scholarly journals Cdk2 and Pin1 negatively regulate the transcriptional corepressor SMRT

2008 ◽  
Vol 183 (1) ◽  
pp. 49-61 ◽  
Author(s):  
Kristopher J. Stanya ◽  
Yu Liu ◽  
Anthony R. Means ◽  
Hung-Ying Kao
Keyword(s):  
Transcriptional Repression ◽  
Mammalian Cells ◽  
Cellular Response ◽  
Thyroid Hormone Receptor ◽  
Signaling Cascade ◽  
Phosphorylation Sites ◽  
Transcriptional Corepressor ◽  
Prolyl Isomerase ◽  
Peptidyl Prolyl Isomerase

Silencing mediator for retinoic acid and thyroid hormone receptor (SMRT) is a transcriptional corepressor that participates in diverse signaling pathways and human diseases. However, regulation of SMRT stability remains largely unexplored. We show that the peptidyl-prolyl isomerase Pin1 interacts with SMRT both in vitro and in mammalian cells. This interaction requires the WW domain of Pin1 and SMRT phosphorylation. Pin1 regulates SMRT protein stability, thereby affecting SMRT-dependent transcriptional repression. SMRT phosphorylation at multiple sites is required for Pin1 interaction, and these sites can be phosphorylated by Cdk2, which interacts with SMRT. Cdk2-mediated phosphorylation of SMRT is required for Pin1 binding and decreases SMRT stability, whereas mutation of these phosphorylation sites abrogates Pin1 binding and stabilizes SMRT. Finally, decreases in SMRT stability occur in response to the activation of Her2/Neu/ErbB2, and this receptor functions upstream of both Pin1 and Cdk2 in the signaling cascade that regulates SMRT stability and cellular response to tamoxifen.

scholarly journals The Role of PPARγin the Transcriptional Control by Agonists and Antagonists

PPAR Research ◽  
2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Tamotsu Tsukahara
Keyword(s):  
Transcriptional Repression ◽  
Transcriptional Control ◽  
Thyroid Hormone Receptor ◽  
Therapeutic Potential ◽  
Current Knowledge ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Cyclic Phosphatidic Acid

In recent years, peroxisome proliferator-activated receptor gamma (PPARγ) has been reported to be a target for the treatment of type II diabetes. Furthermore, it has received attention for its therapeutic potential in many other human diseases, including atherosclerosis, obesity, and cancers. Recent studies have provided evidence that the endogenously produced PPARγ antagonist, 2,3-cyclic phosphatidic acid (cPA), which is similar in structure to lysophosphatidic acid (LPA), inhibits cancer cell invasion and metastasisin vitroandin vivo. We recently observed that cPA negatively regulates PPARγ function by stabilizing the binding of the corepressor protein, silencing mediator of retinoic acid and thyroid hormone receptor. We also showed that cPA prevents neointima formation, adipocyte differentiation, lipid accumulation, and upregulation of PPARγ target gene transcription. We then analyzed the molecular mechanism of cPA's action on PPARγ. In this paper, we summarize the current knowledge on the mechanism of PPARγ-mediated transcriptional activity and transcriptional repression in response to novel lipid-derived ligands, such as cPA.

scholarly journals A feedback transcriptional mechanism controls the level of the arginine/lysine transporter cat-1 during amino acid starvation

2007 ◽  
Vol 402 (1) ◽  
pp. 163-173 ◽  
Author(s):  
Alex B. Lopez ◽  
Chuanping Wang ◽  
Charlie C. Huang ◽  
Ibrahim Yaman ◽  
Yi Li ◽  
...  
Keyword(s):  
Amino Acid ◽  
Transcriptional Activation ◽  
Transcriptional Repression ◽  
Mammalian Cells ◽  
Leucine Zipper ◽  
Amino Acid Starvation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Basic Leucine Zipper

The adaptive response to amino acid limitation in mammalian cells inhibits global protein synthesis and promotes the expression of proteins that protect cells from stress. The arginine/lysine transporter, cat-1, is induced during amino acid starvation by transcriptional and post-transcriptional mechanisms. It is shown in the present study that the transient induction of cat-1 transcription is regulated by the stress response pathway that involves phosphorylation of the translation initiation factor, eIF2 (eukaryotic initiation factor-2). This phosphorylation induces expression of the bZIP (basic leucine zipper protein) transcription factors C/EBP (CCAAT/enhancer-binding protein)-β and ATF (activating transcription factor) 4, which in turn induces ATF3. Transfection experiments in control and mutant cells, and chromatin immunoprecipitations showed that ATF4 activates, whereas ATF3 represses cat-1 transcription, via an AARE (amino acid response element), TGATGAAAC, in the first exon of the cat-1 gene, which functions both in the endogenous and in a heterologous promoter. ATF4 and C/EBPβ activated transcription when expressed in transfected cells and they bound as heterodimers to the AARE in vitro. The induction of transcription by ATF4 was inhibited by ATF3, which also bound to the AARE as a heterodimer with C/EBPβ. These results suggest that the transient increase in cat-1 transcription is due to transcriptional activation caused by ATF4 followed by transcriptional repression by ATF3 via a feedback mechanism.

Dose Patterns of Cellular Effects Induced by Carcinogens: Evidence for the Presence or Absence of Thresholds

1983 ◽  
Vol 2 (3) ◽  
pp. 185-193
Author(s):  
Jerry R. Williams ◽  
Peter D'Arpa
Keyword(s):  
Mammalian Cells ◽  
Cellular Response ◽  
Response Curve ◽  
Human Populations ◽  
Low Doses ◽  
Human Beings ◽  
Environmental Carcinogens ◽  
Cellular Effects ◽  
Cancer Induction

The patterns of response of individual cells to carcinogens may be a factor that influences the shape of the dose-response curve for cancer in human populations; thus the existence of a threshold for cellular response may imply a threshold for cancer induction. The patterns of response of cultured mammalian cells to carcinogen treatment is described for four cellular endpoints: cytotoxidty, mutation, sister chromatid exchange, and in vitro transformation. These data, taken in toto, indicate that for some carcinogens a threshold exists for the induction of cellular effects, but for some carcinogens thresholds probably do not exist. Cancer-prone human beings may contain cell populations without thresholds, making them especially sensitive to low doses of environmental carcinogens.

scholarly journals Noncatalytic Role of the FKBP52 Peptidyl-Prolyl Isomerase Domain in the Regulation of Steroid Hormone Signaling

2007 ◽  
Vol 27 (24) ◽  
pp. 8658-8669 ◽  
Author(s):  
Daniel L. Riggs ◽  
Marc B. Cox ◽  
Heather L. Tardif ◽  
Martin Hessling ◽  
Johannes Buchner ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Hormone Receptors ◽  
Steroid Hormone ◽  
Genetic Selection ◽  
Steroid Hormone Receptors ◽  
Hormone Signaling ◽  
Prolyl Isomerase ◽  
Peptidyl Prolyl Isomerase ◽  
Isomerase Activity ◽  
Steroid Hormone Signaling

ABSTRACT Hormone-dependent transactivation by several of the steroid hormone receptors is potentiated by the Hsp90-associated cochaperone FKBP52, although not by the closely related FKBP51. Here we analyze the mechanisms of potentiation and the functional differences between FKBP51 and FKBP52. While both have peptidyl-prolyl isomerase activity, this is not required for potentiation, as mutations abolishing isomerase activity did not affect potentiation. Genetic selection in Saccharomyces cerevisiae for gain of potentiation activity in a library of randomly mutated FKBP51 genes identified a single residue at position 119 in the N-terminal FK1 domain as being a critical difference between these two proteins. In both the yeast model and mammalian cells, the FKBP51 mutation L119P, which is located in a hairpin loop overhanging the catalytic pocket and introduces the proline found in FKBP52, conferred significant potentiation activity, whereas the converse P119L mutation in FKBP52 decreased potentiation. A second residue in this loop, A116, also influences potentiation levels; in fact, the FKBP51-A116V L119P double mutant potentiated hormone signaling as well as wild-type FKBP52 did. These results suggest that the FK1 domain, and in particular the loop overhanging the catalytic pocket, is critically involved in receptor interactions and receptor activity.

scholarly journals Phosphorylation of ORF1p is required for L1 retrotransposition

2015 ◽  
Vol 112 (14) ◽  
pp. 4298-4303 ◽  
Author(s):  
Pamela R. Cook ◽  
Charles E. Jones ◽  
Anthony V. Furano
Keyword(s):  
Specific Interaction ◽  
Biochemical Property ◽  
Prolyl Isomerase ◽  
Peptidyl Prolyl Isomerase ◽  
Cyclin Dependent Kinases ◽  
Host Interaction ◽  
Mitogen Activated Protein ◽  
Regulatory Cascades ◽  
Substrate Conformation

Although members of the L1 (LINE-1) clade of non-LTR retrotransposons can be deleterious, the L1 clade has remained active in most mammals for ∼100 million years and generated almost 40% of the human genome. The details of L1–host interaction are largely unknown, however. Here we report that L1 activity requires phosphorylation of the protein encoded by the L1 ORF1 (ORF1p). Critical phospho-acceptor residues (two serines and two threonines) reside in four conserved proline-directed protein kinase (PDPK) target sites. The PDPK family includes mitogen-activated protein kinases and cyclin-dependent kinases. Mutation of any PDPK phospho-acceptor inhibits L1 retrotransposition. The phosphomimetic aspartic acid can restore activity at the two serine sites, but not at either threonine site, where it is strongly inhibitory. ORF1p also contains conserved PDPK docking sites, which promote specific interaction of PDPKs with their targets. As expected, mutations in these sites also inhibit L1 activity. PDPK mutations in ORF1p that inactivate L1 have no significant effect on the ability of ORF1p to anneal RNA in vitro, an important biochemical property of the protein. We show that phosphorylated PDPK sites in ORF1p are required for an interaction with the peptidyl prolyl isomerase 1 (Pin1), a critical component of PDPK-mediated regulation. Pin1 acts via isomerization of proline side chains at phosphorylated PDPK motifs, thereby affecting substrate conformation and activity. Our demonstration that L1 activity is dependent on and integrated with cellular phosphorylation regulatory cascades significantly increases our understanding of interactions between L1 and its host.

scholarly journals Cyclophilin D regulates necrosis, but not apoptosis, of murine eosinophils

2016 ◽  
Vol 310 (8) ◽  
pp. G609-G617 ◽  
Author(s):  
Xiang Zhu ◽  
Simon P. Hogan ◽  
Jeffery D. Molkentin ◽  
Nives Zimmermann
Keyword(s):  
Apoptotic Cell ◽  
Cyclophilin D ◽  
Prolyl Isomerase ◽  
Peptidyl Prolyl Isomerase ◽  
Significant Difference ◽  
Insight Into ◽  
Colitis Model ◽  
Eosinophil Degranulation

Eosinophil degranulation and clusters of free extracellular granules are frequently observed in diverse diseases, including atopic dermatitis, nasal polyposis, and eosinophilic esophagitis. Whether these intact granules are released by necrosis or a biochemically mediated cytolysis remains unknown. Recently, a peptidyl-prolyl isomerase located within the mitochondrial matrix, cyclophilin D (PPIF), was shown to regulate necrotic, but not apoptotic, cell death in vitro in fibroblasts, hepatocytes, and cardiomyocytes. Whether cyclophilin D regulates necrosis in hematopoietic cells such as eosinophils remains unknown. We used PPIF-deficient ( Ppif−/−) mice to test whether cyclophilin D is required for regulating eosinophil necrosis. PPIF deficiency did not affect eosinophil development or maturation at baseline. After in vitro ionomycin or H2O2 treatment, Ppif−/− eosinophils were significantly protected from Ca2+ overload- or oxidative stress-induced necrosis. Additionally, Ppif−/− eosinophils demonstrated significantly decreased necrosis, but not apoptosis, in response to Siglec-F cross-linking, a stimulus associated with eosinophil-mediated processes in vitro and in vivo. When treated with apoptosis inducers, Ppif+/+ and Ppif−/− eosinophils exhibited no significant difference in apoptosis or secondary necrosis. Finally, in a dextran sodium sulfate-induced colitis model, although levels of colitogenic cytokines and eosinophil-selective chemokines were comparable between Ppif+/+ and Ppif−/− mice, the latter exhibited decreased clinical outcomes. This correlated with significantly reduced eosinophil cytolysis in the colon. Collectively, our present studies demonstrate that murine eosinophil necrosis is regulated in vitro and in vivo by cyclophilin D, at least in part, thus providing new insight into the mechanism of eosinophil necrosis and release of free extracellular granules in eosinophil-associated diseases.

scholarly journals Unliganded thyroid hormone receptor alpha can target TATA-binding protein for transcriptional repression.

1996 ◽  
Vol 16 (1) ◽  
pp. 281-287 ◽  
Author(s):  
J D Fondell ◽  
F Brunel ◽  
K Hisatake ◽  
R G Roeder
Keyword(s):  
Thyroid Hormone ◽  
Hormone Receptor ◽  
Transcriptional Repression ◽  
Thyroid Hormone Receptor ◽  
Binding Protein ◽  
Tata Binding Protein ◽  
Human Thyroid ◽  
Terminal Ligand ◽  
Receptor Alpha

Unliganded human thyroid hormone receptor alpha (hTR alpha) can repress transcription by inhibiting the formation of a functional preinitiation complex (PIC) on promoters bearing thyroid hormone receptor (TR)-binding elements. Here we demonstrate that hTR alpha directly contacts the TATA-binding protein (TBP) and that preincubation of hTR alpha with TBP completely alleviates TR-mediated repression in vitro. Using stepwise preassembled PICs, we show that hTR alpha targets either the TBP/TFIIA or the TBP/TFIIA/TFIIB steps of PIC assembly for repression. We also show that the repression domain of hTR alpha maps to the C-terminal ligand-binding region and that direct TR-TBP interactions can be inhibited by thyroid hormone. Together, these results suggest a model in which unliganded hTR alpha contacts promoter-bound TBP and interferes with later steps in the initiation of transcription.

scholarly journals SRPK2: A Differentially Expressed SR Protein-specific Kinase Involved in Mediating the Interaction and Localization of Pre-mRNA Splicing Factors in Mammalian Cells

1998 ◽  
Vol 140 (4) ◽  
pp. 737-750 ◽  
Author(s):  
Huan-You Wang ◽  
Wen Lin ◽  
Jacqueline A. Dyck ◽  
Joanne M. Yeakley ◽  
Zhou Songyang ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Mrna Splicing ◽  
Splicing Factors ◽  
Splicing Regulation ◽  
Phosphorylation Sites ◽  
Sr Protein ◽  
Random Peptide ◽  
Selection For

Abstract. Reversible phosphorylation plays an important role in pre-mRNA splicing in mammalian cells. Two kinases, SR protein-specific kinase (SRPK1) and Clk/Sty, have been shown to phosphorylate the SR family of splicing factors. We report here the cloning and characterization of SRPK2, which is highly related to SRPK1 in sequence, kinase activity, and substrate specificity. Random peptide selection for preferred phosphorylation sites revealed a stringent preference of SRPK2 for SR dipeptides, and the consensus derived may be used to predict potential phosphorylation sites in candidate arginine and serine-rich (RS) domain–containing proteins. Phosphorylation of an SR protein (ASF/SF2) by either SRPK1 or 2 enhanced its interaction with another RS domain–containing protein (U1 70K), and overexpression of either kinase induced specific redistribution of splicing factors in the nucleus. These observations likely reflect the function of the SRPK family of kinases in spliceosome assembly and in mediating the trafficking of splicing factors in mammalian cells. The biochemical and functional similarities between SRPK1 and 2, however, are in contrast to their differences in expression. SRPK1 is highly expressed in pancreas, whereas SRPK2 is highly expressed in brain, although both are coexpressed in other human tissues and in many experimental cell lines. Interestingly, SRPK2 also contains a proline-rich sequence at its NH2 terminus, and a recent study showed that this NH2-terminal sequence has the capacity to interact with a WW domain protein in vitro. Together, our studies suggest that different SRPK family members may be uniquely regulated and targeted, thereby contributing to splicing regulation in different tissues, during development, or in response to signaling.

scholarly journals ICBP90, a Novel Methyl K9 H3 Binding Protein Linking Protein Ubiquitination with Heterochromatin Formation

2007 ◽  
Vol 28 (2) ◽  
pp. 705-717 ◽  
Author(s):  
Panagiota Karagianni ◽  
Larbi Amazit ◽  
Jun Qin ◽  
Jiemin Wong
Keyword(s):  
Transcriptional Repression ◽  
Mammalian Cells ◽  
Specific Binding ◽  
Binding Protein ◽  
Biological Effects ◽  
Binding Activity ◽  
Effector Proteins ◽  
Heterochromatin Formation ◽  
Protein Ubiquitination

ABSTRACT Methylation of histone H3 on lysine 9 is critical for diverse biological processes including transcriptional repression, heterochromatin formation, and X inactivation. The biological effects of histone methylation are thought to be mediated by effector proteins that recognize and bind to specific patterns of methylation. Using an unbiased in vitro biochemical approach, we have identified ICBP90, a transcription and cell cycle regulator, as a novel methyl K9 H3-specific binding protein. ICBP90 and its murine homologue Np95 are enriched in pericentric heterochromatin of interphase nuclei, and this localization is dependent on H3K9 methylation. Specific binding of ICBP90 to methyl K9 H3 depends on two functional domains, a PHD (plant homeodomain) finger that defines the binding specificity and an SRA (SET- and RING-associated) domain that promotes binding activity. Furthermore, we present evidence that ICBP90 is required for proper heterochromatin formation in mammalian cells.

scholarly journals The Peptidyl-Prolyl Isomerase Activity of SlyD Is Not Required for Maturation of Escherichia coli Hydrogenase

2007 ◽  
Vol 189 (21) ◽  
pp. 7942-7944 ◽  
Author(s):  
Jie Wei Zhang ◽  
Michael R. Leach ◽  
Deborah B. Zamble
Keyword(s):  
Escherichia Coli ◽  
Metal Cluster ◽  
The Other ◽  
Prolyl Isomerase ◽  
Ppiase Activity ◽  
Peptidyl Prolyl Isomerase ◽  
Isomerase Activity ◽  
Hydrogenase Enzymes

ABSTRACT Escherichia coli SlyD, which is involved in the biosynthesis of the metal cluster in the [NiFe]-hydrogenase enzymes, exhibits several activities including that of a peptidyl-prolyl isomerase (PPIase). Mutations that result in deficient PPIase activity do not produce corresponding decreases in the other activities of SlyD in vitro or in hydrogenase production levels in vivo.

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