Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.1 (protein kinase)
 81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

NIPP-1 was originally isolated as a potent and specific nuclear inhibitory polypeptide (16-18 kDa) of protein phosphatase-1. We report here the cDNA cloning of NIPP-1 from bovine thymus and show that the native polypeptide consists of 351 residues and has a calculated mass of 38.5 kDa. The bacterially expressed central third of NIPP-1 completely inhibited the type-1 catalytic subunit, but displayed a reduced inhibitory potency after phosphorylation by protein kinase A and casein kinase 2. 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. A data base search showed that the COOH terminus of NIPP-1 is nearly identical to the human ard-1 protein (13 kDa), which has been implicated in RNA processing (Wang, M., and Cohen, S. N. (1994) Proc. Natl. Acad. Sci. U. S. A. 91, 10591-10595). Comparison of the cDNAs encoding ard-1 and NIPP-1 suggests that their mRNAs are generated by alternative splicing of the same pre-mRNA. 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. Northern analysis revealed a single transcript of 2.2 kilobases in bovine thymus and of 2.4 kilobases in various human tissues.
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PMID:Molecular cloning of NIPP-1, a nuclear inhibitor of protein phosphatase-1, reveals homology with polypeptides involved in RNA processing. 749 93

The activity of protein phosphatase-1 in rat liver nuclei (PP-1N) was decreased by up to 97% by associated inhibitory polypeptides, depending on the assay and extraction conditions. These inhibitors were rapidly degraded by endogenous proteases, resulting in the accumulation of active heat-stable intermediates. Two major species of PP-1N could be differentiated by fractionation of a nuclear extract. PP-1NR111 contained, besides the delta-isoform of the catalytic subunit, an inhibitory polypeptide of 111 kDa. PP-1NR41 was found to be an inactive heterodimer between the delta-isoform of the catalytic subunit and NIPP-1, a nuclear inhibitor of PP-1, which in its undegraded form is heat labile and migrates during SDS-polyacrylamide gel electrophoresis as a polypeptide of 41 kDa. Native hepatic NIPP-1 displayed a reduced affinity for the catalytic subunit after phosphorylation by protein kinase A in vitro and after glucagon-induced phosphorylation in vivo.
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PMID:Subunit structure and regulation of protein phosphatase-1 in rat liver nuclei. 761 25

Bovine thymus nuclei contain a species of protein phosphatase-1 (PP-1N alpha) that can be partially activated by phosphorylation of an associated inhibitory polypeptide, NIPP-1, with protein kinase A [Beullens, Van Eynde, Bollen and Stalmans (1993) J. Biol. Chem. 268, 13172-13177]. Here it is shown that PP-1N alpha can also be activated 4-fold by phosphorylation of NIPP-1 with casein kinase-2. The effects of protein kinase A and casein kinase-2 were additive, yielding an enzyme with an activity close to that of the free catalytic subunit. Casein kinase-2 introduced up to 1.2 phosphate groups into purified NIPP-1 on serine and threonine residues. This phosphorylation was associated with a 14-fold increase in the concentration of NIPP-1 required for 50% inhibition of the type-1 catalytic subunit. The kinase-mediated inactivation of NIPP-1 could be reversed by incubation with the catalytic subunit of protein phosphatase-2A.
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PMID:Full activation of a nuclear species of protein phosphatase-1 by phosphorylation with protein kinase A and casein kinase-2. 811 Jan 79

We have recently purified two potent and specific inhibitory polypeptides of protein phosphatase-1 from the particulate fraction of bovine thymus nuclei (Beullens, M., Van Eynde, A., Stalmans, W., and Bollen, M. (1992) J. Biol. Chem. 267, 16538-16544). Here it is reported that these inhibitors, termed NIPP-1a (18 kDa) and NIPP-1b (16 kDa), are excellent substrates (Km = 0.1 microM) for phosphorylation by protein kinase A on both Ser and Thr residues. Phosphorylation was temporally closely related with an activation of NIPP-1. Maximal phosphorylation by protein kinase A (1.5 mol of phosphate/mol of NIPP-1) caused an 8-fold increase in the concentration of NIPP-1 required for half-complete inhibition of the catalytic subunit of protein phosphatase-1, irrespective of the concentration of the phosphatase. Phosphorylation decreased the binding of NIPP-1 to immobilized protein phosphatase-1. NIPP-1 could be efficiently and completely reactivated by incubation with the catalytic subunit of protein phosphatase-2A. The type-1 catalytic subunit was much less effective, however, even when present in a molar excess to NIPP-1. Chromatography of a salt extract of the particulate nuclear fraction of Mono Q revealed three species of PP-1. One of these species, termed PP-1N alpha, contained NIPP-1 as a subunit and could be activated 6-fold by incubation with protein kinase A under phosphorylating conditions. This activation of PP-1N alpha is opposite to the known inhibition of cytoplasmic species of protein phosphatase-1 by protein kinase A.
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PMID:Inactivation of nuclear inhibitory polypeptides of protein phosphatase-1 (NIPP-1) by protein kinase A. 839 Apr 58

In this study we demonstrate that recombinant rabbit muscle protein phosphatase-1 immobilized on CH-Sepharose is an efficient affinity chromatography support for the isolation of subunits of phosphatase-1. The support was used to isolate the glycogen binding subunit of phosphatase-1 from muscle and nonmuscle rat tissues. Examination of the affinity-purified material from rat heart and liver showed that the major component was a 160-kDa polypeptide on SDS-PAGE. The identity of the purified liver 160-kDa polypeptide as the glycogen binding subunit was confirmed by the demonstration that it is capable of binding to glycogen, and is phosphorylated by the catalytic subunit of PKA. The novel observation was made that the phosphorylation was dependent on the presence of glycogen. Examination of the material from heart, lung, liver, kidney, and brain showed a similar phenomenon. Our studies show that this subunit is widely distributed in tissues. The affinity support was also efficient in the isolation of the NIPP-1 (nuclear inhibitor of protein phosphatase-1) proteins from calf thymus. Examination of heat-treated extracts of rat liver led to the isolation of a novel 19-kDa inhibitory protein which could also be phosphorylated by PKA and may represent the rat liver homolog of calf thymus NIPP-1.
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PMID:Affinity chromatography of regulatory subunits of protein phosphatase-1. 855 47

NIPP-1 is a nuclear inhibitory subunit of protein phosphatase-1 with structural similarities to some proteins involved in RNA processing. We report here that baculovirus-expressed recombinant NIPP-1 displays RNA-binding properties, as revealed by North-Western analysis, by UV-mediated cross-linking, by RNA mobility-shift assays, and by chromatography on poly(U)-Sepharose. NIPP-1 preferentially bound to U-rich sequences, including RNA-destabilizing AUUUA motifs. NIPP-1 also associated with single-stranded DNA, but had no affinity for double-stranded DNA. The binding of NIPP-1 to RNA was blocked by antibodies directed against the COOH terminus of NIPP-1, but was not affected by prior phosphorylation of NIPP-1 with protein kinase A or casein kinase-2, which decreases the affinity of NIPP-1 for protein phosphatase-1. The catalytic subunit of protein phosphatase-1 did not bind to poly(U)-Sepharose, but it bound very tightly after complexation with NIPP-1. These data are in agreement with a function of NIPP-1 in targeting protein phosphatase-1 to RNA.
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PMID:NIPP-1, a nuclear inhibitory subunit of protein phosphatase-1, has RNA-binding properties. 926 47

NIPP-1 is a subunit of the major nuclear protein phosphatase-1 (PP-1) in mammalian cells and potently inhibits PP-1 activity in vitro. Using yeast two-hybrid and co-sedimentation assays, we mapped a PP-1-binding site and the inhibition function to the central one-third domain of NIPP-1. Full-length NIPP-1 (351 residues) and the central domain, NIPP-1(143-217), were equally potent PP-1 inhibitors (IC50 = 0.3 nM). Synthetic peptides spanning the central domain of NIPP-1 further narrowed the PP-1 inhibitory function to residues 191-200. A second, noninhibitory PP-1-binding site was identified by far-Western assays with digoxygenin-conjugated catalytic subunit (PP-1C) and included a consensus RVXF motif (residues 200-203) found in many other PP-1-binding proteins. The substitutions, V201A and/or F203A, in the RVXF motif, or phosphorylation of Ser199 or Ser204, which are established phosphorylation sites for protein kinase A and protein kinase CK2, respectively, prevented PP-1C-binding by NIPP-1(191-210) in the far-Western assay. NIPP-1(191-210) competed for PP-1 inhibition by full-length NIPP-1(1-351), inhibitor-1 and inhibitor-2, and dissociated PP-1C from inhibitor-1- and NIPP-1(143-217)-Sepharose but not from full-length NIPP-1(1-351)-Sepharose. Together, these data identified some of the key elements in the central domain of NIPP-1 that regulate PP-1 activity and suggested that the flanking sequences stabilize the association of NIPP-1 with PP-1C.
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PMID:Molecular determinants of nuclear protein phosphatase-1 regulation by NIPP-1. 1031 19

NIPP1 (nuclear inhibitor of protein phosphatase 1) is a ubiquitously expressed nuclear scaffold protein that has been implicated in both transcription and RNA processing. Among its protein ligands are a protein kinase, a protein phosphatase, two splicing factors, and a transcriptional regulator, and the binding of these proteins to NIPP1 is tightly regulated by phosphorylation. To study the function of NIPP1 in vivo, we have used homologous recombination to generate mice that are deficient in NIPP1. NIPP1(-/+) mice developed normally. However, NIPP1(-/-) embryos showed severely retarded growth at embryonic day 6.5 (E6.5) and were resorbed by E8.5. This early embryonic lethality was not associated with increased apoptosis but correlated with impaired cell proliferation. Blastocyst outgrowth experiments and the RNA interference-mediated knockdown of NIPP1 in cultured cells also revealed an essential role for NIPP1 in cell proliferation. In further agreement with this function, no viable NIPP1(-/-) cell lines were obtained by derivation of embryonic stem (ES) cells from blastocysts of NIPP1(-/+) intercrosses or by forced homogenotization of heterozygous ES cells at high concentrations of Geneticin. We conclude that NIPP1 is indispensable for early embryonic development and cell proliferation.
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PMID:The nuclear scaffold protein NIPP1 is essential for early embryonic development and cell proliferation. 1519 42

The cyclin-dependent kinase CDK9/cyclin T1 induces HIV-1 transcription by phosphorylating the carboxyterminal domain (CTD) of RNA polymerase II (RNAPII). CDK9 activity is regulated by protein phosphatase-1 (PP1) which was previously shown to dephosphorylate CDK9 Thr186. Here, we analyzed the effect of PP1 on RNAPII phosphorylation and CDK9 activity. The selective inhibition of PP1 by okadaic acid and by NIPP1 inhibited phosphorylation of RNAPII CTD in vitro and in vivo. Expression of the central domain of NIPP1 in cultured cells inhibited the enzymatic activity of CDK9 suggesting its activation by PP1. Comparison of dephosphorylation of CDK9 phosphorylated by ((32)P) in vivo and dephosphorylation of CDK9's Thr186 analyzed by Thr186 phospho-specific antibodies, indicated that a residue other than Thr186 might be dephosphorylated by PP1. Analysis of dephosphorylation of phosphorylated peptides derived from CDK9's T-loop suggested that PP1 dephosphorylates CDK9 Ser175. In cultured cells, CDK9 was found to be phosphorylated on Ser175 as determined by combination of Hunter 2D peptide mapping and LC-MS analysis. CDK9 S175A mutant was active and S175D--inactive, and dephosphorylation of CDK9's Ser175 upregulated HIV-1 transcription in PP1-dependent manner. Collectively, our results point to CDK9 Ser175 as novel PP1-regulatory site which dephosphorylation upregulates CDK9 activity and contribute to the activation of HIV-1 transcription.
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PMID:Protein phosphatase-1 activates CDK9 by dephosphorylating Ser175. 2153 37