Purification and characterisation of p99, a nuclear modulator of protein phosphatase 1 activity

Jan Peter Kreivi (Lead / Corresponding author), Laura Trinkle-Mulcahy, Carol E. Lyon, Nick A. Morrice, Philip Cohen, Angus I. Lamond

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    70 Citations (Scopus)


    We have purified a form of protein phosphatase 1 (PP1) from HeLa cell nuclei, in which the phosphatase is complexed to a regulatory subunit termed p99. We report here the cloning and characterisation of the p99 component. p99 mRNA is widely expressed in human tissues and immunofluorescence analysis with anti-p99 antibodies showed a punctate nucleoplasmic staining with additional accumulations within the nucleolus. The C-terminus of p99 contains seven RGG RNA-binding motifs, followed by eleven decapeptide repeats containing six or more of the following conserved residues (GHRPHEGPGG), and finally a putative zinc finger domain. Recombinant p99 suppresses the phosphorylase phosphatase activity of PP1 by > 90% and the canonical PP1-binding motif on p99 (residues 396-401) is unusual in that the phenylalanine residue is replaced by tryptophan.

    Original languageEnglish
    Pages (from-to)57-62
    Number of pages6
    JournalFEBS Letters
    Issue number1
    Publication statusPublished - 22 Dec 1997


    • Cell regulation
    • Immunocytochemistry
    • Nucleus
    • Protein phosphatase 1

    ASJC Scopus subject areas

    • Structural Biology
    • Biophysics
    • Biochemistry
    • Molecular Biology
    • Genetics
    • Cell Biology


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