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Gene Review

PPP1R8  -  protein phosphatase 1, regulatory subunit 8

Homo sapiens

Synonyms: ARD-1, ARD1, NIPP-1, NIPP1, Nuclear inhibitor of protein phosphatase 1, ...
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Disease relevance of PPP1R8

  • In H1299 and A549 lung cancer cells, hARD1-silencing RNA inhibited cell proliferation and induced G(1) arrest [1].
  • In addition, infection of HeLa MAGI cells with adeno-associated virus-NIPP1 prior to the infection with HIV-1 significantly reduced the level of HIV-1 replication [2].
  • ARD 1 mRNAs of 3.7 and 4.1 kilobases were detected in all rat tissues as well as in mouse and rabbit brain, human fibroblasts, and human neuroblastoma cells but not in HL-60 cells [3].
  • Here we demonstrate that the level of human ARD1 (hARD1) protein is not decreased in hypoxia [4].
  • However, recombinant hARD1 from Escherichia coli was produced with partial N-terminal acetylation and was observed to undergo slow self-mediated N-terminal acetylation [5].

High impact information on PPP1R8


Biological context of PPP1R8


Anatomical context of PPP1R8

  • The nuclear protein NIPP1 (nuclear inhibitor of protein Ser/Thr phosphatase-1) interacts with the splicing factors SAP155 and CDC5L and is involved in a late step of spliceosome assembly [12].
  • NIPP-1alpha mRNA represents the major transcript in human tissues and various cell lines, and encodes a polypeptide of 351 residues that only differs from the previously cloned calf thymus NIPP-1 by a single residue [9].
  • CDC5L and NIPP1 co-localized in nuclear speckles in COS-1 cells [13].
  • When expressed in COS-1 or HeLa cells, the FHA domain of NIPP1 did not affect the number of cells in the G(2)/M transition [13].
  • Translation of NIPP-1 mRNA in reticulocyte lysates resulted in the accumulation of both intact NIPP-1 and a smaller polypeptide generated by alternative initiation at the codon corresponding to Met143 [11].

Associations of PPP1R8 with chemical compounds


Physical interactions of PPP1R8

  • We show here that the FHA domain of NIPP1 interacts in vitro and in vivo with a TP dipeptide-rich fragment of the splicing factor SAP155/SF3b(155), a component of the U2 small nuclear ribonucleoprotein particle [16].

Regulatory relationships of PPP1R8

  • Remarkably, while both NIPP1 domains inhibited the phosphorylase phosphatase activity of PP1(C) independently, mutation of either domain completely abolished the ability of NIPP1 to inhibit the dephosphorylation of myelin basic protein [17].

Other interactions of PPP1R8

  • We report here the cloning and structural characterization of the human NIPP-1 genes, designated PPP1R8P and PPP1R8 in human gene nomenclature [9].
  • Inhibition of spliceosome assembly by the cell cycle-regulated protein kinase MELK and involvement of splicing factor NIPP1 [7].
  • NIPP1-mediated interaction of protein phosphatase-1 with CDC5L, a regulator of pre-mRNA splicing and mitotic entry [13].
  • We discuss how the interaction between NIPP1 and SAP155 could contribute to spliceosome (dis)assembly and the catalytic steps of splicing [16].
  • The in vitro splicing of beta-globin pre-mRNA was not affected by exogenous wild type NIPP1 but was blocked by mutants that lacked residues 225-329 [18].

Analytical, diagnostic and therapeutic context of PPP1R8

  • Site-directed mutagenesis furthermore showed that this spliceosomal function of NIPP1 was unrelated to its ability to bind PP1 or RNA [18].
  • Furthermore, an interaction between CDC5L, NIPP1, and PP1 in rat liver nuclear extracts could be demonstrated by co-immunoprecipitation and/or co-purification experiments [13].
  • Molecular cloning of NIPP-1, a nuclear inhibitor of protein phosphatase-1, reveals homology with polypeptides involved in RNA processing [11].
  • Western blotting with antibodies against the COOH terminus of NIPP-1, however, showed a single polypeptide of 47 kDa, which was enriched in the nucleus [11].
  • Closer sequence analysis revealed novel alternatively spliced variants of Nek2A and NIPP1, which we designated Nek2A-T and NIPP1-T, respectively [19].


  1. Human Arrest Defective 1 Acetylates and Activates {beta}-Catenin, Promoting Lung Cancer Cell Proliferation. Lim, J.H., Park, J.W., Chun, Y.S. Cancer Res. (2006) [Pubmed]
  2. Nuclear protein phosphatase-1 regulates HIV-1 transcription. Ammosova, T., Jerebtsova, M., Beullens, M., Voloshin, Y., Ray, P.E., Kumar, A., Bollen, M., Nekhai, S. J. Biol. Chem. (2003) [Pubmed]
  3. ARD 1, a 64-kDa guanine nucleotide-binding protein with a carboxyl-terminal ADP-ribosylation factor domain. Mishima, K., Tsuchiya, M., Nightingale, M.S., Moss, J., Vaughan, M. J. Biol. Chem. (1993) [Pubmed]
  4. Interaction between HIF-1 alpha (ODD) and hARD1 does not induce acetylation and destabilization of HIF-1 alpha. Arnesen, T., Kong, X., Evjenth, R., Gromyko, D., Varhaug, J.E., Lin, Z., Sang, N., Caro, J., Lillehaug, J.R. FEBS Lett. (2005) [Pubmed]
  5. Purified recombinant hARD1 does not catalyse acetylation of Lys532 of HIF-1alpha fragments in vitro. Murray-Rust, T.A., Oldham, N.J., Hewitson, K.S., Schofield, C.J. FEBS Lett. (2006) [Pubmed]
  6. E3 ubiquitin ligase activity of the trifunctional ARD1 (ADP-ribosylation factor domain protein 1). Vichi, A., Payne, D.M., Pacheco-Rodriguez, G., Moss, J., Vaughan, M. Proc. Natl. Acad. Sci. U.S.A. (2005) [Pubmed]
  7. Inhibition of spliceosome assembly by the cell cycle-regulated protein kinase MELK and involvement of splicing factor NIPP1. Vulsteke, V., Beullens, M., Boudrez, A., Keppens, S., Van Eynde, A., Rider, M.H., Stalmans, W., Bollen, M. J. Biol. Chem. (2004) [Pubmed]
  8. Genetic alterations and expression of the protein phosphatase 1 genes in human cancers. Takakura, S., Kohno, T., Manda, R., Okamoto, A., Tanaka, T., Yokota, J. Int. J. Oncol. (2001) [Pubmed]
  9. Organization and alternate splice products of the gene encoding nuclear inhibitor of protein phosphatase-1 (NIPP-1). Van Eynde, A., Pérez-Callejón, E., Schoenmakers, E., Jacquemin, M., Stalmans, W., Bollen, M. Eur. J. Biochem. (1999) [Pubmed]
  10. Properties and phosphorylation sites of baculovirus-expressed nuclear inhibitor of protein phosphatase-1 (NIPP-1). Vulsteke, V., Beullens, M., Waelkens, E., Stalmans, W., Bollen, M. J. Biol. Chem. (1997) [Pubmed]
  11. Molecular cloning of NIPP-1, a nuclear inhibitor of protein phosphatase-1, reveals homology with polypeptides involved in RNA processing. Van Eynde, A., Wera, S., Beullens, M., Torrekens, S., Van Leuven, F., Stalmans, W., Bollen, M. J. Biol. Chem. (1995) [Pubmed]
  12. The protein phosphatase-1 (PP1) regulator, nuclear inhibitor of PP1 (NIPP1), interacts with the polycomb group protein, embryonic ectoderm development (EED), and functions as a transcriptional repressor. Jin, Q., van Eynde, A., Beullens, M., Roy, N., Thiel, G., Stalmans, W., Bollen, M. J. Biol. Chem. (2003) [Pubmed]
  13. NIPP1-mediated interaction of protein phosphatase-1 with CDC5L, a regulator of pre-mRNA splicing and mitotic entry. Boudrez, A., Beullens, M., Groenen, P., Van Eynde, A., Vulsteke, V., Jagiello, I., Murray, M., Krainer, A.R., Stalmans, W., Bollen, M. J. Biol. Chem. (2000) [Pubmed]
  14. Importance of the beta12-beta13 loop in protein phosphatase-1 catalytic subunit for inhibition by toxins and mammalian protein inhibitors. Connor, J.H., Kleeman, T., Barik, S., Honkanen, R.E., Shenolikar, S. J. Biol. Chem. (1999) [Pubmed]
  15. Interactor-mediated nuclear translocation and retention of protein phosphatase-1. Lesage, B., Beullens, M., Nuytten, M., Van Eynde, A., Keppens, S., Himpens, B., Bollen, M. J. Biol. Chem. (2004) [Pubmed]
  16. Phosphorylation-dependent interaction between the splicing factors SAP155 and NIPP1. Boudrez, A., Beullens, M., Waelkens, E., Stalmans, W., Bollen, M. J. Biol. Chem. (2002) [Pubmed]
  17. The C-terminus of NIPP1 (nuclear inhibitor of protein phosphatase-1) contains a novel binding site for protein phosphatase-1 that is controlled by tyrosine phosphorylation and RNA binding. Beullens, M., Vulsteke, V., Van Eynde, A., Jagiello, I., Stalmans, W., Bollen, M. Biochem. J. (2000) [Pubmed]
  18. The protein phosphatase-1 regulator NIPP1 is also a splicing factor involved in a late step of spliceosome assembly. Beullens, M., Bollen, M. J. Biol. Chem. (2002) [Pubmed]
  19. Alternatively spliced protein variants as potential therapeutic targets for male infertility and contraception. Fardilha, M., Wu, W., Sá, R., Fidalgo, S., Sousa, C., Mota, C., da Cruz e Silva, O.A., da Cruz e Silva, E.F. Ann. N. Y. Acad. Sci. (2004) [Pubmed]
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