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Abstract
In response to DNA damage and replication blocks, cells prevent cell cycle progression through the control of critical cell cycle regulators. We identified Chk2, the mammalian homolog of the Saccharomyces cerevisiae Rad53 and Schizosaccharomyces pombe Cds1 protein kinases required for the DNA damage and replication checkpoints. Chk2 was rapidly phosphorylated and activated in response to replication blocks and DNA damage; the response to DNA damage occurred in an ataxia telangiectasia mutated (ATM)-dependent manner. In vitro, Chk2 phosphorylated Cdc25C on serine-216, a site known to be involved in negative regulation of Cdc25C. This is the same site phosphorylated by the protein kinase Chk1, which suggests that, in response to DNA damage and DNA replicational stress, Chk1 and Chk2 may phosphorylate Cdc25C to prevent entry into mitosis.
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955 |
2
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Garcia KC, Degano M, Pease LR, Huang M, Peterson PA, Teyton L, Wilson IA. Structural basis of plasticity in T cell receptor recognition of a self peptide-MHC antigen. Science 1998; 279:1166-72. [PMID: 9469799 DOI: 10.1126/science.279.5354.1166] [Citation(s) in RCA: 550] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The T cell receptor (TCR) inherently has dual specificity. T cells must recognize self-antigens in the thymus during maturation and then discriminate between foreign pathogens in the periphery. A molecular basis for this cross-reactivity is elucidated by the crystal structure of the alloreactive 2C TCR bound to self peptide-major histocompatibility complex (pMHC) antigen H-2Kb-dEV8 refined against anisotropic 3.0 angstrom resolution x-ray data. The interface between peptide and TCR exhibits extremely poor shape complementarity, and the TCR beta chain complementarity-determining region 3 (CDR3) has minimal interaction with the dEV8 peptide. Large conformational changes in three of the TCR CDR loops are induced upon binding, providing a mechanism of structural plasticity to accommodate a variety of different peptide antigens. Extensive TCR interaction with the pMHC alpha helices suggests a generalized orientation that is mediated by the Valpha domain of the TCR and rationalizes how TCRs can effectively "scan" different peptides bound within a large, low-affinity MHC structural framework for those that provide the slight additional kinetic stabilization required for signaling.
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MESH Headings
- Animals
- Crystallization
- Crystallography, X-Ray
- H-2 Antigens/chemistry
- H-2 Antigens/immunology
- H-2 Antigens/metabolism
- Ligands
- Mice
- Mice, Transgenic
- Models, Molecular
- Mutation
- Oligopeptides/chemistry
- Oligopeptides/immunology
- Oligopeptides/metabolism
- Protein Conformation
- Protein Structure, Secondary
- Receptors, Antigen, T-Cell, alpha-beta/chemistry
- Receptors, Antigen, T-Cell, alpha-beta/immunology
- Receptors, Antigen, T-Cell, alpha-beta/metabolism
- Recombinant Proteins
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27 |
550 |
3
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Huang M, Zhou Z, Elledge SJ. The DNA replication and damage checkpoint pathways induce transcription by inhibition of the Crt1 repressor. Cell 1998; 94:595-605. [PMID: 9741624 DOI: 10.1016/s0092-8674(00)81601-3] [Citation(s) in RCA: 406] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have identified the yeast CRT1 gene as an effector of the DNA damage and replication checkpoint pathway. CRT1 encodes a DNA-binding protein that recruits the general repressors Ssn6 and Tup1 to the promoters of damage-inducible genes. Derepression of the Crt1 regulon suppresses the lethality of mec1 and rad53 null alleles and is essential for cell viability during replicative stress. In response to DNA damage and replication blocks, Crt1 becomes hyperphosphorylated and no longer binds DNA, resulting in transcriptional induction. CRT1 is autoregulated and is itself induced by DNA damage, indicating the existence of a negative feedback pathway that facilitates return to the repressed state after elimination of damage. The inhibition of an autoregulatory repressor in response to DNA damage is a strategy conserved throughout prokaryotic and eukaryotic evolution.
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406 |
4
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Huang M, Orenstein JM, Martin MA, Freed EO. p6Gag is required for particle production from full-length human immunodeficiency virus type 1 molecular clones expressing protease. J Virol 1995; 69:6810-8. [PMID: 7474093 PMCID: PMC189593 DOI: 10.1128/jvi.69.11.6810-6818.1995] [Citation(s) in RCA: 396] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The human immunodeficiency virus type 1 (HIV-1) Gag protein precursor, Pr55Gag, contains at its C-terminal end a proline-rich, 6-kDa domain designated p6. Two functions have been proposed for p6: incorporation of the HIV-1 accessory protein Vpr into virus particles and virus particle production. To characterize the role of p6 in the HIV-1 life cycle and to map functional domains within p6, we introduced a number of nonsense and single and multiple amino acid substitution mutations into p6. Following the introduction of the mutations into the full-length HIV-1 molecular clone pNL4-3, the effects on Gag protein expression and processing, virus particle production, and virus infectivity were analyzed. The production of mutant virus particles was also examined by transmission electron microscopy. The results indicate that (i) p6 is required for efficient virus particle production from a full-length HIV-1 molecular clone; (ii) a Pro-Thr-Ala-Pro sequence, located between residues 7 and 10 of p6, is critical for virus particle production; (iii) mutations outside the Pro-Thr-Ala-Pro motif have little or no effect on virus assembly and release; (iv) the p6 defect is manifested at a late stage in the budding process; and (v) mutations in p6 that severely reduce virion production in HeLa cells also block or significantly delay the establishment of a productive infection in the CEM (12D-7) T-cell line. We further demonstrate that mutational inactivation of the viral protease reverses the p6 defect, suggesting a functional linkage between p6 and the proteolytic processing of the Gag precursor protein during the budding of progeny virions.
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Gasch AP, Huang M, Metzner S, Botstein D, Elledge SJ, Brown PO. Genomic expression responses to DNA-damaging agents and the regulatory role of the yeast ATR homolog Mec1p. Mol Biol Cell 2001; 12:2987-3003. [PMID: 11598186 PMCID: PMC60150 DOI: 10.1091/mbc.12.10.2987] [Citation(s) in RCA: 388] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2001] [Revised: 06/04/2001] [Accepted: 07/27/2001] [Indexed: 11/11/2022] Open
Abstract
Eukaryotic cells respond to DNA damage by arresting the cell cycle and modulating gene expression to ensure efficient DNA repair. The human ATR kinase and its homolog in yeast, MEC1, play central roles in transducing the damage signal. To characterize the role of the Mec1 pathway in modulating the cellular response to DNA damage, we used DNA microarrays to observe genomic expression in Saccharomyces cerevisiae responding to two different DNA-damaging agents. We compared the genome-wide expression patterns of wild-type cells and mutants defective in Mec1 signaling, including mec1, dun1, and crt1 mutants, under normal growth conditions and in response to the methylating-agent methylmethane sulfonate (MMS) and ionizing radiation. Here, we present a comparative analysis of wild-type and mutant cells responding to these DNA-damaging agents, and identify specific features of the gene expression responses that are dependent on the Mec1 pathway. Among the hundreds of genes whose expression was affected by Mec1p, one set of genes appears to represent an MEC1-dependent expression signature of DNA damage. Other aspects of the genomic responses were independent of Mec1p, and likely independent of DNA damage, suggesting the pleiotropic effects of MMS and ionizing radiation. The complete data set as well as supplemental materials is available at http://www-genome.stanford.edu/mec1.
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Comparative Study |
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Huang M, Chalfie M. Gene interactions affecting mechanosensory transduction in Caenorhabditis elegans. Nature 1994; 367:467-70. [PMID: 7509039 DOI: 10.1038/367467a0] [Citation(s) in RCA: 310] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Genetic screening has identified a group of mec (mechanosensory) genes that are required for the function of a set of six touch-receptor neurons in the nematode Caenorhabditis elegans. Such genes potentially encode components of the mechanosensory apparatus. We have cloned one of these genes, mec-10, which is a member of the degenerin gene family (genes such as mec-4 and deg-1 that can be mutated to cause neurodegeneration). Because components of an amiloride-sensitive sodium channel (alpha, beta and gamma rENaC) from rat share considerable sequence similarity with the C. elegans genes, it is likely that degenerins may function as channel proteins. Here we show that two degenerin homologues (mec-4 and mec-10) are expressed in the same cells, although each provides a unique function. Based on genetic data of mutations affecting mec-10-induced degeneration, we propose that the products of three genes (mec-4, mec-10 and mec-6) form a complex needed for mechanosensation, and that several other mec genes may be important in regulating the putative channel complex.
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31 |
310 |
7
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Abstract
One of the most important clinical applications of hydroxyapatite (HA) is as a coating on metal implants, especially plasma-sprayed HA coating applied on Ti alloy substrate. However, the poor bonding strength between HA and Ti alloy has been of concern to orthopedists. In this paper, an attempt has been made to enhance the bonding strength of HA coating by forming a composite coating with Ti. The bioactivity of the coating has also been studied. HA/Ti composite coatings were prepared via atmospheric plasma spraying on Ti-6Al-4V alloy substrates. The bond strength evaluation of HA/Ti composite coatings was performed according to ASTM C-633 test method. X-ray diffractometer and scanning electron microscopy were applied to identify the phases and the morphologies of the coatings. The bioactivity of HA/Ti composite coating was qualified by immersion of coating in simulated body fluid (SBF). The obtained results revealed that the addition of Ti to HA improved the bonding strength of coating significantly. In the SBF test, the coating surface was covered by carbonate-apatite, which was testified by X-ray photoelectron spectroscope, indicating good bioactivity for HA/Ti composite coating. The bioactivity of the coating has not been reduced by the addition of Ti.
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25 |
293 |
8
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Cho RJ, Huang M, Campbell MJ, Dong H, Steinmetz L, Sapinoso L, Hampton G, Elledge SJ, Davis RW, Lockhart DJ. Transcriptional regulation and function during the human cell cycle. Nat Genet 2001; 27:48-54. [PMID: 11137997 DOI: 10.1038/83751] [Citation(s) in RCA: 290] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
We report here the transcriptional profiling of the cell cycle on a genome-wide scale in human fibroblasts. We identified approximately 700 genes that display transcriptional fluctuation with a periodicity consistent with that of the cell cycle. Systematic analysis of these genes revealed functional organization within groups of coregulated transcripts. A diverse set of cytoskeletal reorganization genes exhibit cell-cycle-dependent regulation, indicating that biological pathways are redirected for the execution of cell division. Many genes involved in cell motility and remodeling of the extracellular matrix are expressed predominantly in M phase, indicating a mechanism for balancing proliferative and invasive cellular behavior. Transcripts upregulated during S phase displayed extensive overlap with genes induced by DNA damage; cell-cycle-regulated transcripts may therefore constitute coherent programs used in response to external stimuli. Our data also provide clues to biological function for hundreds of previously uncharacterized human genes.
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24 |
290 |
9
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Maynard AT, Huang M, Rice WG, Covell DG. Reactivity of the HIV-1 nucleocapsid protein p7 zinc finger domains from the perspective of density-functional theory. Proc Natl Acad Sci U S A 1998; 95:11578-83. [PMID: 9751708 PMCID: PMC21683 DOI: 10.1073/pnas.95.20.11578] [Citation(s) in RCA: 256] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The reaction of the human immunodeficiency virus type 1 (HIV-1) nucleocapsid protein p7 (NCp7) with a variety of electrophilic agents was investigated by experimental measurements of Trp37 fluorescence decay and compared with theoretical measures of reactivity based on density-functional theory in the context of the hard and soft acids and bases principle. Statistically significant correlations were found between rates of reaction and the ability of these agents to function as soft electrophiles. Notably, the molecular property that correlated strongest was the ratio of electronegativity to hardness, chi2/eta, a quantity related to the capacity of an electrophile to promote a soft (covalent) reaction. Electronic and steric determinants of the reaction were also probed by Fukui function and frontier-orbital overlap analysis in combination with protein-ligand docking methods. This analysis identified selective ligand docking regions within the conserved zinc finger domains that promoted reaction. The Cys49 thiolate was found overall to be the NCp7 site most susceptible to electrophilic attack.
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research-article |
27 |
256 |
10
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Chapple CR, Rechberger T, Al-Shukri S, Meffan P, Everaert K, Huang M, Ridder A. Randomized, double-blind placebo- and tolterodine-controlled trial of the once-daily antimuscarinic agent solifenacin in patients with symptomatic overactive bladder. BJU Int 2004; 93:303-10. [PMID: 14764127 DOI: 10.1111/j.1464-410x.2004.04606.x] [Citation(s) in RCA: 245] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVE To assess in a phase 3a trial the efficacy of solifenacin succinate, a once-daily oral antimuscarinic agent in development at 5-mg and 10-mg dosage strengths, for the treatment of overactive bladder (OAB) (Yamanouchi Pharmaceutical Co. Ltd, Tokyo, Japan) compared with placebo in patients with symptoms of OAB, i.e. urgency, incontinence, and frequency, with additional objectives being to assess the safety and tolerability of solifenacin and to compare the efficacy and safety of solifenacin with tolterodine 2 mg twice daily. PATIENTS AND METHODS The study was an international, multicentre, randomized, double-blind, tolterodine- and placebo-controlled trial conducted at 98 centres. Adult patients with symptomatic OAB for > or = 3 months were eligible; after a single-blind 2-week placebo run-in period patients were randomized equally to a 12-week double-blind treatment with either tolterodine 2 mg twice daily, placebo, solifenacin 5 mg or 10 mg once daily. Efficacy variables included change from baseline in the mean number of urgency, incontinence and urge incontinence episodes, and change from baseline in voids/24 h and mean volume voided/void. RESULTS In all, 1281 patients were enrolled, 1081 randomized and 1077 treated; 1033 were evaluated for efficacy. Compared with placebo, the change from baseline (-1.41, -32.7%) in the mean number of urgency episodes per 24 h was statistically significantly lower with solifenacin 5 mg (-2.85, -51.9%) and 10 mg (-3.07, -54.7%; both P < 0.001), but not with tolterodine (-2.05, -37.9%; P = 0.0511). There was a statistically insignificant decrease in episodes of incontinence with tolterodine (-1.14; P = 0.1122) but a significant decrease in patients treated with solifenacin 5 (-1.42; P = 0.008) and 10 mg (-1.45; P = 0.0038). Compared with placebo (-1.20, -8.1%) the mean number of voids/24 h was significantly lower in patients receiving tolterodine (-1.88, -15%; P = 0.0145), solifenacin 5 (-2.19, -17%) and 10 mg (-2.61, -20%; both P < 0.001). The mean volume voided/void was also significantly higher with all three active treatments (P < 0.001). Solifenacin was well tolerated; compared with placebo (4.9%), dry mouth (the most common side-effect), mostly mild, was reported in 18.6% of patients receiving tolterodine, 14.0% receiving 5 mg and 21.3% receiving 10 mg solifenacin. CONCLUSION Solifenacin 5 and 10 mg once daily improved urgency and other symptoms of OAB, and was associated with an acceptable level of anticholinergic side-effects. Solifenacin demonstrated significantly favourable efficacy to side-effect ratio in treating symptomatic OAB.
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245 |
11
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Cardozo L, Lisec M, Millard R, van Vierssen Trip O, Kuzmin I, Drogendijk TE, Huang M, Ridder AM. Randomized, double-blind placebo controlled trial of the once daily antimuscarinic agent solifenacin succinate in patients with overactive bladder. J Urol 2005; 172:1919-24. [PMID: 15540755 DOI: 10.1097/01.ju.0000140729.07840.16] [Citation(s) in RCA: 222] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE In this phase 3 trial we assessed the efficacy of solifenacin 5 mg and 10 mg daily in patients with symptoms related to overactive bladder. In addition, we assessed the safety and acceptability of solifenacin. MATERIALS AND METHODS The study was a multicenter, multinational, randomized, double-blind, placebo controlled trial. Patients were randomized to 12-week once daily treatment with solifenacin 5 mg, solifenacin 10 mg or placebo. The primary efficacy variable was changed from baseline to study end point in mean number of micturitions per 24 hours. Secondary efficacy variables included changes from baseline in mean number of urgency, nocturia and incontinence episodes per 24 hours, and mean volume voided per micturition. RESULTS Compared with changes obtained with placebo (-1.59), micturitions per 24 hours were statistically significantly decreased with solifenacin 5 mg (-2.37, p = 0.0018) and solifenacin 10 mg (-2.81, p = 0.0001). A statistically significant decrease was observed in the number of incontinence episodes with both solifenacin doses (5 mg, p = 0.002 and 10 mg, p = 0.016). This effect was also seen for episodes of urge incontinence (5 mg, p = 0.014 and 10 mg, p = 0.042). Of patients reporting incontinence at baseline, fully 50% achieved continence after treatment with solifenacin. Episodes of nocturia were statistically significantly decreased in patients treated with solifenacin 10 mg (-0.71, -38.5%) versus placebo (-0.52, -16.4%, p = 0.036). Episodes of urgency were statistically significantly reduced with solifenacin 5 mg (-2.84, -51%, p = 0.003) and solifenacin 10 mg (-2.90, -52%, p = 0.002). Mean volume voided per micturition was statistically significantly increased with both solifenacin doses (p = 0.0001). Treatment with solifenacin was well tolerated. Dry mouth, mostly mild in severity, was reported in 7.7% of patients receiving solifenacin 5 mg and 23% receiving solifenacin 10 mg (vs 2.3% with placebo). CONCLUSIONS In this study treatment with solifenacin 5 mg and 10 mg once daily significantly improved all the major symptoms of overactive bladder including frequency, urgency and incontinence. Solifenacin 10 mg also decreased the frequency of nocturia. Solifenacin therapy was associated with a favorable tolerability profile and a low incidence of dry mouth, especially at the 5 mg starting dose.
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Randomized Controlled Trial |
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222 |
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Huang M, Gu G, Ferguson EL, Chalfie M. A stomatin-like protein necessary for mechanosensation in C. elegans. Nature 1995; 378:292-5. [PMID: 7477350 DOI: 10.1038/378292a0] [Citation(s) in RCA: 220] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The mec-2 gene is required for the function of a set of six touch receptor neurons in the nematode Caenorhabditis elegans; mec-2 mutants, which are touch-insensitive, have touch cells that appear morphologically normal. Gene interaction studies suggest that mec-2 positively regulates the activity of the putative mechanosensory transduction channel (and the present paper), comprised in part of proteins encoded by the two degenerin genes mec-4 and mec-10 The central region of the mec-2 protein (MEC-2) is very similar to stomatin, an integral membrane protein (band 7.2b) in human red blood cells that is thought to regulate cation conductance. MEC-2-LacZ fusions are distributed along the touch receptor axons. This axonal distribution, which is mediated by the mec-2-specific amino terminus, is disrupted by mutations in mec-12, an alpha-tubulin gene needed for touch cell function. Our results indicate that MEC-2 links the mechanosensory channel and the microtubule cytoskeleton of the touch receptor neurons. Such linkage provides the basis for a mechanism of mechanosensation whereby microtubule displacement leads to channel opening.
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Burke WM, Jin X, Lin HJ, Huang M, Liu R, Reynolds RK, Lin J. Inhibition of constitutively active Stat3 suppresses growth of human ovarian and breast cancer cells. Oncogene 2001; 20:7925-34. [PMID: 11753675 DOI: 10.1038/sj.onc.1204990] [Citation(s) in RCA: 217] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2001] [Revised: 08/13/2001] [Accepted: 09/18/2001] [Indexed: 11/09/2022]
Abstract
Signal transducers and activators of transcription (STATs) are transcription factors activated in response to cytokines and growth factors. Constitutively active Stat3 has been shown to mediate oncogenic transformation in cultured cells and induce tumor formation in mice. An increasing number of tumor-derived cell lines as well as samples from human cancer have been reported to express constitutively active Stat3 protein. We previously demonstrated that ovarian cancer cell lines express high levels of constitutively active Stat3. In this study, we show that inhibition of the Stat3 signaling pathway using the Janus Kinase-selective inhibitor, AG490, and a dominant negative Stat3 (Stat3beta) significantly suppresses the growth of ovarian and breast cancer cell lines harboring constitutively active Stat3. In the ovarian cancer cell lines, AG490 also diminished the phosphorylation of Stat3, Stat3 DNA binding activity, and the expression of Bcl-x(L). Further, AG490 induced significant apoptosis in ovarian and breast cancer cell lines expressing high levels of constitutively active Stat3 but had a less profound effect on normal cells lacking constitutively active Stat3. AG490 also enhanced apoptosis induced by cisplatin in ovarian cancer cells. These results suggest that inhibition of Stat3 signaling may provide a potential therapeutic approach for treating ovarian and breast cancers.
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Rudd PM, Wormald MR, Stanfield RL, Huang M, Mattsson N, Speir JA, DiGennaro JA, Fetrow JS, Dwek RA, Wilson IA. Roles for glycosylation of cell surface receptors involved in cellular immune recognition. J Mol Biol 1999; 293:351-66. [PMID: 10529350 DOI: 10.1006/jmbi.1999.3104] [Citation(s) in RCA: 185] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The majority of cell surface receptors involved in antigen recognition by T cells and in the orchestration of the subsequent cell signalling events are glycoproteins. The length of a typical N-linked sugar is comparable with that of an immunoglobulin domain (30 A). Thus, by virtue of their size alone, oligosaccharides may be expected to play a significant role in the functions and properties of the cell surface proteins to which they are attached. A databank of oligosaccharide structures has been constructed from NMR and crystallographic data to aid in the interpretation of crystal structures of glycoproteins. As unambiguous electron density can usually only be assigned to the glycan cores, the remainder of the sugar is then modelled into the crystal lattice by superimposing the appropriate oligosaccharide from the database. This approach provides insights into the roles that glycosylation might play in cell surface receptors, by providing models that delineate potential close packing interactions on the cell surface. It has been proposed that the specific recognition of antigen by T cells results in the formation of an immunological synapse between the T cell and the antigen-presenting cell. The cell adhesion glycoproteins, such as CD2 and CD48, help to form a cell junction, providing a molecular spacer between opposing cells. The oligosaccharides located on the membrane proximal domains of CD2 and CD48 provide a scaffold to orient the binding faces, which leads to increased affinity. In the next step, recruitment of the peptide major histocompatibility complex (pMHC) by the T-cell receptors (TCRs) requires mobility on the membrane surface. The TCR sugars are located such that they could prevent non-specific aggregation. Importantly, the sugars limit the possible geometry and spacing of TCR/MHC clusters which precede cell signalling. We postulate that, in the final stage, the sugars could play a general role in controlling the assembly and stabilisation of the complexes in the synapse and in protecting them from proteolysis during prolonged T-cell engagement.
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Review |
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185 |
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Ernst P, Wang J, Huang M, Goodman RH, Korsmeyer SJ. MLL and CREB bind cooperatively to the nuclear coactivator CREB-binding protein. Mol Cell Biol 2001; 21:2249-58. [PMID: 11259575 PMCID: PMC86859 DOI: 10.1128/mcb.21.7.2249-2258.2001] [Citation(s) in RCA: 178] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A fragment of the mixed-lineage leukemia (MLL) gene (Mll, HRX, ALL-1) was identified in a yeast genetic screen designed to isolate proteins that interact with the CREB-CREB-binding protein (CBP) complex. When tested for binding to CREB or CBP individually, this MLL fragment interacted directly with CBP, but not with CREB. In vitro binding experiments refined the minimal region of interaction to amino acids 2829 to 2883 of MLL, a potent transcriptional activation domain, and amino acids 581 to 687 of CBP (the CREB-binding or KIX domain). The transactivation activity of MLL was dependent on CBP, as either adenovirus E1A expression, which inhibits CBP activity, or alteration of MLL residues important for CBP interaction proved effective at inhibiting MLL-mediated transactivation. Single amino acid substitutions within the MLL activation domain revealed that five hydrophobic residues, potentially forming a hydrophobic face of an amphipathic helix, were critical for the interaction of MLL with CBP. Using purified components, we found that the MLL activation domain facilitated the binding of CBP to phosphorylated CREB. In contrast with paradigms in which factors compete for limiting quantities of CBP, these results reveal that two distinct transcription factor activation domains can cooperatively target the same motif on CBP.
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178 |
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Graves LM, Guy HI, Kozlowski P, Huang M, Lazarowski E, Pope RM, Collins MA, Dahlstrand EN, Earp HS, Evans DR. Regulation of carbamoyl phosphate synthetase by MAP kinase. Nature 2000; 403:328-32. [PMID: 10659854 DOI: 10.1038/35002111] [Citation(s) in RCA: 160] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The de novo synthesis of pyrimidine nucleotides is required for mammalian cells to proliferate. The rate-limiting step in this pathway is catalysed by carbamoyl phosphate synthetase (CPS II), part of the multifunctional enzyme CAD. Here we describe the regulation of CAD by the mitogen-activated protein (MAP) kinase cascade. When phosphorylated by MAP kinase in vitro or activated by epidermal growth factor in vivo, CAD lost its feedback inhibition (which is dependent on uridine triphosphate) and became more sensitive to activation (which depends upon phosphoribosyl pyrophosphate). Both these allosteric regulatory changes favour biosynthesis of pyrimidines for growth. They were accompanied by increased epidermal growth factor-dependent phosphorylation of CAD in vivo and were prevented by inhibition of MAP kinase. Mutation of a consensus MAP kinase phosphorylation site abolished the changes in CAD allosteric regulation that were stimulated by growth factors. Finally, consistent with an effect of MAP kinase signalling on CPS II activity, epidermal growth factor increased cellular uridine triphosphate and this increase was reversed by inhibition of MAP kinase. Hence these studies may indicate a direct link between activation of the MAP kinase cascade and de novo biosynthesis of pyrimidine nucleotides.
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Huang M, Elledge SJ. Identification of RNR4, encoding a second essential small subunit of ribonucleotide reductase in Saccharomyces cerevisiae. Mol Cell Biol 1997; 17:6105-13. [PMID: 9315670 PMCID: PMC232460 DOI: 10.1128/mcb.17.10.6105] [Citation(s) in RCA: 154] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Ribonucleotide reductase (RNR), which catalyzes the rate-limiting step for deoxyribonucleotide production required for DNA synthesis, is an alpha2beta2 tetramer consisting of two large and two small subunits. RNR2 encodes a small subunit and is essential for mitotic viability in Saccharomyces cerevisiae. We have cloned a second essential gene encoding a homologous small subunit, RNR4. RNR4 and RNR2 appear to have nonoverlapping functions and cannot substitute for each other even when overproduced. The lethality of RNR4 deletion mutations can be suppressed by overexpression of RNR1 and RNR3, two genes encoding the large subunit of the RNR enzyme, indicating genetic interactions among the RNR genes. RNR2 and RNR4 may be present in the same reductase complex in vivo, since they coimmunoprecipitate from cell extracts. Like the other RNR genes, RNR4 is inducible by DNA-damaging agents through the same signal transduction pathway involving MEC1, RAD53, and DUN1 kinase genes. Analysis of DNA damage inducibility of RNR2 and RNR4 revealed partial inducibility in dun1 mutants, indicating a DUN1-independent branch of the transcriptional response to DNA damage.
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Huang M, Page C, Reynolds RK, Lin J. Constitutive activation of stat 3 oncogene product in human ovarian carcinoma cells. Gynecol Oncol 2000; 79:67-73. [PMID: 11006034 DOI: 10.1006/gyno.2000.5931] [Citation(s) in RCA: 154] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
OBJECTIVE Stat 3 functions in transducing signals from the cell's surface to its nucleus and activation of gene transcription. Aberrations of Stat 3 in breast cancer have raised the possibility of its contribution to oncogenesis. Our goal was to examine ovarian cancer cell lines to determine whether Stat 3 plays a relevant role in ovarian carcinogenesis. METHODS Protein lysates were extracted from normal ovarian surface epithelial cells and malignant cells. Western blotting techniques were performed with phosphorylation-independent or phosphorylation-specific Stat 3 (tyrosine 705) antibody. Confirmation of Stat 3 activation was determined by a luciferase reporter driven by a promoter containing Stat 3-specific binding sites. Bcl-x(L) and cyclin D(1) were also analyzed by Western blotting. RESULTS MDAH 2774, OV-1063, Caov-3, and O.C. 22819 expressed high levels of phosphorylated Stat 3. In contrast, A2780 and normal ovarian surface epithelial cells had little Stat 3 phosphorylation recognized. Confirmation of persistent activation of Stat 3 activity was shown by transfection of cells with a Stat 3 luciferase reporter. Potential downstream mediators of Stat 3 including Bcl-x(L) and cyclin D(1) were also evaluated. In cells expressing activated Stat 3, high levels of both Bcl-x(L) and cyclin D(1) were detected, whereas in A2780 cells, which did not express activated Stat 3, only low levels of Bcl-x(L) and cyclin D(1) were expressed. CONCLUSIONS Constitutive activation of Stat 3 is present in ovarian cancer lines but not in normal ovarian surface epithelial cells. Activation of Stat 3 is a common event during oncogenic transformation upstream to both Bcl-x(L) and cyclin D(1). The relationship of this aberrancy of ovarian carcinoma harboring activated Stat 3 deserves further investigation.
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Nichols WG, Corey L, Gooley T, Drew WL, Miner R, Huang M, Davis C, Boeckh M. Rising pp65 antigenemia during preemptive anticytomegalovirus therapy after allogeneic hematopoietic stem cell transplantation: risk factors, correlation with DNA load, and outcomes. Blood 2001; 97:867-74. [PMID: 11159510 DOI: 10.1182/blood.v97.4.867] [Citation(s) in RCA: 153] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To determine the risk factors and outcomes associated with rising cytomegalovirus (CMV) antigenemia levels during preemptive therapy among stem cell allograft recipients, 119 patients with CMV antigenemia were studied. Patients were prospectively monitored for CMV antigenemia weekly; those with positive findings on antigenemia tests were treated with intravenous ganciclovir (5 mg/kg twice daily for 1 week, followed by 5 mg/kg per day for 5-6 d/wk). While on therapy, 47 of 119 (39%) patients demonstrated increases that were 2 or more times greater than their baseline values, whereas 33 of 119 (28%) patients demonstrated increases that were 5 or more times greater. Rising antigenemia was confirmed by polymerase chain reaction for CMV DNA. Multivariate analysis identified corticosteroids as the primary risk factor for increasing antigenemia: for increases greater than or equal to twice the baseline, 1 to 2 mg/kg steroids was associated with an odds ratio (OR) of 4.0. For increases greater than or equal to 2 mg/kg steroids, the OR was 10.1. CMV isolates obtained at the time of rising antigenemia were susceptible to ganciclovir, indicating that resistance was not a major factor. Overall, rising antigenemia levels were not correlated with CMV disease. All 4 patients in whom CMV disease developed during therapy, however, had rising antigenemia levels. Among the 47 patients with antigenemia increases greater than or equal to twice the baseline, 15 were re-induced with antivirals, whereas 32 continued to receive maintenance therapy. All 4 patients in whom CMV disease developed during therapy received maintenance therapy, and 3 died with CMV disease. Thus, host factors such as the receipt of corticosteroids explain increasing viral load during the early phase of preemptive therapy. Continued induction dosing or re-induction may protect against early breakthrough CMV disease and CMV-related death among patients with rising antigenemia on preemptive therapy. (Blood. 2001;97:867-874)
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Walkley SU, Thrall MA, Dobrenis K, Huang M, March PA, Siegel DA, Wurzelmann S. Bone marrow transplantation corrects the enzyme defect in neurons of the central nervous system in a lysosomal storage disease. Proc Natl Acad Sci U S A 1994; 91:2970-4. [PMID: 8159689 PMCID: PMC43496 DOI: 10.1073/pnas.91.8.2970] [Citation(s) in RCA: 148] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Neuronal storage disorders are fatal neurodegenerative diseases of humans and animals that are caused by inherited deficiencies of lysosomal hydrolase activity. Affected individuals often appear normal at birth but eventually develop progressive neurologic symptoms including sensory and motor deficits, mental retardation, and seizures. We have examined efficacy of bone marrow transplantation as a means of enzyme replacement, using cats with the lysosomal storage disease alpha-mannosidosis. Treated animals showed little or no progression of neurologic signs 1-2 years after transplant, whereas untreated cats became severely impaired and reached endstage disease by 6 months of age. Increased lysosomal alpha-mannosidase activity was found in brain tissue of the treated animals, and electron microscopy revealed no evidence of lysosomal storage within most neurons. Histochemical localization of acidic alpha-D-mannoside mannohydrolase (EC 3.2. 1.24), using 5-bromo-4-chloro-3-indolyl alpha-D-mannopyranoside, showed that functional enzyme was present in neurons, glial cells, and cells associated with blood vessels. This study provides direct evidence that bone marrow transplantation as treatment for a neuronal storage disease can lead to significant levels of a missing lysosomal hydrolase within neurons of the central nervous system and to compensation for the genetic metabolic defect.
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Lyman GH, Dale DC, Culakova E, Poniewierski MS, Wolff DA, Kuderer NM, Huang M, Crawford J. The impact of the granulocyte colony-stimulating factor on chemotherapy dose intensity and cancer survival: a systematic review and meta-analysis of randomized controlled trials. Ann Oncol 2013; 24:2475-2484. [PMID: 23788754 DOI: 10.1093/annonc/mdt226] [Citation(s) in RCA: 146] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND The granulocyte colony-stimulating factor (G-CSF) is utilized to reduce neutropenic complications in patients receiving cancer chemotherapy. This study represents a systematic review and evidence summary of the impact of G-CSF support on chemotherapy dose intensity and overall mortality. MATERIALS AND METHODS All randomized controlled trials (RCTs) comparing chemotherapy with or without G-CSF support and reporting all-cause mortality with at least 2 years of follow-up were sought. Dual-blind data abstraction of disease, treatment, patient and outcome study results with conflict resolution by third party was carried out. RESULTS The search revealed 61 randomized comparisons of chemotherapy with or without initial G-CSF support. Death was reported in 4251 patients randomized to G-CSFs and in 5188 controls. Relative risk (RR) with G-CSF support for all-cause mortality was 0.93 (95% confidence interval: 0.90-0.96; P < 0.001). RR for mortality varied by intended chemotherapy dose and schedule: same dose and schedule (RR = 0.96; P = 0.060), dose dense (RR = 0.89; P < 0.001), dose escalation (RR = 0.92; P = 0.019) and drug substitution or addition (RR = 0.94; P = 0.003). Greater RR reduction was observed among studies with longer follow-up (P = 0.02), where treatment was for curative intent (RR = 0.91; P < 0.001), and where survival was the primary outcome (RR = 0.91; P < 0.001). CONCLUSIONS All-cause mortality is reduced in patients receiving chemotherapy with primary G-CSF support. The greatest impact was observed in RCTs in patients receiving dose-dense schedules.
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Systematic Review |
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Schalk I, Zeng K, Wu SK, Stura EA, Matteson J, Huang M, Tandon A, Wilson IA, Balch WE. Structure and mutational analysis of Rab GDP-dissociation inhibitor. Nature 1996; 381:42-8. [PMID: 8609986 DOI: 10.1038/381042a0] [Citation(s) in RCA: 140] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The crystal structure of the bovine alpha-isoform of Rab GDP-dissociation inhibitor (GDI), which functions in vesicle-membrane transport to recycle and regulate Rab GTPases, has been determined to a resolution of 1.81 A. GDI is constructed of two main structural units, a large complex multisheet domain I and a smaller alpha-helical domain II. The structural organization of domain I is surprisingly closely related to FAD-containing monooxygenases and oxidases. Sequence-conserved regions common to GDI and the choroideraemia gene product, which delivers Rab to catalytic subunits of Rab geranylgeranyltransferase II, are clustered on one face of the molecule. The two most sequence-conserved regions, which form a compact structure at the apex of GDI, are shown by site-directed mutagenesis to play a critical role in the binding of Rab proteins.
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Huang M, Weissman JT, Beraud-Dufour S, Luan P, Wang C, Chen W, Aridor M, Wilson IA, Balch WE. Crystal structure of Sar1-GDP at 1.7 A resolution and the role of the NH2 terminus in ER export. J Cell Biol 2001; 155:937-48. [PMID: 11739406 PMCID: PMC2150902 DOI: 10.1083/jcb.200106039] [Citation(s) in RCA: 136] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2001] [Revised: 10/17/2001] [Accepted: 10/17/2001] [Indexed: 11/22/2022] Open
Abstract
The Sar1 GTPase is an essential component of COPII vesicle coats involved in export of cargo from the ER. We report the 1.7-A structure of Sar1 and find that consistent with the sequence divergence of Sar1 from Arf family GTPases, Sar1 is structurally distinct. In particular, we show that the Sar1 NH2 terminus contains two regions: an NH2-terminal extension containing an evolutionary conserved hydrophobic motif that facilitates membrane recruitment and activation by the mammalian Sec12 guanine nucleotide exchange factor, and an alpha1' amphipathic helix that contributes to interaction with the Sec23/24 complex that is responsible for cargo selection during ER export. We propose that the hydrophobic Sar1 NH2-terminal activation/recruitment motif, in conjunction with the alpha1' helix, mediates the initial steps in COPII coat assembly for export from the ER.
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Huang M, Daly JW. Adenosine-elicited accumulation of cyclic AMP in brain slices: potentiation by agents which inhibit uptake of adenosine. Life Sci 1974; 14:489-503. [PMID: 4363081 DOI: 10.1016/0024-3205(74)90364-6] [Citation(s) in RCA: 134] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Loeb KR, Jerome KR, Goddard J, Huang M, Cent A, Corey L. High-throughput quantitative analysis of hepatitis B virus DNA in serum using the TaqMan fluorogenic detection system. Hepatology 2000; 32:626-9. [PMID: 10960459 DOI: 10.1053/jhep.2000.9878] [Citation(s) in RCA: 133] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
Abstract
Reproducible quantitative assays to detect viral nucleic acids have proven useful in defining disease progression and following response to therapy in a wide variety of viral infections. We describe the development of a quantitative assay to detect hepatitis B virus (HBV) DNA using real-time fluorescent-probe polymerase chain reaction (PCR) (TaqMan). The assay is highly reproducible, highly automated, and much more sensitive than the currently used branched-chain DNA (bDNA) assay for HBV. The quantitative PCR assay accurately detected samples ranging from 10 to 10(9) copies of HBV DNA per milliliter. Of 157 serum samples submitted for HBV quantitation, 119 were positive by TaqMan PCR versus only 55 by bDNA (P <.001). All 55 bDNA-positives were positive by TaqMan. Of the 77 samples with detectable HBV-DNA titers below 3.75 x 10(5) copies by TaqMan, only 13 were detected by bDNA. We tested 119 patients negative for all HBV serologic markers, and all tested negative in the TaqMan assay. HBV DNA was detected by TaqMan in 164 of 195 (84%) of hepatitis B surface antigen (HBsAg)-positive samples. Among hepatitis B e antigen (HBeAg)-positive samples, median titers were 4. 3 x 10(6) copies/mL versus 322 copies/mL in HBeAg-negative samples (P =.012). The TaqMan assay for HBV DNA is highly sensitive and reproducible and thus appears useful in accurately defining levels of viral replication among persons with HBV infection.
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