Molecular composition of IMP1 ribonucleoprotein granules.

Lars Jønson, Jonas Vikesaa, Anders Krogh, Lars K Nielsen, Thomas vO Hansen, Rehannah Borup, Anders H Johnsen, Jan Christiansen, Finn C Nielsen

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181 Citations (Scopus)

Abstract

Localized mRNAs are transported to sites of local protein synthesis in large ribonucleoprotein (RNP) granules, but their molecular composition is incompletely understood. Insulin-like growth factor II mRNA-binding protein (IMP) zip code-binding proteins participate in mRNA localization, and in motile cells IMP-containing granules are dispersed around the nucleus and in cellular protrusions. We isolated the IMP1-containing RNP granules and found that they represent a unique RNP entity distinct from neuronal hStaufen and/or fragile X mental retardation protein granules, processing bodies, and stress granules. Granules were 100-300 nm in diameter and consisted of IMPs, 40 S ribosomal subunits, shuttling heterologous nuclear RNPs, poly(A)-binding proteins, and mRNAs. Moreover granules contained CBP80 and factors belonging to the exon junction complex and lacked eIF4E, eIF4G, and 60 S ribosomal subunits, indicating that embodied mRNAs are not translated. Granules embodied mRNAs corresponding to about 3% of the human embryonic kidney 293 mRNA transcriptome. Messenger RNAs encoding proteins participating in the secretory pathway and endoplasmic reticulum-associated quality control, as well as ubiquitin-dependent metabolism, were enriched in the granules, reinforcing the concept of RNP granules as post-transcriptional operons.
Original languageEnglish
JournalMolecular and Cellular Proteomics
Volume6
Issue number5
Pages (from-to)798-811
Number of pages13
ISSN1535-9476
DOIs
Publication statusPublished - 2007

Bibliographical note

Keywords: Cell Line; Cytoskeletal Proteins; Fragile X Mental Retardation Protein; Humans; Metabolic Networks and Pathways; Microscopy, Atomic Force; Proteomics; RNA, Messenger; RNA-Binding Proteins; Ribonucleoproteins

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