Signal recognition particle assembly in relation to the function of amplified nucleoli of Xenopus oocytes

John Sommerville, CL Brumwell, JC Ritland Politz, T Pederson

Research output: Contribution to journalArticlepeer-review

27 Citations (Scopus)

Abstract

The signal recognition particle (SRP) is a ribonucleoprotein machine that controls the translation and intracellular sorting of membrane and secreted proteins. The SRP contains a core RNA subunit with which six proteins are assembled. Recent work in both yeast and mammalian cells has identified the nucleolus as a possible initial site of SRP assembly. In the present study, SRP RNA and protein components were identified in the extrachromosomal, amplified nucleoli of Xenopus laevis oocytes. Fluorescent SRP RNA microinjected into the oocyte nucleus became specifically localized in the nucleoli, and endogenous SRP RNA was also detected in oocyte nucleoli by RNA in situ hybridization. An initial step in the assembly of SRP involves the binding of the SRP19 protein to SRP RNA. When green fluorescent protein (GFP)-tagged SRP19 protein was injected into the oocyte cytoplasm it was imported into the nucleus and became concentrated in the amplified nucleoli. After visiting the amplified nucleoli, GFP-tagged SRP19 protein was detected in the cytoplasm in a ribonucleoprotein complex, having a sedimentation coefficient characteristic of the SRP. These results suggest that the amplified nucleoli of Xenopus oocytes produce maternal stores not only of ribosomes, the classical product of nucleoli, but also of SRP, presumably as a global developmental strategy for stockpiling translational machinery for early embryogenesis.

Original languageEnglish
Pages (from-to)1299-1307
Number of pages9
JournalJournal of Cell Science
Volume118
Issue number6
DOIs
Publication statusPublished - 15 Mar 2005

Keywords

  • immunohistochemistry
  • in situ hybridization
  • microinjection
  • nuclear organization
  • nucleolar function
  • CRYSTAL-STRUCTURE
  • AMPHIBIAN OOGENESIS
  • RIBOSOMAL-RNA
  • ALU DOMAIN
  • SRP-RNA
  • GERMINAL VESICLE
  • MAMMALIAN-CELLS
  • CAJAL BODY
  • PROTEIN
  • LAEVIS

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