RRP1B Targets PP1 to Mammalian Cell Nucleoli and Is Associated with Pre-60S Ribosomal Subunits

Delphine Chamousset, Veerle De Wever, Greg B. Moorhead, Yan Chen, Francois-Michel Boisvert, Angus I. Lamond, Laura Trinkle-Mulcahy

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    Abstract

    A pool of protein phosphatase 1 (PP1) accumulates within nucleoli and accounts for a large fraction of the serine/threonine protein phosphatase activity in this subnuclear structure. Using a combination of fluorescence imaging with quantitative proteomics, we mapped the subnuclear localization of the three mammalian PP1 isoforms stably expressed as GFP-fusions in live cells and identified RRP1B as a novel nucleolar targeting subunit that shows a specificity for PP1 beta and PP1 gamma. RRP1B, one of two mammalian orthologues of the yeast Rrp1p protein, shows an RNAse-dependent localization to the granular component of the nucleolus and distributes in a similar manner throughout the cell cycle to proteins involved in later steps of rRNA processing. Quantitative proteomic analysis of complexes containing both RRP1B and PP1 gamma revealed enrichment of an overlapping subset of large (60S) ribosomal subunit proteins and pre-60S nonribosomal proteins involved in mid-late processing. Targeting of PP1 to this complex by RRP1B in mammalian cells is likely to contribute to modulation of ribosome biogenesis by mechanisms involving reversible phosphorylation events, thus playing a role in the rapid transduction of cellular signals that call for regulation of ribosome production in response to cellular stress and/or changes in growth conditions.

    Original languageEnglish
    Pages (from-to)4212-4226
    Number of pages15
    JournalMolecular Biology of the Cell
    Volume21
    Issue number23
    DOIs
    Publication statusPublished - 1 Dec 2010

    Keywords

    • PROTEIN PHOSPHATASE 1
    • CATALYTIC SUBUNIT
    • MASS-SPECTROMETRY
    • DOCKING MOTIF
    • IDENTIFICATION
    • LOCALIZATION
    • DYNAMICS
    • INTERACTOME
    • COMPONENTS
    • REGULATORS

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