Perinuclear P granules are the principal sites of mRNA export in adult C. elegans germ cells.
Germline-specific granules of unknown function are found in a wide variety of organisms, including C. elegans, where they are called P granules. P granules are cytoplasmic bodies in oocytes and early embryos. Throughout most of the C. elegans life cycle, however, P granules are associated with clusters of nuclear pore complexes (NPCs) on germ cell nuclei. We show that perinuclear P granules differ from cytoplasmic P granules in many respects, including structure, stability and response to metabolic changes. Our results suggest that nuclear-associated P granules provide a perinuclear compartment where newly exported mRNAs are collected prior to their release to the general cytoplasm. First, we show that mRNA export factors are highly enriched at the NPCs associated with P granules. Second, we discovered that the expression of high-copy transgenes could be induced in a subset of germ cells, and used this system to demonstrate that nascent mRNA traffics directly to P granules. P granules appear to sequester large amounts of mRNA in quiescent germ cells, presumably preventing translation of that mRNA. However, we did not find evidence that P granules normally sequester aberrant mRNAs, or mRNAs targeted for destruction by the RNAi pathway.
Sheth
Ujwal
U
Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.
Pitt
Jason
J
Dennis
Shannon
S
Priess
James R
JR
D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism; D002467:Cell Nucleus / Q000502:physiology / Q000648:ultrastructure; D003593:Cytoplasm / Q000502:physiology; D053487:DEAD-box RNA Helicases / Q000235:genetics; D012734:Disorders of Sex Development / Q000235:genetics; D005854:Germ Cells / Q000166:cytology / Q000502:physiology; D029543:Nucleocytoplasmic Transport Proteins / Q000378:metabolism; D009865:Oocytes / Q000166:cytology / Q000502:physiology; D012313:RNA / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism
D029742:Caenorhabditis elegans Proteins; C418480:NXF-1 protein, C elegans; D029543:Nucleocytoplasmic Transport Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D012313:RNA; D053487:DEAD-box RNA Helicases