal, Transcription, Genetic

<p>Membrane-less organelles are intracellular compartments specialized to carry out specific cellular functions. There is growing evidence supporting the possibility that such organelles form as a new phase, separating from cytoplasm or nucleoplasm. However, a main challenge to such phase separation models is that the initial assembly, or nucleation, of the new phase is typically a highly stochastic process and does not allow for the spatiotemporal precision observed in biological systems. Here, we investigate the initial assembly of the nucleolus, a membrane-less organelle involved in different cellular functions including ribosomal biogenesis. We demonstrate that the nucleolus formation is precisely timed in D. melanogaster embryos and follows the transcription of rRNA. We provide evidence that transcription of rRNA is necessary for overcoming the highly stochastic nucleation step in the formation of the nucleolus, through a seeding mechanism. In the absence of rDNA, the nucleolar proteins studied are able to form high-concentration assemblies. However, unlike the nucleolus, these assemblies are highly variable in number, location, and time at which they form. In addition, quantitative study of the changes in the nucleoplasmic concentration and distribution of these nucleolar proteins in the wild-type embryos is consistent with the role of rRNA in seeding the nucleolus formation.</p>

Alternate JournalCurr Biol
PubMed ID26776729
PubMed Central IDPMC5866055
Grant List5R37HD15587 / HD / NICHD NIH HHS / United States
1F32HD072653 / HD / NICHD NIH HHS / United States
/ / Howard Hughes Medical Institute / United States
R01 HD015587 / HD / NICHD NIH HHS / United States
P30 CA008748 / CA / NCI NIH HHS / United States
T32 HG003284 / HG / NHGRI NIH HHS / United States