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Jonnalagadda US, Su X, Kwan JJ. Nanostructured TiO 2 cavitation agents for dual-modal sonophotocatalysis with pulsed ultrasound. Ultrason Sonochem 2021; 73:105530. [PMID: 33799108 PMCID: PMC8044705 DOI: 10.1016/j.ultsonch.2021.105530] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Revised: 03/06/2021] [Accepted: 03/12/2021] [Indexed: 05/08/2023]
Abstract
Current sonochemical methods rely on spatially uncontrolled cavitation for radical species generation to promote chemical reactions. To improve radical generation, sonosensitizers have been demonstrated to be activated by cavitation-based light emission (sonoluminescence). Unfortunately, this process remains relatively inefficient compared to direct photocatalysis, due to the physical separation between cavitation event and sonosensitizing agent. In this study, we have synthesized nanostructured titanium dioxide particles to couple the source for cavitation within a photocatalytic site to create a sonophotocatalyst. In doing so, we demonstrate that site-controlled cavitation from the nanoparticles using pulsed ultrasound at reduced acoustic powers resulted in the sonochemical degradation methylene blue at rates nearly three orders of magnitude faster than other titanium dioxide-based nanoparticles by conventional methods. Sonochemical degradation was directly proportional to the measured cavitation produced by these sonophotocatalysts. Our work suggests that simple nanostructuring of current sonosensitizers to enable on-site cavitation greatly enhances sonochemical reaction rates.
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Affiliation(s)
- U S Jonnalagadda
- School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, 637459, Singapore
| | - X Su
- School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, 637459, Singapore
| | - J J Kwan
- Department of Engineering Science, University of Oxford, Oxford OX1 3PJ, United Kingdom.
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2
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Mair B, Tomic J, Masud SN, Tonge P, Weiss A, Usaj M, Tong AHY, Kwan JJ, Brown KR, Titus E, Atkins M, Chan KSK, Munsie L, Habsid A, Han H, Kennedy M, Cohen B, Keller G, Moffat J. Essential Gene Profiles for Human Pluripotent Stem Cells Identify Uncharacterized Genes and Substrate Dependencies. Cell Rep 2020; 27:599-615.e12. [PMID: 30970261 DOI: 10.1016/j.celrep.2019.02.041] [Citation(s) in RCA: 55] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 12/24/2018] [Accepted: 02/11/2019] [Indexed: 12/20/2022] Open
Abstract
Human pluripotent stem cells (hPSCs) provide an invaluable tool for modeling diseases and hold promise for regenerative medicine. For understanding pluripotency and lineage differentiation mechanisms, a critical first step involves systematically cataloging essential genes (EGs) that are indispensable for hPSC fitness, defined as cell reproduction in this study. To map essential genetic determinants of hPSC fitness, we performed genome-scale loss-of-function screens in an inducible Cas9 H1 hPSC line cultured on feeder cells and laminin to identify EGs. Among these, we found FOXH1 and VENTX, genes that encode transcription factors previously implicated in stem cell biology, as well as an uncharacterized gene, C22orf43/DRICH1. hPSC EGs are substantially different from other human model cell lines, and EGs in hPSCs are highly context dependent with respect to different growth substrates. Our CRISPR screens establish parameters for genome-wide screens in hPSCs, which will facilitate the characterization of unappreciated genetic regulators of hPSC biology.
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Affiliation(s)
- Barbara Mair
- Donnelly Centre, University of Toronto, Toronto, ON, Canada
| | - Jelena Tomic
- Donnelly Centre, University of Toronto, Toronto, ON, Canada
| | - Sanna N Masud
- Donnelly Centre, University of Toronto, Toronto, ON, Canada; Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Peter Tonge
- Centre for Commercialization of Regenerative Medicine, Toronto, ON, Canada
| | | | - Matej Usaj
- Donnelly Centre, University of Toronto, Toronto, ON, Canada
| | | | - Jamie J Kwan
- McEwen Stem Cell Institute, University Health Network, University of Toronto, Toronto, ON, Canada; Princess Margaret Cancer Centre, University Health Network, University of Toronto, Toronto, ON, Canada
| | - Kevin R Brown
- Donnelly Centre, University of Toronto, Toronto, ON, Canada
| | - Emily Titus
- Centre for Commercialization of Regenerative Medicine, Toronto, ON, Canada
| | - Michael Atkins
- McEwen Stem Cell Institute, University Health Network, University of Toronto, Toronto, ON, Canada; Princess Margaret Cancer Centre, University Health Network, University of Toronto, Toronto, ON, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
| | | | - Lise Munsie
- Centre for Commercialization of Regenerative Medicine, Toronto, ON, Canada
| | - Andrea Habsid
- Donnelly Centre, University of Toronto, Toronto, ON, Canada
| | - Hong Han
- Donnelly Centre, University of Toronto, Toronto, ON, Canada
| | - Marion Kennedy
- McEwen Stem Cell Institute, University Health Network, University of Toronto, Toronto, ON, Canada; Princess Margaret Cancer Centre, University Health Network, University of Toronto, Toronto, ON, Canada
| | - Brenda Cohen
- McEwen Stem Cell Institute, University Health Network, University of Toronto, Toronto, ON, Canada; Princess Margaret Cancer Centre, University Health Network, University of Toronto, Toronto, ON, Canada
| | - Gordon Keller
- McEwen Stem Cell Institute, University Health Network, University of Toronto, Toronto, ON, Canada; Princess Margaret Cancer Centre, University Health Network, University of Toronto, Toronto, ON, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
| | - Jason Moffat
- Donnelly Centre, University of Toronto, Toronto, ON, Canada; Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada; Canadian Institute for Advanced Research, Toronto, ON, Canada; Institute for Biomaterials and BioMedical Engineering, University of Toronto, ON, Canada.
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3
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Smirnova E, Kwan JJ, Siu R, Gao X, Zoidl G, Demeler B, Saridakis V, Donaldson LW. A new mode of SAM domain mediated oligomerization observed in the CASKIN2 neuronal scaffolding protein. Cell Commun Signal 2016; 14:17. [PMID: 27549312 PMCID: PMC4994250 DOI: 10.1186/s12964-016-0140-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Accepted: 08/12/2016] [Indexed: 11/18/2022] Open
Abstract
Background CASKIN2 is a homolog of CASKIN1, a scaffolding protein that participates in a signaling network with CASK (calcium/calmodulin-dependent serine kinase). Despite a high level of homology between CASKIN2 and CASKIN1, CASKIN2 cannot bind CASK due to the absence of a CASK Interaction Domain and consequently, may have evolved undiscovered structural and functional distinctions. Results We demonstrate that the crystal structure of the Sterile Alpha Motif (SAM) domain tandem (SAM1-SAM2) oligomer from CASKIN2 is different than CASKIN1, with the minimal repeating unit being a dimer, rather than a monomer. Analytical ultracentrifugation sedimentation velocity methods revealed differences in monomer/dimer equilibria across a range of concentrations and ionic strengths for the wild type CASKIN2 SAM tandem and a structure-directed double mutant that could not oligomerize. Further distinguishing CASKIN2 from CASKIN1, EGFP-tagged SAM tandem proteins expressed in Neuro2a cells produced punctae that were distinct both in shape and size. Conclusions This study illustrates a new way in which neuronal SAM domains can assemble into large macromolecular assemblies that might concentrate and amplify synaptic responses. Electronic supplementary material The online version of this article (doi:10.1186/s12964-016-0140-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Ekaterina Smirnova
- Department of Biology, York University, 4700 Keele Street, Toronto, ON, M3J 1P3, Canada
| | - Jamie J Kwan
- Department of Biology, York University, 4700 Keele Street, Toronto, ON, M3J 1P3, Canada
| | - Ryan Siu
- Department of Biology, York University, 4700 Keele Street, Toronto, ON, M3J 1P3, Canada
| | - Xin Gao
- Division of Computer, Computational Bioscience Research Center, Electrical and Mathematical Science and Engineering, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Kingdom of Saudi Arabia
| | - Georg Zoidl
- Department of Biology, York University, 4700 Keele Street, Toronto, ON, M3J 1P3, Canada.,Department of Psychology, York University, 4700 Keele Street, Toronto, ON, M3J 1P3, Canada
| | - Borries Demeler
- Department of Biochemistry, University of Texas Health Science Center at San Antonio, 7760 Floyd Curl Drive, San Antonio, TX, 78229-3900, USA
| | - Vivian Saridakis
- Department of Biology, York University, 4700 Keele Street, Toronto, ON, M3J 1P3, Canada
| | - Logan W Donaldson
- Department of Biology, York University, 4700 Keele Street, Toronto, ON, M3J 1P3, Canada.
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4
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Ramsook SN, Ni J, Shahangian S, Vakiloroayaei A, Khan N, Kwan JJ, Donaldson LW. A Model for Dimerization of the SOX Group E Transcription Factor Family. PLoS One 2016; 11:e0161432. [PMID: 27532129 PMCID: PMC4988710 DOI: 10.1371/journal.pone.0161432] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Accepted: 08/07/2016] [Indexed: 11/19/2022] Open
Abstract
Group E members of the SOX transcription factor family include SOX8, SOX9, and SOX10. Preceding the high mobility group (HMG) domain in each of these proteins is a thirty-eight amino acid region that supports the formation of dimers on promoters containing tandemly inverted sites. The purpose of this study was to obtain new structural insights into how the dimerization region functions with the HMG domain. From a mutagenic scan of the dimerization region, the most essential amino acids of the dimerization region were clustered on the hydrophobic face of a single, predicted amphipathic helix. Consistent with our hypothesis that the dimerization region directly contacts the HMG domain, a peptide corresponding to the dimerization region bound a preassembled HMG-DNA complex. Sequence conservation among Group E members served as a basis to identify two surface exposed amino acids in the HMG domain of SOX9 that were necessary for dimerization. These data were combined to make a molecular model that places the dimerization region of one SOX9 protein onto the HMG domain of another SOX9 protein situated at the opposing site of a tandem promoter. The model provides a detailed foundation for assessing the impact of mutations on SOX Group E transcription factors.
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Affiliation(s)
| | - Joyce Ni
- Department of Biology, York University, Toronto, ON, Canada
| | | | | | - Naveen Khan
- Department of Biology, York University, Toronto, ON, Canada
| | - Jamie J. Kwan
- Department of Biology, York University, Toronto, ON, Canada
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5
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Kwan JJ, Graham S, Myers R, Carlisle R, Stride E, Coussios CC. Ultrasound-induced inertial cavitation from gas-stabilizing nanoparticles. Phys Rev E Stat Nonlin Soft Matter Phys 2015; 92:023019. [PMID: 26382515 DOI: 10.1103/physreve.92.023019] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2015] [Indexed: 05/05/2023]
Abstract
The understanding of cavitation from nanoparticles has been hindered by the inability to control nanobubble size. We present a method to manufacture nanoparticles with a tunable single hemispherical depression (nanocups) of mean diameter 90, 260, or 650 nm entrapping a nanobubble. A modified Rayleigh-Plesset crevice model predicts the inertial cavitation threshold as a function of cavity size and frequency, and is verified experimentally. The ability to tune cavitation nanonuclei and predict their behavior will be useful for applications ranging from cancer therapy to ultrasonic cleaning.
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Affiliation(s)
- J J Kwan
- Institute of Biomedical Engineering, University of Oxford, Oxford OX3 7DQ, United Kingdom
| | - S Graham
- Institute of Biomedical Engineering, University of Oxford, Oxford OX3 7DQ, United Kingdom
| | - R Myers
- Institute of Biomedical Engineering, University of Oxford, Oxford OX3 7DQ, United Kingdom
| | - R Carlisle
- Institute of Biomedical Engineering, University of Oxford, Oxford OX3 7DQ, United Kingdom
| | - E Stride
- Institute of Biomedical Engineering, University of Oxford, Oxford OX3 7DQ, United Kingdom
| | - C C Coussios
- Institute of Biomedical Engineering, University of Oxford, Oxford OX3 7DQ, United Kingdom
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6
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Smirnova E, Shanbhag R, Kurabi A, Mobli M, Kwan JJ, Donaldson LW. Solution structure and peptide binding of the PTB domain from the AIDA1 postsynaptic signaling scaffolding protein. PLoS One 2013; 8:e65605. [PMID: 23799029 PMCID: PMC3683042 DOI: 10.1371/journal.pone.0065605] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2013] [Accepted: 04/30/2013] [Indexed: 11/18/2022] Open
Abstract
AIDA1 links persistent chemical signaling events occurring at the neuronal synapse with global changes in gene expression. Consistent with its role as a scaffolding protein, AIDA1 is composed of several protein-protein interaction domains. Here we report the NMR structure of the carboxy terminally located phosphotyrosine binding domain (PTB) that is common to all AIDA1 splice variants. A comprehensive survey of peptides identified a consensus sequence around an NxxY motif that is shared by a number of related neuronal signaling proteins. Using peptide arrays and fluorescence based assays, we determined that the AIDA1 PTB domain binds amyloid protein precursor (APP) in a similar manner to the X11/Mint PTB domain, albeit at reduced affinity (∼10 µM) that may allow AIDA1 to effectively sample APP, as well as other protein partners in a variety of cellular contexts.
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Affiliation(s)
| | - Riya Shanbhag
- Department of Biology, York University, Toronto, Ontario, Canada
| | - Arwa Kurabi
- Department of Biology, York University, Toronto, Ontario, Canada
| | - Mehdi Mobli
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Jamie J. Kwan
- Department of Biology, York University, Toronto, Ontario, Canada
| | - Logan W. Donaldson
- Department of Biology, York University, Toronto, Ontario, Canada
- * E-mail:
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7
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Kwan JJ, Smirnova E, Khazai S, Evanics F, Maxwell KL, Donaldson LW. The solution structures of two prophage homologues of the bacteriophage λ Ea8.5 protein reveal a newly discovered hybrid homeodomain/zinc-finger fold. Biochemistry 2013; 52:3612-4. [PMID: 23672713 DOI: 10.1021/bi400543w] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A cluster of genes in the exoxis region of bacteriophage λ are capable of inhibiting the initiation of DNA synthesis in Escherichia coli. The most indispensible gene in this region is ea8.5. Here, we report the nuclear magnetic resonance structures of two ea8.5 orthologs from enteropathogenic E. coli and Pseudomonas putida prophages. Both proteins are characterized by a fused homeodomain/zinc-finger fold that escaped detection by primary sequence search methods. While these folds are both associated with a nucleic acid binding function, the amino acid composition suggests otherwise, leading to the possibility that Ea8.5 associates with other viral and host proteins.
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Affiliation(s)
- Jamie J Kwan
- Department of Biology, York University , 4700 Keele Street, Toronto, ON M3J1P3, Canada
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8
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Kurabi A, Brener S, Mobli M, Kwan JJ, Donaldson LW. A Nuclear Localization Signal at the SAM–SAM Domain Interface of AIDA-1 Suggests a Requirement for Domain Uncoupling Prior to Nuclear Import. J Mol Biol 2009; 392:1168-77. [DOI: 10.1016/j.jmb.2009.08.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2009] [Revised: 08/04/2009] [Accepted: 08/04/2009] [Indexed: 01/08/2023]
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9
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Edmonds L, Liu A, Kwan JJ, Avanessy A, Caracoglia M, Yang I, Maxwell KL, Rubenstein J, Davidson AR, Donaldson LW. The NMR structure of the gpU tail-terminator protein from bacteriophage lambda: identification of sites contributing to Mg(II)-mediated oligomerization and biological function. J Mol Biol 2006; 365:175-86. [PMID: 17056065 DOI: 10.1016/j.jmb.2006.09.068] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2006] [Revised: 09/20/2006] [Accepted: 09/25/2006] [Indexed: 11/29/2022]
Abstract
During the late stages of lambda bacteriophage assembly, the protein gpU terminates tail polymerization and participates at the interface between the mature capsid and tail components. When it engages the lambda tail, gpU undergoes a monomer-hexamer transition to achieve its biologically active form. Towards understanding how gpU participates in multiple protein-protein interactions, we have solved the structure of gpU in its monomeric state using NMR methods. The structure reveals a mixed alpha/beta motif with several dynamic loops at the periphery. Addition of 20 mM MgCl(2) is known to oligomerize gpU in the absence of its protein partners. Multiple image analysis of electron micrographs revealed ring-like structures of magnesium ion saturated gpU with a 30 A pore, consistent with its function as a portal for the passage of viral DNA into the host bacterium. The ability of magnesium ions to promote oligomerization was lost when substitutions were made at a cluster of acidic amino acids in the vicinity of helix alpha2 and the beta1-beta2 loop. Furthermore, substitutions at these sites abolished the biological activity of gpU.
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Affiliation(s)
- Lizbeth Edmonds
- Department of Biology, York University, 4700 Keele Street, Canada M3J 1P3
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Kwan JJ, Warner N, Maini J, Chan Tung KW, Zakaria H, Pawson T, Donaldson LW. Saccharomyces cerevisiae Ste50 Binds the MAPKKK Ste11 Through a Head-to-tail SAM Domain Interaction. J Mol Biol 2006; 356:142-54. [PMID: 16337230 DOI: 10.1016/j.jmb.2005.11.012] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2005] [Revised: 10/27/2005] [Accepted: 11/03/2005] [Indexed: 10/25/2022]
Abstract
In Saccharomyces cerevisiae, signal transduction through pathways governing mating, osmoregulation, and nitrogen starvation depends upon a direct interaction between the sterile alpha motif (SAM) domains of the Ste11 mitogen-activated protein kinase kinase kinase (MAPKKK) and its regulator Ste50. Previously, we solved the NMR structure of the SAM domain from Ste11 and identified two mutants that diminished binding to the Ste50 SAM domain. Building upon the Ste11 study, we present the NMR structure of the monomeric Ste50 SAM domain and a series of mutants bearing substitutions at surface-exposed hydrophobic amino acid residues. The mid-loop (ML) region of Ste11-SAM, defined by helices H3 and H4 and the end-helix (EH) region of Ste50-SAM, defined by helix H5, were sensitive to substitution, indicating that these two surfaces contribute to the high-affinity interaction. The combination of two mutants, Ste11-SAM-L72R and Ste50-SAM-L69R, formed a high-affinity heterodimer unencumbered by competing homotypic interactions that had prevented earlier NMR studies of the wild-type complex. Yeast bearing mutations that prevented the heterotypic Ste11-Ste50 association in vitro presented signaling defects in the mating and high-osmolarity growth pathways.
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Affiliation(s)
- Jamie J Kwan
- Department of Biology, York University, 4700 Keele Street, Toronto, Ont., Canada M3J 1P3
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11
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Aviv T, Amborski AN, Zhao XS, Kwan JJ, Johnson PE, Sicheri F, Donaldson LW. The NMR and X-ray structures of the Saccharomyces cerevisiae Vts1 SAM domain define a surface for the recognition of RNA hairpins. J Mol Biol 2005; 356:274-9. [PMID: 16375924 DOI: 10.1016/j.jmb.2005.11.066] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2005] [Revised: 10/23/2005] [Accepted: 11/21/2005] [Indexed: 10/25/2022]
Abstract
The SAM domain of the Saccharomyces cerevisiae post-transcriptional regulator Vts1 has a high affinity towards RNA hairpins containing a CUGGC pentaloop. We present the 1.6 Angstroms X-ray crystal structure of the Vts1 SAM domain in its unliganded state, and the NMR solution structure of this domain in its RNA-bound state. Both structures reveal a canonical five helix SAM domain flanked by additional secondary structural elements at the N and C termini. The two structures are essentially identical, implying that no major structural rearrangements occur upon RNA binding. Amide chemical shift changes map the RNA-binding site to a shallow, basic patch at the junction of helix alpha5 and the loop connecting helices alpha1 and alpha2.
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Affiliation(s)
- Tzvi Aviv
- Program in Molecular Biology and Cancer, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ont., Canada
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12
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Choi SW, Benzie IFF, Lam CSY, Chat SWS, Lam J, Yiu CH, Kwan JJ, Tang YH, Yeung GSP, Yeung VTF, Woo GC, Hannigan BM, Strain JJ. Inter-relationships between DNA damage, ascorbic acid and glycaemic control in Type 2 diabetes mellitus. Diabet Med 2005; 22:1347-53. [PMID: 16176195 DOI: 10.1111/j.1464-5491.2005.01647.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
AIMS The onset of complications in Type 2 diabetes mellitus (DM) patients cannot be predicted in individuals. Evidence suggests a link between complications and hyperglycaemia, oxidative stress and antioxidants, but causality is unclear. This study investigated baseline (entry) fasting plasma ascorbic acid, lymphocytic DNA damage and glycaemic control in Type 2 DM as part of a long-term study, the aim of which is to explore a biomarker profiling approach to identify and improve outcome in high-risk subjects. METHODS A cross-sectional study, in which DNA damage, glycated haemoglobin (HbA(1c)), fasting plasma glucose (FPG) and ascorbic acid (AA) were measured on fasting blood samples collected from 427 Type 2 DM subjects. RESULTS DNA damage was significantly (P < 0.0001) and directly correlated to both FPG (r = 0.540) and HbA(1c) (r = 0.282), and was significantly (P < 0.0001), independently and inversely correlated to plasma AA (r = -0.449). In those subjects with both poor glycaemic control and low AA (< 48 microm, the overall mean value for the study group), DNA damage was significantly (P < 0.005) higher compared with those subjects with a similar degree of hyperglycaemia but with AA above the mean. CONCLUSIONS The novel finding of a significant inverse relationship between plasma AA and DNA damage in Type 2 DM indicates that poorly controlled diabetic subjects might benefit from increased dietary vitamin C. The data also have important implications for biomarker profiling to identify those subjects who might benefit most from intensive therapy. Longer-term follow-up is underway.
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Affiliation(s)
- S W Choi
- Faculty of Health and Social Sciences, The Hong Kong Polytechnic University, Kowloon, Hong Kong
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13
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Kwan JJ, Warner N, Pawson T, Donaldson LW. The solution structure of the S.cerevisiae Ste11 MAPKKK SAM domain and its partnership with Ste50. J Mol Biol 2004; 342:681-93. [PMID: 15327964 DOI: 10.1016/j.jmb.2004.06.064] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2004] [Revised: 06/22/2004] [Accepted: 06/22/2004] [Indexed: 11/24/2022]
Abstract
Ste11 is a MAPKKK from Saccharomyces cerevisiae that helps mediate the response to mating pheromone and the ability to thrive in high-salt environments. These diverse functions are facilitated by a direct interaction between the SAM domain of Ste11 with the SAM domain of its regulatory partner, Ste50. We have solved the NMR structure of the Ste11 SAM domain (PDB 1OW5), which reveals a compact, five alpha-helix bundle and a high degree of structural similarity to the Polyhomeotic SAM domain. The combined study of Ste11 SAM rotational correlation times and crosslinking to Ste50-SAM has suggested a mode through which Ste11-SAM oligomerizes and selectively associates with Ste50-SAM. To probe homotypic and heterotypic interations, Ste11-SAM variants each containing a substitution of a surface-exposed hydrophobic residue were constructed. An I59R variant of Ste11-SAM, disrupted binding to Ste50-SAM in vitro. Yeast expressing full-length Ste11-I59R could neither respond to mating pheromone nor thrive in high salt media-demonstrating that the interaction between Ste11 and Ste50 SAM domains is a prerequisite for key signal transduction events.
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Affiliation(s)
- Jamie J Kwan
- Department of Biology, York University, 4700 Keele Street, Toronto, Ontario, Canada M3J 1P3
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