PP1 regulatory subunit NIPP1 regulates transcription of E2F1 target genes following DNA damage.
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ABSTRACT:
SUBMITTER: Hanaki S
PROVIDER: S-EPMC8253265 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:BackgroundHow epithelial cells adopt their particular polarised forms is poorly understood. In a screen for genes regulating epithelial morphology in Drosophila, we identified sds22, a conserved gene previously characterised in yeast.ResultsIn the columnar epithelia of imaginal discs or follicle cells, mutation of sds22 causes contraction of cells along their apical-basal axis, resulting in a more cuboidal morphology. In addition, the mutant cells can also display altered cell polarity, forming multiple layers in follicle cells and leaving the epithelium in imaginal discs. In yeast, sds22 encodes a PP1 phosphatase regulatory subunit. Consistent with this, we show that Drosophila Sds22 binds to all four Drosophila PP1s and shares an overlapping phenotype with PP1beta9c. We also show that two previously postulated PP1 targets, Spaghetti Squash and Moesin are hyper-phosphorylated in sds22 mutants. This function is shared by the human homologue of Sds22, PPP1R7.ConclusionSds22 is a conserved PP1 phosphatase regulatory subunit that controls cell shape and polarity.
| S-EPMC2652452 | biostudies-literature
Project description:Electrical gradients are present in many developing and regenerating tissues and around tumours. Mimicking endogenous electric fields in vitro has profound effects on the behaviour of many cell types. Intriguingly, specific cell types migrate cathodally, others anodally and some polarise with their long axis perpendicular to the electric vector. These striking phenomena are likely to have in vivo relevance since one of the determining factors during cancer metastasis is the ability to switch between attractive and repulsive migration in response to extracellular guidance stimuli. We present evidence that the cervical cancer cell line HeLa migrates cathodally in a direct current electric field of physiological intensity, while the strongly metastatic prostate cancer cell line PC-3-M migrates anodally. Notably, genetic disruption of protein serine/threonine phosphatase-1 (PP1) and its regulator NIPP1 decrease directional migration in these cell lines. Conversely, the inducible expression of NIPP1 switched the directional response of HeLa cells from cathodal to slightly anodal in a PP1-dependent manner. Remarkably, induction of a hyperactive PP1/NIPP1 holoenzyme, further shifted directional migration towards the anode. We show that PP1 association with NIPP1 upregulates signalling by the GTPase Cdc42 and demonstrate that pharmacological inhibition of Cdc42 in cells overexpressing NIPP1 recovered cathodal migration. Taken together, we provide the first evidence for regulation of directional cell migration by NIPP1. In addition, we identify PP1/NIPP1 as a novel molecular compass that controls directed cell migration via upregulation of Cdc42 signalling and suggest a way by which PP1/NIPP1 may contribute to the migratory properties of cancer cells.
| S-EPMC3397927 | biostudies-literature
Project description:Regulation of protein phosphatase 1 (PP1) is controlled by a diverse array of regulatory proteins. However, how these proteins direct PP1 specificity is not well understood. More than one-third of the nuclear pool of PP1 forms a holoenzyme with the nuclear inhibitor of PP1, NIPP1, to regulate chromatin remodeling, among other essential biological functions. Here, we show that the PP1-binding domain of NIPP1 is an intrinsically disordered protein, which binds PP1 in an unexpected manner. NIPP1 forms an α helix that engages PP1 at a unique interaction site, using polar rather than hydrophobic contacts. Importantly, the structure also reveals a shared PP1 interaction site outside of the RVxF motif, the ΦΦ motif. Finally, we show that NIPP1:PP1 substrate selectivity is determined by altered electrostatics and enhanced substrate localization. Together, our results provide the molecular basis by which NIPP1 directs PP1 substrate specificity in the nucleus.
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Project description:Rif1 is a conserved protein that plays essential roles in orchestrating DNA replication timing, controlling nuclear architecture, telomere length and DNA repair. However, the relationship between these different roles, as well as the molecular basis of Rif1 function is still unclear. The association of Rif1 with insoluble nuclear lamina has thus far hampered exhaustive characterization of the associated protein complexes. We devised a protocol that overcomes this problem, and were thus able to discover a number of novel Rif1 interactors, involved in chromatin metabolism and phosphorylation. Among them, we focus here on PP1. Data from different systems have suggested that Rif1-PP1 interaction is conserved and has important biological roles. Using mutagenesis, NMR, isothermal calorimetry and surface plasmon resonance we demonstrate that Rif1 is a high-affinity PP1 adaptor, able to out-compete the well-established PP1-inhibitor I2 in vitro. Our conclusions have important implications for understanding Rif1 diverse roles and the relationship between the biological processes controlled by Rif1.
| S-EPMC5437018 | biostudies-literature
Project description:The catalytic subunit of type 1 Ser/Thr protein phosphatases (PP1c) forms complexes with many proteins that target it to particular subcellular locations and regulate its activity towards specific substrates. We report the identification of a Drosophila orthologue of nuclear inhibitor of PP1 (NIPP1Dm) through interaction with PP1c in the yeast two-hybrid system. NIPP1Dm shares many properties with mammalian NIPP1 including inhibition of PP1c in vitro, binding to RNA and PP1c, and localization to nuclear speckles. However, the mechanism controlling interaction of PP1c with NIPP1 is not conserved in Drosophila. NIPP1 can function independently of PP1c as a splicing factor, but the relative importance of this function is unknown. Over-expression of NIPP1Dm in Drosophila is cell-lethal in a range of tissues and developmental stages. The effects of ectopic NIPP1Dm are suppressed by co-expression of PP1c, indicating that the only effect of ectopic NIPP1Dm is to affect PP1c function. Co-expression of NIPP1Dm and PP1c does not have any detectable physiological effect in vivo, suggesting that the NIPP1Dm-PP1c holoenzyme is not normally limiting in Drosophila. These data show that NIPP1Dm and PP1c interact in vivo and suggest that NIPP1's role as a phosphatase regulator is conserved in Drosophila.
| S-EPMC1223049 | biostudies-literature
Project description:The deletion of the protein phosphatase-1 (PP1) regulator NIPP1 is embryonic lethal during gastrulation, hinting at a key role of PP1-NIPP1 in lineage specification. Consistent with this notion we show here that a mild, stable overexpression of NIPP1 in HeLa cells caused a massive induction of genes of the mesenchymal lineage, in particular smooth/cardiac-muscle and matrix markers. This reprogramming was associated with the formation of actin-based stress fibers and retracting filopodia, and a reduced proliferation potential. The NIPP1-induced mesenchymal transition required functional substrate and PP1-binding domains, suggesting that it involves the selective dephosphorylation of substrates of PP1-NIPP1.
2015-04-04 | GSE67558 | GEO
Project description:The deletion of the protein phosphatase-1 (PP1) regulator NIPP1 is embryonic lethal during gastrulation, hinting at a key role of PP1-NIPP1 in lineage specification. Consistent with this notion we show here that a mild, stable overexpression of NIPP1 in HeLa cells caused a massive induction of genes of the mesenchymal lineage, in particular smooth/cardiac-muscle and matrix markers. This reprogramming was associated with the formation of actin-based stress fibers and retracting filopodia, and a reduced proliferation potential. The NIPP1-induced mesenchymal transition required functional substrate and PP1-binding domains, suggesting that it involves the selective dephosphorylation of substrates of PP1-NIPP1. In total 16 samples were processed. Four different cell lines were analysed: HTO_parental, HTO_NIPP1wt, HTO_NIPP1m (= alias NIPP1-Pm) and HTO_NIPP1-Pa. For each cell line 4 replicates were obtained. The HTO_parental cell line is the control cell line. For the HTO_NIPP1wt and the HTO_NIPP1-Pa the 4 replicates were obtained from two replicates of two different transgenic cell lines expressing FlagNIPP1wt (cell line wt n°1 and 2) and FlagNIPP1-Pa (cell line n°1 and 2), respectively. Each cell line was derived from the same parental control cell line.
2015-04-04 | E-GEOD-67558 | biostudies-arrayexpress
Project description:NIPP1, an established interactor of protein phosphatase 1 (PP1), is implicated in PRC2-mediated regulation of gene expression. Here, we explore whether PP1 associated with NIPP1 is involved in NIPP1-mediated regulation of genes. Therefore, we generated Hela Tet-off (HTO) cell lines that stably and inducibly express a Flag-tagged version of wild-type NIPP1 (HTO-NIPP1wt) or mutant NIPP1 (HTO_NIPP1m). The latter mutant lacks the major PP1 binding site by two point mutations in the RVXF-motif, an established PP1 - binding motif. All cell lines were derived from the same parental HeLa Tet-Off (HTO-PT) cell line which expresses only tTA transactivator and is used as a control. The Flag fusions were only expressed in the absence of doxycyline and at levels that were up to twofold higher than that of endogenous NIPP1. We performed a gene expression profiling of the HTO cell lines, using Whole Human Genome Oligo microarrays from Agilent. A Paired SAM analysis identified 1365 genes with an altered expression (P < 0.01) between the Flag-NIPP1 and parental cell lines. Importantly, only 185 genes were differentially expressed (P<0.01) between the Flag-NIPP1m and parental cell lines. Even more strikingly, only 5% of the genes that were affected by the expression of Flag-NIPP1 also showed a significantly different expression in the Flag-NIPP1m cells. A similar small overlap was noted when the analysis was restricted to the 50 genes that were most upregulated or downregulated by the expression of Flag-NIPP1. Finally, scatter plot analysis revealed no significant correlation between the genes that were affected by the expression of Flag-NIPP1 or Flag-NIPP1m. Collectively, these data demonstrate that a moderate increase in the concentration of NIPP1 affects the expression of numerous genes by a mechanism that depends on associated PP1.
2010-07-19 | GSE19642 | GEO
Project description:Spermatogenesis is comprised of a series of highly regulated developmental changes that transform the precursor germ cell into a highly specialized spermatozoon. The last phase of spermatogenesis, termed spermiogenesis, involves dramatic morphological change including formation of the acrosome, elongation and condensation of the nucleus, formation of the flagella, and disposal of unnecessary cytoplasm. A prominent cytoskeletal component of the developing spermatid is the manchette, a unique microtubular structure that surrounds the nucleus of the developing spermatid and is thought to assist in both the reshaping of the nucleus and redistribution of spermatid cytoplasm. Although the molecular motor KIFC1 has been shown to associate with the manchette, its precise role in function of the manchette and the identity of its testis specific protein partners are unknown. The purpose of this study was to identify proteins in the testis that interact with KIFC1 using a yeast 2 hybrid screen of a testis cDNA library.Thirty percent of the interacting clones identified in our screen contain an identical cDNA encoding a 40 kD protein. This interacting protein has 4 leucine-rich repeats in its amino terminal half and is expressed primarily in the testis; therefore we have named this protein testis leucine-rich repeat protein or TLRR. TLRR was also found to associate tightly with the KIFC1 targeting domain using affinity chromatography. In addition to the leucine-rich repeats, TLRR contains a consensus-binding site for protein phosphatase-1 (PP1). Immunocytochemistry using a TLRR specific antibody demonstrates that this protein is found near the manchette of developing spermatids.We have identified a previously uncharacterized leucine-rich repeat protein that is expressed abundantly in the testis and associates with the manchette of developing spermatids, possibly through its interaction with the KIFC1 molecular motor. TLRR is homologous to a class of regulatory subunits for PP1, a central phosphatase in the reversible phosphorylation of proteins that is key to modulation of many intracellular processes. TLRR may serve to target this important signaling molecule near the nucleus of developing spermatids in order to control the cellular rearrangements of spermiogenesis.
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Project description:PTEN phosphorylation at its C-terminal (C-tail) serine/threonine cluster negatively regulates its tumor suppressor function. However, the consequence of such inhibition and its downstream effects in driving lung cancer remain unexplored. Herein, we ascertain the molecular mechanisms by which phosphorylation compromises PTEN function, contributing to lung cancer. Replacement of the serine/threonine residues with alanine generated PTEN-4A, a phosphorylation-deficient PTEN mutant, which suppressed lung cancer cell proliferation and migration. PTEN-4A preferentially localized to the nucleus where it suppressed E2F1-mediated transcription of cell cycle genes. PTEN-4A physically interacted with the transcription factor E2F1 and associated with chromatin at gene promoters with E2F1 DNA-binding sites, a likely mechanism for its transcriptional suppression function. Deletion analysis revealed that the C2 domain of PTEN was indispensable for suppression of E2F1-mediated transcription. Further, we uncovered cancer-associated C2 domain mutant proteins that had lost their ability to suppress E2F1-mediated transcription, supporting the concept that these mutations are oncogenic in patients. Consistent with these findings, we observed increased PTEN phosphorylation and reduced nuclear PTEN levels in lung cancer patient samples establishing phosphorylation as a bona fide inactivation mechanism for PTEN in lung cancer. Thus, use of small molecule inhibitors that hinder PTEN phosphorylation is a plausible approach to activate PTEN function in the treatment of lung cancer. Abbreviations AKT V-Akt Murine Thymoma Viral Oncogene CA Cancer adjacent CDK1 Cyclin dependent kinase 1 CENPC-C Centromere Protein C ChIP Chromatin Immunoprecipitation co-IP Co-immunoprecipitation COSMIC Catalog of Somatic Mutations In Cancer CREB cAMP Responsive Element Binding Protein C-tail Carboxy terminal tail E2F1 E2F Transcription Factor 1 ECIS Electric Cell-substrate Impedance Sensing EGFR Epidermal Growth Factor Receptor GSI Gamma Secretase Inhibitor HDAC1 Histone Deacetylase 1 HP1 Heterochromatin protein 1 KAP1/TRIM28 KRAB-Associated Protein 1/Tripartite Motif Containing 28 MAF1 Repressor of RNA polymerase III transcription MAF1 homolog MCM2 Minichromosome Maintenance Complex Component 2 miRNA micro RNA MTF1 Metal-Regulatory Transcription Factor 1 PARP Poly(ADP-Ribose) Polymerase PD-1 Programmed Cell Death 1 PD-L1 Programmed Cell Death 1 Ligand 1 PI3K Phosphatidylinositol-4,5-Bisphosphate 3-Kinase PLK Polo-like Kinase pPTEN Phosphorylated PTEN PTEN Phosphatase and Tensin Homolog deleted on chromosome ten PTM Post Translational Modification Rad51 RAD51 Recombinase Rad52 RAD52 Recombinase RPA1 Replication protein A SILAC Stable Isotope Labeling with Amino Acids in Cell Culture SRF Serum Response Factor TKI Tyrosine Kinase inhbitors TMA Tissue Microarray TOP2A DNA Topoisomerase 2A.
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