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Tan S, Sagara Y, Liu Y, Maher P, Schubert D. The regulation of reactive oxygen species production during programmed cell death. J Cell Biol 1998; 141:1423-32. [PMID: 9628898 PMCID: PMC2132785 DOI: 10.1083/jcb.141.6.1423] [Citation(s) in RCA: 600] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 01/08/1998] [Revised: 05/04/1998] [Indexed: 02/07/2023] Open
Abstract
Reactive oxygen species (ROS) are thought to be involved in many forms of programmed cell death. The role of ROS in cell death caused by oxidative glutamate toxicity was studied in an immortalized mouse hippocampal cell line (HT22). The causal relationship between ROS production and glutathione (GSH) levels, gene expression, caspase activity, and cytosolic Ca2+ concentration was examined. An initial 5-10-fold increase in ROS after glutamate addition is temporally correlated with GSH depletion. This early increase is followed by an explosive burst of ROS production to 200-400-fold above control values. The source of this burst is the mitochondrial electron transport chain, while only 5-10% of the maximum ROS production is caused by GSH depletion. Macromolecular synthesis inhibitors as well as Ac-YVAD-cmk, an interleukin 1beta-converting enzyme protease inhibitor, block the late burst of ROS production and protect HT22 cells from glutamate toxicity when added early in the death program. Inhibition of intracellular Ca2+ cycling and the influx of extracellular Ca2+ also blocks maximum ROS production and protects the cells. The conclusion is that GSH depletion is not sufficient to cause the maximal mitochondrial ROS production, and that there is an early requirement for protease activation, changes in gene expression, and a late requirement for Ca2+ mobilization.
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Arraud N, Linares R, Tan S, Gounou C, Pasquet JM, Mornet S, Brisson AR. Extracellular vesicles from blood plasma: determination of their morphology, size, phenotype and concentration. J Thromb Haemost 2014; 12:614-27. [PMID: 24618123 DOI: 10.1111/jth.12554] [Citation(s) in RCA: 551] [Impact Index Per Article: 50.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 12/07/2013] [Accepted: 03/04/2014] [Indexed: 12/15/2022]
Abstract
BACKGROUND Plasma and other body fluids contain membranous extracellular vesicles (EVs), which are considered to derive from activated or apoptotic cells. EVs participate in physiological and pathological processes and have potential applications in diagnostics or therapeutics. Knowledge on EVs is, however, limited, mainly due to their sub-micrometer size and to intrinsic limitations in methods applied for their characterization. OBJECTIVES Our aim was to provide a comprehensive description of EVs from plasma of healthy subjects. METHODS Cryo-transmission electron microscopy combined with receptor-specific gold labeling was used to reveal the morphology, size and phenotype of EVs. An original approach based on sedimentation on electron microscopy grids was developed for enumerating EVs. A correlation was performed between conventional flow cytometry and electron microscopy results. RESULTS We show that platelet-free plasma samples contain spherical EVs, 30 nm to 1 μm in diameter, tubular EVs, 1-5 μm long, and membrane fragments, 1-8 μm large. We show that only a minority of EVs expose the procoagulant lipid phosphatidylserine, in contrast to the classical theory of EV formation. In addition, the concentrations of the main EV sub-populations are determined after sedimentation on EM grids. Finally, we show that conventional flow cytometry, the main method of EV characterization, detects only about 1% of them. CONCLUSION This study brings novel insights on EVs from normal plasma and provides a reference for further studies of EVs in disease situations.
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Kelly S, Jahanshad N, Zalesky A, Kochunov P, Agartz I, Alloza C, Andreassen OA, Arango C, Banaj N, Bouix S, Bousman CA, Brouwer RM, Bruggemann J, Bustillo J, Cahn W, Calhoun V, Cannon D, Carr V, Catts S, Chen J, Chen JX, Chen X, Chiapponi C, Cho KK, Ciullo V, Corvin AS, Crespo-Facorro B, Cropley V, De Rossi P, Diaz-Caneja CM, Dickie EW, Ehrlich S, Fan FM, Faskowitz J, Fatouros-Bergman H, Flyckt L, Ford JM, Fouche JP, Fukunaga M, Gill M, Glahn DC, Gollub R, Goudzwaard ED, Guo H, Gur RE, Gur RC, Gurholt TP, Hashimoto R, Hatton SN, Henskens FA, Hibar DP, Hickie IB, Hong LE, Horacek J, Howells FM, Hulshoff Pol HE, Hyde CL, Isaev D, Jablensky A, Jansen PR, Janssen J, Jönsson EG, Jung LA, Kahn RS, Kikinis Z, Liu K, Klauser P, Knöchel C, Kubicki M, Lagopoulos J, Langen C, Lawrie S, Lenroot RK, Lim KO, Lopez-Jaramillo C, Lyall A, Magnotta V, Mandl RCW, Mathalon DH, McCarley RW, McCarthy-Jones S, McDonald C, McEwen S, McIntosh A, Melicher T, Mesholam-Gately RI, Michie PT, Mowry B, Mueller BA, Newell DT, O'Donnell P, Oertel-Knöchel V, Oestreich L, Paciga SA, Pantelis C, Pasternak O, Pearlson G, Pellicano GR, Pereira A, Pineda Zapata J, Piras F, Potkin SG, Preda A, Rasser PE, Roalf DR, Roiz R, Roos A, Rotenberg D, Satterthwaite TD, Savadjiev P, Schall U, Scott RJ, Seal ML, Seidman LJ, Shannon Weickert C, Whelan CD, Shenton ME, Kwon JS, Spalletta G, Spaniel F, Sprooten E, Stäblein M, Stein DJ, Sundram S, Tan Y, Tan S, Tang S, Temmingh HS, Westlye LT, Tønnesen S, Tordesillas-Gutierrez D, Doan NT, Vaidya J, van Haren NEM, Vargas CD, Vecchio D, Velakoulis D, Voineskos A, Voyvodic JQ, Wang Z, Wan P, Wei D, Weickert TW, Whalley H, White T, Whitford TJ, Wojcik JD, Xiang H, Xie Z, Yamamori H, Yang F, Yao N, Zhang G, Zhao J, van Erp TGM, Turner J, Thompson PM, Donohoe G. Widespread white matter microstructural differences in schizophrenia across 4322 individuals: results from the ENIGMA Schizophrenia DTI Working Group. Mol Psychiatry 2018; 23:1261-1269. [PMID: 29038599 PMCID: PMC5984078 DOI: 10.1038/mp.2017.170] [Citation(s) in RCA: 473] [Impact Index Per Article: 67.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Academic Contribution Register] [Received: 10/17/2016] [Revised: 05/02/2017] [Accepted: 06/07/2017] [Indexed: 12/15/2022]
Abstract
The regional distribution of white matter (WM) abnormalities in schizophrenia remains poorly understood, and reported disease effects on the brain vary widely between studies. In an effort to identify commonalities across studies, we perform what we believe is the first ever large-scale coordinated study of WM microstructural differences in schizophrenia. Our analysis consisted of 2359 healthy controls and 1963 schizophrenia patients from 29 independent international studies; we harmonized the processing and statistical analyses of diffusion tensor imaging (DTI) data across sites and meta-analyzed effects across studies. Significant reductions in fractional anisotropy (FA) in schizophrenia patients were widespread, and detected in 20 of 25 regions of interest within a WM skeleton representing all major WM fasciculi. Effect sizes varied by region, peaking at (d=0.42) for the entire WM skeleton, driven more by peripheral areas as opposed to the core WM where regions of interest were defined. The anterior corona radiata (d=0.40) and corpus callosum (d=0.39), specifically its body (d=0.39) and genu (d=0.37), showed greatest effects. Significant decreases, to lesser degrees, were observed in almost all regions analyzed. Larger effect sizes were observed for FA than diffusivity measures; significantly higher mean and radial diffusivity was observed for schizophrenia patients compared with controls. No significant effects of age at onset of schizophrenia or medication dosage were detected. As the largest coordinated analysis of WM differences in a psychiatric disorder to date, the present study provides a robust profile of widespread WM abnormalities in schizophrenia patients worldwide. Interactive three-dimensional visualization of the results is available at www.enigma-viewer.org.
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Abstract
Extensive nerve cell death occurs during the development of the central nervous system as well as in episodes of trauma and in neurodegenerative disease. The mechanistic details of how these cells die are poorly understood. Here we describe a unique oxidative stress-induced programmed cell death pathway called oxytosis, and outline pharmacological approaches which interfere with its execution. Oxidative glutamate toxicity, in which exogenous glutamate inhibits cystine uptake through the cystine/glutamate antiporter leading to a depletion of glutathione, is used as an example of oxytosis. It is shown that there is a sequential requirement for de novo macromolecular synthesis, lipoxygenase activation, reactive oxygen species production, and the opening of cGMP-gated channels which allow the influx of extracellular calcium. The translation initiation factor elF2alpha plays a central role in this pathway by regulating the levels of glutathione. Finally, examples are given in which the reduction in glutathione, the production of reactive oxygen species, and calcium influx can be experimentally manipulated to prevent cell death. Data are reviewed which suggest that oxytosis may be involved in nerve cell death associated with nervous system trauma and disease.
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Review |
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Brown CE, Howe L, Sousa K, Alley SC, Carrozza MJ, Tan S, Workman JL. Recruitment of HAT complexes by direct activator interactions with the ATM-related Tra1 subunit. Science 2001; 292:2333-7. [PMID: 11423663 DOI: 10.1126/science.1060214] [Citation(s) in RCA: 276] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 11/02/2022]
Abstract
Promoter-specific recruitment of histone acetyltransferase activity is often critical for transcriptional activation. We present a detailed study of the interaction between the histone acetyltransferase complexes SAGA and NuA4, and transcription activators. We demonstrate by affinity chromatography and photo-cross-linking label transfer that acidic activators directly interact with Tra1p, a shared subunit of SAGA and NuA4. Mutations within the COOH-terminus of Tra1p disrupted its interaction with activators and resulted in gene-specific transcriptional defects that correlated with lowered promoter-specific histone acetylation. These data demonstrate that the essential Tra1 protein serves as a common target for activators in both SAGA and NuA4 acetyltransferases.
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Tan S, Hall IP, Dewar J, Dow E, Lipworth B. Association between beta 2-adrenoceptor polymorphism and susceptibility to bronchodilator desensitisation in moderately severe stable asthmatics. Lancet 1997; 350:995-9. [PMID: 9329515 DOI: 10.1016/s0140-6736(97)03211-x] [Citation(s) in RCA: 276] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Academic Contribution Register] [Indexed: 02/05/2023]
Abstract
BACKGROUND In-vitro studies have suggested that polymorphisms of the beta 2-adrenoceptor may influence the desensitisation induced by beta 2-agonists. We investigated the influence of beta 2-AR polymorphism on the development of bronchodilator desensitisation in asthma patients. METHODS We carried out an analysis of 22 moderately severe stable asthmatics, mean age 38 years, FEV1 63% of predicted and FEF25-75 38% of predicted, who received a median inhaled corticosteroid dose of 1000 micrograms/day. Patients were randomly assigned inhaled placebo or inhaled formoterol 24 micrograms bid for 4 weeks each in a crossover study. Bronchodilator dose-response curves were made at the end of each treatment period by use of cumulative doses of formoterol (6-108 micrograms) with FEV1 and FEF25-75 measured 30 min after each dose, and up to 6 h after the last dose. We calculated the degree of bronchodilator desensitisation by comparing the dose-response (for maximum and 6 h) after placebo with that after formoterol, and expressed this degree as a percentage of placebo response. Patients were divided into groups according to genotype at codon 16: homozygous Arg 16 (n = 4), heterozygous Arg 16/Gly 16 (n = 8), and homozygous Gly 16 (n = 10). At codon 27: homozygous Gln 27 (n = 5), heterozygous Gln 27/Glu 27 (n = 11), and homozygous Glu 27 (n = 6). FINDINGS We found a significantly (p < 0.05) greater degree of bronchodilator desensitisation with homozygous Gly 16 than with homozygous Arg 16 for maximal FEV1 response: -8% (Arg 16) vs 46% (Gly 16); and for maximal FEF25-75 response: -32% (Arg 16) vs 74% (Gly 16; 95% CI 15-92% and 49-164%, respectively). Bronchodilator responses at 6 h were also significantly (p < 0.05) different for FEV1 and FEF25-75 when Arg 16 and Gly 16 were compared and values for heterozygous Arg 16/Gly 16 were intermediate. There was significantly greater desensitisation with Glu 27 than with Gln 27 for maximal FEF25-75 response: -7% (Gln 27) vs 68% (Glu 27), p = 0.05; and for 6 h FEF25-75 response: 43% (Gln 27) vs 93% (Glu 27), p < 0.05 (95% CI 2-147% and 5-94%, respectively). All patients who were homozygous Glu 27 were also homozygous Gly 16. INTERPRETATION We have found preliminary evidence that beta 2-adrenoceptor polymorphism is associated with altered beta 2-adrenoceptor expression in asthma patients. The homozygous Gly-16 form was significantly more prone to bronchodilator desensitisation than Arg 16, with the influence of Gly 16 dominating over any putative protective effects of Glu 27.
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7
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Abstract
The X-ray crystal structure of the transcription factor IIA (TFIIA) in complex with the TATA-box-binding protein (TBP) and TATA-element DNA is presented at 2.5 A resolution. TFIIA is composed of a beta-barrel and a four-helix bundle motif that together have a boot-like appearance. The beta-barrel extends the TBP beta-sheet and bridges over the DNA major groove immediately upstream of the TATA box. The four-helix bundle contributes substantially to the surface of the complex available for interaction with additional transcription factors.
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Tan S, Wood M, Maher P. Oxidative stress induces a form of programmed cell death with characteristics of both apoptosis and necrosis in neuronal cells. J Neurochem 1998; 71:95-105. [PMID: 9648855 DOI: 10.1046/j.1471-4159.1998.71010095.x] [Citation(s) in RCA: 261] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 11/20/2022]
Abstract
Oxidative stress is implicated in a number of neurological disorders including stroke, Parkinson's disease, and Alzheimer's disease. To study the effects of oxidative stress on neuronal cells, we have used an immortalized mouse hippocampal cell line (HT-22) that is particularly sensitive to glutamate. In these cells, glutamate competes for cystine uptake, leading to a reduction in glutathione and, ultimately, cell death. As it has been reported that protein kinase C activation inhibits glutamate toxicity in these cells and is also associated with the inhibition of apoptosis in other cell types, we asked if glutamate toxicity was via apoptosis. Morphologically, glutamate-treated cells underwent plasma membrane blebbing and cell shrinkage, but no DNA fragmentation was observed. At the ultrastructural level, there was damage to mitochondria and other organelles although the nuclei remained intact. Protein and RNA synthesis inhibitors as well as certain protease inhibitors protected the cells from glutamate toxicity. Both the macromolecular synthesis inhibitors and the protease inhibitors had to be added relatively soon after the addition of glutamate, suggesting that protein synthesis and protease activation are early and distinct steps in the cell death pathway. Thus, the oxidative stress brought about by treatment with glutamate initiates a series of events that lead to a form of cell death distinct from either necrosis or apoptosis.
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Abstract
The human serum response factor is a transcription factor belonging to the MADS domain protein family with members characterized from the plant and animal kingdoms. The X-ray crystal structure of the serum response factor core in a specific-recognition DNA complex shows that the functions of DNA binding, dimerization and accessory-factor interaction are compactly integrated into a novel protein unit. The intrinsic and induced conformation of the serum response element DNA is the principal DNA feature recognized in the specific complex.
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10
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Jodrell DI, Egorin MJ, Canetta RM, Langenberg P, Goldbloom EP, Burroughs JN, Goodlow JL, Tan S, Wiltshaw E. Relationships between carboplatin exposure and tumor response and toxicity in patients with ovarian cancer. J Clin Oncol 1992; 10:520-8. [PMID: 1548516 DOI: 10.1200/jco.1992.10.4.520] [Citation(s) in RCA: 240] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 12/27/2022] Open
Abstract
PURPOSE The study was undertaken to define the relationship between tumor response and carboplatin area under the curve (AUC) in patients with ovarian cancer; to study the relationship between carboplatin AUC and myelosuppression in the same population; to establish the true impact of carboplatin AUC, prior therapy, and pretreatment platelet and WBC counts on toxicity; and to define an optimal carboplatin exposure for treating patients with ovarian cancer. METHODS With the equation AUC = dose/(glomerular filtration rate [GFR]+25), carboplatin AUC (course 1) was calculated for 1,028 patients (450 previously untreated) who received single-agent carboplatin (40 to 1,000 mg/m2) for advanced ovarian cancer. GFR was measured (chromium-51-edathamil [51Cr-EDTA] or creatinine clearance) in all patients. RESULTS Regression analysis showed that carboplatin AUC, prior treatment, and Eastern Cooperative Oncology Group grade performance status (PS) are predictors of tumor response, thrombocytopenia, and leukopenia. Pretreatment platelet and WBC counts are additional predictors of thrombocytopenia and leukopenia, respectively. Although the likelihood of tumor response increased with increasing carboplatin AUC, this relationship was nonlinear. In all patient subsets, the likelihood of complete response (CR) or overall response did not increase significantly above a carboplatin AUC of 5 to 7 mg/mL x minutes. At any given carboplatin AUC, thrombocytopenia occurred more frequently than leukopenia, although both approached 100% as carboplatin AUC increased. Both thrombocytopenia and leukopenia were more frequent in pretreated than in untreated patients regardless of pretreatment count. At any carboplatin AUC, the influence of PS on likelihood of response and toxicity was profound. CONCLUSION Carboplatin dosing by AUC will lead to more predictable toxicity, and increasing carboplatin AUC above 5 to 7 mg/mL x minutes does not improve the likelihood of response but does increase myelotoxicity. Therefore, careful evaluation of high-dose carboplatin therapy in a prospective, randomized trial is needed before such treatment becomes accepted practice.
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11
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Abstract
Diamond & Carey (1986) have argued that expertise in face recognition depends on the ability to code configural properties in addition to isolated features. We tested this hypothesis in two experiments by comparing the effect of inversion on recognition of 'own race' (high expertise) and 'other race' (low expertise) faces. Use of configural information should be associated with a larger inversion effect than use of isolated features, and therefore inversion should produce a larger recognition decrement for own race than for other race faces. In Expt 1 there was a larger inversion effect in reaction times for recognition of own race faces than other race faces, for both European and Chinese subjects (ceiling effects made interpretation of accuracy difficult). In Expt 2 a larger own race inversion effect was found for recognition accuracy, when test face pairs were randomly selected, but not when they were matched on isolated features. Our results are largely consistent with the hypothesis that expertise is associated with greater use of configural information in faces.
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Campos GM, Peters JH, DeMeester TR, Oberg S, Crookes PF, Tan S, DeMeester SR, Hagen JA, Bremner CG. Multivariate analysis of factors predicting outcome after laparoscopic Nissen fundoplication. J Gastrointest Surg 1999; 3:292-300. [PMID: 10481122 DOI: 10.1016/s1091-255x(99)80071-7] [Citation(s) in RCA: 227] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Academic Contribution Register] [Indexed: 01/31/2023]
Abstract
Laparoscopic Nissen fundoplication has been applied with increasing frequency in the treatment of gastroesophageal reflux disease. The aim of this study was to determine the variables that predict outcome of laparoscopic Nissen fundoplication. A multivariate analysis was performed on data from 199 consecutive patients undergoing laparoscopic Nissen fundoplication. Variables included age, sex, body mass index, primary symptoms, clinical response to acid suppression therapy, erosive esophagitis, 24-hour esophageal pH score, and the percentage of time the esophageal pH was less than 4 on 24-hour pH monitoring, lower esophageal sphincter competence, status of the esophageal body motility, hiatal hernia, carditis, intestinal metaplasia of cardiac epithelium limited to the gastroesophageal junction, and Barrett's esophagus of any length. Clinical outcome was obtained from all patients at a median follow-up of 15 months (range 6 to 74 months) after surgery. One hundred seventy-three patients had an excellent or good outcome (87%) and 26 had a fair or poor outcome. Three factors were significantly predictive of a successful outcome: an abnormal 24-hour pH score (odds ratio = 5.4; 95% confidence interval [CI] = 1. 9-15.3), a typical primary symptom (odds ratio = 5.1; 95% CI = 1. 9-13.6), and a clinical response to acid suppression therapy (odds ratio = 3.3; 95% CI = 1.3-8.7). We conclude that 24-hour pH monitoring provides the strongest outcome predictor of laparoscopic Nissen fundoplication and that outcome is based more on the correct identification of the disease than on its severity.
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227 |
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Durnford DG, Deane JA, Tan S, McFadden GI, Gantt E, Green BR. A phylogenetic assessment of the eukaryotic light-harvesting antenna proteins, with implications for plastid evolution. J Mol Evol 1999; 48:59-68. [PMID: 9873077 DOI: 10.1007/pl00006445] [Citation(s) in RCA: 207] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 10/25/2022]
Abstract
The light-harvesting complexes (LHCs) are a superfamily of chlorophyll-binding proteins present in all photosynthetic eukaryotes. The Lhc genes are nuclear-encoded, yet the pigment-protein complexes are localized to the thylakoid membrane and provide a marker to follow the evolutionary paths of plastids with different pigmentation. The LHCs are divided into the chlorophyll a/b-binding proteins of the green algae, euglenoids, and higher plants and the chlorophyll a/c-binding proteins of various algal taxa. This work examines the phylogenetic position of the LHCs from three additional taxa: the rhodophytes, the cryptophytes, and the chlorarachniophytes. Phylogenetic analysis of the LHC sequences provides strong statistical support for the clustering of the rhodophyte and cryptomonad LHC sequences within the chlorophyll a/c-binding protein lineage, which includes the fucoxanthin-chlorophyll proteins (FCP) of the heterokonts and the intrinsic peridinin-chlorophyll proteins (iPCP) of the dinoflagellates. These associations suggest that plastids from the heterokonts, haptophytes, cryptomonads, and the dinoflagellate, Amphidinium, evolved from a red algal-like ancestor. The Chlorarachnion LHC is part of the chlorophyll a/b-binding protein assemblage, consistent with pigmentation, providing further evidence that its plastid evolved from a green algal secondary endosymbiosis. The Chlorarachnion LHC sequences cluster with the green algal LHCs that are predominantly associated with photosystem II (LHCII). This suggests that the green algal endosymbiont that evolved into the Chlorarachnion plastid was acquired following the emergence of distinct LHCI and LHCII complexes.
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14
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Abstract
The structure of a complex containing the homeodomain repressor protein MATalpha2 and the MADS-box transcription factor MCM1 bound to DNA has been determined by X-ray crystallography at 2.25 A resolution. It reveals the protein-protein interactions responsible for cooperative binding of MATalpha2 and MCM1 to DNA. The otherwise flexible amino-terminal extension of the MATalpha2 homeodomain forms a beta-hairpin that grips the MCM1 surface through parallel beta-strand hydrogen bonds and close-packed, predominantly hydrophobic, side chains. DNA bending induced by MCM1 brings the two proteins closer together, facilitating their interaction. An unusual feature of the complex is that an eight-amino-acid sequence adopts an alpha-helical conformation in one of two copies of the MATalpha2 monomer and a beta-strand conformation in the other. This 'chameleon' sequence of MATalpha2 may be important for recognizing natural operator sites.
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203 |
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Abstract
The AXR1 (auxin-resistant) protein, which has features of the ubiquitin-activating enzyme E1, is required for normal response to the plant hormone auxin in Arabidopsis thaliana. ECR1 functions together with AXR1 to activate members of the RUB/NEDD8 family of ubiquitin-related proteins. Extracts from mutant seedlings lacking AXR1 did not promote formation of the RUB-ECR1 thiolester, indicating that AXR1 is the major activity in this tissue. AXR1 was localized primarily to the nucleus of dividing and elongating cells, suggesting that the targets of RUB modification are nuclear. These results indicate that auxin response depends on RUB modification of one or more nuclear proteins.
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Al-Khalidi FQ, Saatchi R, Burke D, Elphick H, Tan S. Respiration rate monitoring methods: a review. Pediatr Pulmonol 2011; 46:523-9. [PMID: 21560260 DOI: 10.1002/ppul.21416] [Citation(s) in RCA: 184] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Academic Contribution Register] [Received: 07/11/2010] [Revised: 11/19/2010] [Accepted: 11/19/2010] [Indexed: 11/09/2022]
Abstract
Respiration rate is an important indicator of a person's health, and thus it is monitored when performing clinical evaluations. There are different approaches for respiration monitoring, but generally they can be classed as contact or noncontact. For contact methods, the sensing device (or part of the instrument containing it) is attached to the subject's body. For noncontact approaches the monitoring is performed by an instrument that does not make any contact with the subject. In this article a review of respiration monitoring approaches (both contact and noncontact) is provided. Concerns related to the patient's recording comfort, recording hygiene, and the accuracy of respiration rate monitoring have resulted in the development of a number of noncontact respiration monitoring approaches. A description of thermal imaging based and vision based noncontact respiration monitoring approaches we are currently developing is provided.
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Review |
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184 |
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Tan S. A modular polycistronic expression system for overexpressing protein complexes in Escherichia coli. Protein Expr Purif 2001; 21:224-34. [PMID: 11162410 DOI: 10.1006/prep.2000.1363] [Citation(s) in RCA: 182] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 11/22/2022]
Abstract
To facilitate studies of multicomponent protein complexes, I have developed an Escherichia coli expression system which coexpresses up to four polypeptides from a single plasmid. The modular nature of the system enables efficient subcloning of a gene into each of the 4 cassettes in the polycistronic expression vector. Restriction sites present in the polycistronic expression vector allow both affinity tagged and untagged complexes to be overexpressed. I demonstrate successful use of the expression system for binary and ternary complexes, including the reconstitution of the VHL-elonginC-elonginB complex in E. coli and purification of the complex by affinity and ion-exchange chromatography. This polycistronic expression system should provide an important alternative to in vitro reconstitution of multicomponent complexes.
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Kamel S, Horton L, Ysebaert L, Levade M, Burbury K, Tan S, Cole-Sinclair M, Reynolds J, Filshie R, Schischka S, Khot A, Sandhu S, Keating MJ, Nandurkar H, Tam CS. Ibrutinib inhibits collagen-mediated but not ADP-mediated platelet aggregation. Leukemia 2015; 29:783-7. [PMID: 25138588 DOI: 10.1038/leu.2014.247] [Citation(s) in RCA: 174] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 06/23/2014] [Revised: 08/07/2014] [Accepted: 08/14/2014] [Indexed: 02/03/2023]
Abstract
The BTK (Bruton's tyrosine kinase) inhibitor ibrutinib is associated with an increased risk of bleeding. A previous study reported defects in collagen- and adenosine diphosphate (ADP)-dependent platelet responses when ibrutinib was added ex vivo to patient samples. Whereas the collagen defect is expected given the central role of BTK in glycoprotein VI signaling, the ADP defect lacks a mechanistic explanation. In order to determine the real-life consequences of BTK platelet blockade, we performed light transmission aggregometry in 23 patients receiving ibrutinib treatment. All patients had reductions in collagen-mediated platelet aggregation, with a significant association between the degree of inhibition and the occurrence of clinical bleeding or bruising (P=0.044). This collagen defect was reversible on drug cessation. In contrast to the previous ex vivo report, we found no in vivo ADP defects in subjects receiving standard doses of ibrutinib. These results establish platelet light transmission aggregometry as a method for gauging, at least qualitatively, the severity of platelet impairment in patients receiving ibrutinib treatment.
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174 |
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Hahn S, Haselhorst U, Tan S, Quadbeck B, Schmidt M, Roesler S, Kimmig R, Mann K, Janssen OE. Low Serum 25-Hydroxyvitamin D Concentrations are Associated with Insulin Resistance and Obesity in Women with Polycystic Ovary Syndrome. Exp Clin Endocrinol Diabetes 2006; 114:577-83. [PMID: 17177140 DOI: 10.1055/s-2006-948308] [Citation(s) in RCA: 159] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Academic Contribution Register] [Indexed: 10/23/2022]
Abstract
Insulin resistance (IR) and central obesity are common features of the polycystic ovary syndrome (PCOS). Vitamin D is thought to play a role in the pathogenesis of type 2 diabetes by affecting insulin metabolism. The aim of our study was to investigate the effect of 25-hydroxyvitamin D (25-OH-VD) on metabolic parameters and IR in PCOS. In 120 untreated PCOS patients (median age 28 years) levels of 25-OH-VD (radioimmunoassay method provided by DiaSorin), calcium and anorganic phosphate were measured. In addition, endocrine and metabolic variables were evaluated and a glucose tolerance test was performed to assess indices of IR. In the entire PCOS cohort, 25-OH-VD concentrations were negatively correlated with body mass index (r=-0.2765), body fat (r=-0.2490), HOMA-IR (r=-0.1947), hyperinsulinemia (r=-0.1892) and leptin levels (r=-0.2834), and positively correlated with HDL cholesterol (r=0.2630) (all p<0.05). Subgroup analysis of lean, overweight and obese women revealed significant higher 25-OH-VD levels in lean women. Differences remained significant when women were divided according to their 25-OH-VD levels. Women with hypovitaminosis D (<9 ng/ml) had higher mean BMI, indices of IR and leptin levels compared to women with normal serum levels (all p<0.05). Analysis of vitamin D and biochemical endocrine PCOS features revealed a significant correlation only between 25-OH-VD and sex hormone-binding globulin as well as the free androgen index. In conclusion, in PCOS women, low 25-OH-VD levels are associated with obesity and insulin resistance but not with PCOS per se.
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Tan S. The degree of deacetylation of chitosan: advocating the first derivative UV-spectrophotometry method of determination. Talanta 1998; 45:713-9. [DOI: 10.1016/s0039-9140(97)00288-9] [Citation(s) in RCA: 144] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 02/05/1997] [Revised: 07/24/1997] [Accepted: 07/28/1997] [Indexed: 10/18/2022]
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Flaus A, Luger K, Tan S, Richmond TJ. Mapping nucleosome position at single base-pair resolution by using site-directed hydroxyl radicals. Proc Natl Acad Sci U S A 1996; 93:1370-5. [PMID: 8643638 PMCID: PMC39944 DOI: 10.1073/pnas.93.4.1370] [Citation(s) in RCA: 139] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 02/01/2023] Open
Abstract
A base-pair resolution method for determining nucleosome position in vitro has been developed to com- plement existing, less accurate methods. Cysteaminyl EDTA was tethered to a recombinant histone octamer via a mutant histone H4 with serine 47 replaced by cysteine. When assembled into nucleosome core particles, the DNA could be cut site specifically by hydroxyl radical-catalyzed chain scission by using the Fenton reaction. Strand cleavage occurs mainly at a single nucleotide close to the dyad axis of the core particle, and assignment of this location via the symmetry of the nucleosome allows base-pair resolution mapping of the histone octamer position on the DNA. The positions of the histone octamer and H3H4 tetramer were mapped on a 146-bp Lytechinus variegatus 5S rRNA sequence and a twofold-symmetric derivative. The weakness of translational determinants of nucleosome positioning relative to the overall affinity of the histone proteins for this DNA is clearly demonstrated. The predominant location of both histone octamer and H3H4 tetramer assembled on the 5S rDNA is off center. Shifting the nucleosome core particle position along DNA within a conserved rotational phase could be induced under physiologically relevant conditions. Since nucleosome shifting has important consequences for chromatin structure and gene regulation, an approach to the thermodynamic characterization of this movement is proposed. This mapping method is potentially adaptable for determining nucleosome position in chromatin in vivo.
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Eeles RA, Tan S, Wiltshaw E, Fryatt I, A'Hern RP, Shepherd JH, Harmer CL, Blake PR, Chilvers CE. Hormone replacement therapy and survival after surgery for ovarian cancer. BMJ (CLINICAL RESEARCH ED.) 1991; 302:259-62. [PMID: 1998789 PMCID: PMC1668928 DOI: 10.1136/bmj.302.6771.259] [Citation(s) in RCA: 119] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Academic Contribution Register] [Indexed: 12/29/2022]
Abstract
OBJECTIVE To evaluate whether hormone replacement therapy affects survival in women who have undergone bilateral salphingo-oophorectomy because of epithelial ovarian cancer. DESIGN Retrospective analysis by review of patients' notes and questionnaires completed by general practitioners to compare the overall survival and disease free survival in patients with ovarian cancer who did or did not receive hormone replacement therapy after diagnosis. Data were analysed by Cox regression, with hormone replacement therapy as a time dependent covariate because patients who received hormone replacement did so at different times after diagnosis. SETTING Gynaecological oncology unit of Royal Marsden Hospital. PATIENTS 373 patients aged 50 years or younger who attended the hospital from 1972 to 1988. All of the women had undergone bilateral salpingoophorectomy for epithelial ovarian cancer. In all, 78 had received hormone replacement therapy, starting at a median of four months after diagnosis. INTERVENTION A questionnaire was sent to the general practitioners of all patients who were not recorded as having received hormone replacement therapy. MAIN OUTCOME MEASURES Overall survival and disease free survival. RESULTS There was no significant difference in survival between women receiving hormone replacement therapy and those not receiving it after accounting for the effects of other known prognostic factors (stage of cancer, differentiation of tumour, histological results, and time to relapse). The relative risk of dying in those who received hormone replacement therapy was 0.73 (95% confidence interval 0.44 to 1.20). In addition, there was no significant difference in disease free survival (relative risk in those receiving hormone replacement therapy was 0.90; 95% confidence interval 0.52 to 1.54). CONCLUSIONS This study shows that hormone replacement therapy is unlikely to have a detrimental effect on the prognosis of patients with ovarian cancer, but this would be shown conclusively only by a randomised controlled trial.
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Abstract
Our studies using proteases to probe protein structure establish that binding to the upstream activating sequences (UASs) of two different yeast a-specific genes induces a conformational change in the pheromone/receptor transcription factor (PRTF), which is not observed upon binding to the UASs of either of two alpha-specific genes. We propose that this selective structural alteration exposes an activation region of PRTF when it binds a-specific genes, switching these genes on. The transcriptional activator MAT alpha 1 may activate alpha-specific genes by binding to the PRTF-alpha-specific UAS complex and unmasking the otherwise hidden activation surface of PRTF. We also show that the N-terminal third of PRTF is sufficient for specific DNA binding, while the middle third of the protein interacts with MAT alpha 1.
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Tan S, Yokoyama Y, Dickens E, Cash TG, Freeman BA, Parks DA. Xanthine oxidase activity in the circulation of rats following hemorrhagic shock. Free Radic Biol Med 1993; 15:407-14. [PMID: 8225022 DOI: 10.1016/0891-5849(93)90040-2] [Citation(s) in RCA: 103] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Academic Contribution Register] [Indexed: 01/29/2023]
Abstract
Reactive oxygen metabolites generated from xanthine oxidase play an important role in the pathogenesis of ischemia-induced tissue injury. In a hemorrhagic shock model of ischemia-reperfusion, the intracellular enzyme xanthine oxidase was released into the vasculature. This intravascular source of superoxide (O2.-) and hydrogen peroxide (H2O2) interacted reversibly with glycosaminoglycans of vascular endothelium and markedly concentrated xanthine oxidase at cell surfaces, enhancing its ability to produce extensive damage to remote tissues. Rats were made hypotensive by hemorrhage, maintained for 2h, and reinfused with shed blood. Blood samples were obtained prior to hemorrhage and 15, 30, 60, and 90 min after reperfusion for determination of xanthine oxidase (XO), lactate dehydrogenase (LDH), and alanine transaminase (AST). These enzymes were not significantly elevated in control animals. Reperfusion after hemorrhage-induced ischemia resulted in significantly elevated AST and LDH in both low heparin (100 U/h) and high heparin (1000 U/h) groups. Xanthine oxidase was detected in the circulation only after 90 min reperfusion in the low heparin group and was elevated during the entire reperfusion period in the high heparin group. Studies with cultured vascular endothelium showed significant heparin-reversible binding of XO to cellular glycosaminoglycans. These results suggest that XO can gain access to the circulation following ischemia, where it then binds to the vascular endothelial cells to produce site-specific oxidant injury to organs remote from the site of XO release.
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Tan S, Evans R, Singh B. Herbicidal inhibitors of amino acid biosynthesis and herbicide-tolerant crops. Amino Acids 2006; 30:195-204. [PMID: 16547651 DOI: 10.1007/s00726-005-0254-1] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 05/18/2005] [Accepted: 07/05/2005] [Indexed: 11/26/2022]
Abstract
Acetohydroxyacid synthase (AHAS) inhibitors interfere with branched-chain amino acid biosynthesis by inhibiting AHAS. Glyphosate affects aromatic amino acid biosynthesis by inhibiting 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). Glufosinate inhibits glutamine synthetase and blocks biosynthesis of glutamine. AHAS gene variants that confer tolerance to AHAS inhibitors have been discovered in plants through selection or mutagenesis. Imidazolinone-tolerant crops have been commercialized based on these AHAS gene variants. A modified maize EPSPS gene and CP4-EPSPS gene from Agrobacterium sp. have been used to transform plants for target-based tolerance to glyphosate. A gox gene isolated from Ochrobactrum anthropi has also been employed to encode glyphosate oxidoreductase to detoxify glyphosate in plants. Glyphosate-tolerant crops with EPSPS transgene alone or both EPSPS and gox transgenes have been commercialized. Similarly, bar and pat genes isolated from Streptomyces hygroscopicus and S. viridochromogenes, respectively, have been inserted into plants to encode phosphinothricin N-acetyltransferase to detoxify glufosinate. Glufosinate-tolerant crops have been commercialized using one of these two transgenes.
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