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Zhong R, Zhou D, Phillips DR, Adams ER, Chen L, Rose JP, Wang BC, Ye ZH. A rice GT61 glycosyltransferase possesses dual activities mediating 2-O-xylosyl and 2-O-arabinosyl substitutions of xylan. Planta 2024; 259:115. [PMID: 38589536 DOI: 10.1007/s00425-024-04396-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Accepted: 03/19/2024] [Indexed: 04/10/2024]
Abstract
MAIN CONCLUSION A member of the rice GT61 clade B is capable of transferring both 2-O-xylosyl and 2-O-arabinosyl residues onto xylan and another member specifically catalyses addition of 2-O-xylosyl residue onto xylan. Grass xylan is substituted predominantly with 3-O-arabinofuranose (Araf) as well as with some minor side chains, such as 2-O-Araf and 2-O-(methyl)glucuronic acid [(Me)GlcA]. 3-O-Arabinosylation of grass xylan has been shown to be catalysed by grass-expanded clade A members of the glycosyltransferase family 61. However, glycosyltransferases mediating 2-O-arabinosylation of grass xylan remain elusive. Here, we performed biochemical studies of two rice GT61 clade B members and found that one of them was capable of transferring both xylosyl (Xyl) and Araf residues from UDP-Xyl and UDP-Araf, respectively, onto xylooligomer acceptors, whereas the other specifically catalysed Xyl transfer onto xylooligomers, indicating that the former is a xylan xylosyl/arabinosyl transferase (named OsXXAT1 herein) and the latter is a xylan xylosyltransferase (named OsXYXT2). Structural analysis of the OsXXAT1- and OsXYXT2-catalysed reaction products revealed that the Xyl and Araf residues were transferred onto O-2 positions of xylooligomers. Furthermore, we demonstrated that OsXXAT1 and OsXYXT2 were able to substitute acetylated xylooligomers, but only OsXXAT1 could xylosylate GlcA-substituted xylooligomers. OsXXAT1 and OsXYXT2 were predicted to adopt a GT-B fold structure and molecular docking revealed candidate amino acid residues at the predicted active site involved in binding of the nucleotide sugar donor and the xylohexaose acceptor substrates. Together, our results establish that OsXXAT1 is a xylan 2-O-xylosyl/2-O-arabinosyl transferase and OsXYXT2 is a xylan 2-O-xylosyltransferase, which expands our knowledge of roles of the GT61 family in grass xylan synthesis.
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Affiliation(s)
- Ruiqin Zhong
- Department of Plant Biology, University of Georgia, Athens, GA, 30602, USA
| | - Dayong Zhou
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA
| | - Dennis R Phillips
- Department of Chemistry, University of Georgia, Athens, GA, 30602, USA
| | - Earle R Adams
- Department of Chemistry, University of Georgia, Athens, GA, 30602, USA
| | - Lirong Chen
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA
| | - John P Rose
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA
| | - Bi-Cheng Wang
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA
| | - Zheng-Hua Ye
- Department of Plant Biology, University of Georgia, Athens, GA, 30602, USA.
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2
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Zhong R, Phillips DR, Clark KD, Adams ER, Lee C, Ye ZH. Biochemical characterization of rice xylan biosynthetic enzymes in determining xylan chain elongation and substitutions. Plant Cell Physiol 2024:pcae028. [PMID: 38501734 DOI: 10.1093/pcp/pcae028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Revised: 03/05/2024] [Accepted: 03/18/2024] [Indexed: 03/20/2024]
Abstract
Grass xylan consists of a linear chain of β-1,4-linked xylosyl residues that often form domains substituted only with either arabinofuranose (Araf) or (methyl)glucuronic acid [(Me)GlcA] residues and it lacks the unique reducing end tetrasaccharide sequence found in dicot xylan. The mechanism of how grass xylan backbone elongation is initiated and how its distinctive substitution pattern is determined remain elusive. Here, we performed biochemical characterization of rice xylan biosynthetic enzymes, including xylan synthases, glucuronyltransferases and methyltransferases. Activity assays of rice xylan synthases demonstrated that they required short xylooligomers as acceptors for their activities. While rice xylan glucuronyltransferases effectively glucuronidated unsubstituted xylohexaose acceptors, they transferred little GlcA residues onto Araf-substituted xylohexaoses and rice xylan 3-O-arabinosyltransferase could not arabinosylate GlcA-substituted xylohexaoses, indicating that their intrinsic biochemical properties may contribute to the distinctive substitution pattern of rice xylan. In addition, we found that rice xylan methyltransferase exhibited a low substrate binding affinity, which may explain the partial GlcA methylation in rice xylan. Furthermore, immunolocalization of xylan in xylem cells of both rice and Arabidopsis showed that it was deposited together with cellulose in secondary walls without forming xylan-rich nanodomains. Together, our findings provide new insights into the biochemical mechanisms underlying xylan backbone elongation and substitutions in grass species.
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Affiliation(s)
- Ruiqin Zhong
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
| | - Dennis R Phillips
- Department of Chemistry, University of Georgia, Athens, GA 30602, USA
| | - Kevin D Clark
- Department of Chemistry, University of Georgia, Athens, GA 30602, USA
| | - Earle R Adams
- Department of Chemistry, University of Georgia, Athens, GA 30602, USA
| | - Chanhui Lee
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
- Department of Plant & Environmental New Resources, College of Life Sciences, Kyung Hee University, Yongin 17104, Republic of Korea
| | - Zheng-Hua Ye
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
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3
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Dickeson SK, Kumar S, Sun MF, Litvak M, He TZ, Phillips DR, Roberts ET, Feener EP, Law RHP, Gailani D. A mechanism for hereditary angioedema caused by a methionine-379-to-lysine substitution in kininogens. Blood 2024; 143:641-650. [PMID: 37992228 PMCID: PMC10873535 DOI: 10.1182/blood.2023022254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Revised: 10/20/2023] [Accepted: 11/13/2023] [Indexed: 11/24/2023] Open
Abstract
ABSTRACT Hereditary angioedema (HAE) is associated with episodic kinin-induced swelling of the skin and mucosal membranes. Most patients with HAE have low plasma C1-inhibitor activity, leading to increased generation of the protease plasma kallikrein (PKa) and excessive release of the nanopeptide bradykinin from high-molecular-weight kininogen (HK). However, disease-causing mutations in at least 10% of patients with HAE appear to involve genes for proteins other than C1-inhibitor. A point mutation in the Kng1 gene encoding HK and low-molecular weight kininogen (LK) was identified recently in a family with HAE. The mutation changes a methionine (Met379) to lysine (Lys379) in both proteins. Met379 is adjacent to the Lys380-Arg381 cleavage site at the N-terminus of the bradykinin peptide. Recombinant wild-type (Met379) and variant (Lys379) versions of HK and LK were expressed in HEK293 cells. PKa-catalyzed kinin release from HK and LK was not affected by the Lys379 substitutions. However, kinin release from HK-Lys379 and LK-Lys379 catalyzed by the fibrinolytic protease plasmin was substantially greater than from wild-type HK-Met379 and LK-Met379. Increased kinin release was evident when fibrinolysis was induced in plasma containing HK-Lys379 or LK-Lys379 compared with plasma containing wild-type HK or LK. Mass spectrometry revealed that the kinin released from wild-type and variant kininogens by PKa is bradykinin. Plasmin also released bradykinin from wild-type kininogens but cleaved HK-Lys379 and LK-Lys379 after Lys379 rather than Lys380, releasing the decapeptide Lys-bradykinin (kallidin). The Met379Lys substitutions make HK and LK better plasmin substrates, reinforcing the relationship between fibrinolysis and kinin generation.
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Affiliation(s)
- S. Kent Dickeson
- Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, TN
| | - Sunil Kumar
- Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, TN
| | - Mao-fu Sun
- Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, TN
| | - Maxim Litvak
- Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, TN
| | - Tracey Z. He
- Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, TN
| | | | | | | | - Ruby H. P. Law
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC, Australia
| | - David Gailani
- Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, TN
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Zhong R, Phillips DR, Adams ER, Ye ZH. An Arabidopsis family GT106 glycosyltransferase is essential for xylan biosynthesis and secondary wall deposition. Planta 2023; 257:43. [PMID: 36689015 DOI: 10.1007/s00425-023-04077-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Accepted: 01/14/2023] [Indexed: 06/17/2023]
Abstract
We have demonstrated that the Arabidopsis FRA9 (fragile fiber 9) gene is specifically expressed in secondary wall-forming cells and essential for the synthesis of the unique xylan reducing end sequence. Xylan is made of a linear chain of β-1,4-linked xylosyl (Xyl) residues that are often substituted with (methyl)glucuronic acid [(Me)GlcA] side chains and may be acetylated at O-2 and/or O-3. The reducing end of xylan from gymnosperms and dicots contains a unique tetrasaccharide sequence consisting of β-D-Xylp-(1 → 3)-α-L-Rhap-(1 → 2)-α-D-GalpA-(1 → 4)-D-Xylp, the synthesis of which requires four different glycosyltransferase activities. Genetic analysis in Arabidopsis thaliana has so far implicated three glycosyltransferase genes, FRA8 (fragile fiber 8), IRX8 (irregular xylem 8) and PARVUS, in the synthesis of this unique xylan reducing end sequence. Here, we report the essential role of FRA9, a member of glycosyltransferase family 106 (GT106), in the synthesis of this sequence. The expression of the FRA9 gene was shown to be induced by secondary wall master transcriptional regulators and specifically associated with secondary wall-forming cells, including xylem and fiber cells. T-DNA knockout mutation of the FRA9 gene caused impaired secondary cell wall thickening in leaf veins and a severe arrest of plant growth. RNA interference (RNAi) downregulation of FRA9 led to a significant reduction in secondary wall thickening of fibers, a deformation of xylem vessels and a decrease in xylan content. Structural analysis of xylanase-released xylooligomers revealed that RNAi downregulation of FRA9 resulted in a diminishment of the unique xylan reducing end sequence and complete methylation of xylan GlcA side chains, chemotypes reminiscent of those of the fra8, irx8 and parvus mutants. Furthermore, two FRA9 close homologs from Populus trichocarpa were found to be wood-associated functional orthologs of FRA9. Together, our findings uncover a member of the GT106 family as a new player involved in the synthesis of the unique reducing end sequence of xylan.
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Affiliation(s)
- Ruiqin Zhong
- Department of Plant Biology, University of Georgia, Athens, GA, 30602, USA
| | - Dennis R Phillips
- Department of Chemistry, University of Georgia, Athens, GA, 30602, USA
| | - Earle R Adams
- Department of Chemistry, University of Georgia, Athens, GA, 30602, USA
| | - Zheng-Hua Ye
- Department of Plant Biology, University of Georgia, Athens, GA, 30602, USA.
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5
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Zhong R, Lee C, Cui D, Phillips DR, Adams ER, Jeong HY, Jung KH, Ye ZH. Identification of xylan arabinosyl 2-O-xylosyltransferases catalyzing the addition of 2-O-xylosyl residue onto arabinosyl side chains of xylan in grass species. Plant J 2022; 112:193-206. [PMID: 35959609 DOI: 10.1111/tpj.15939] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 07/13/2022] [Accepted: 08/09/2022] [Indexed: 06/15/2023]
Abstract
Grass xylan, the major hemicellulose in both primary and secondary cell walls, is heavily decorated with α-1,3-linked arabinofuranosyl (Araf) residues that may be further substituted at O-2 with xylosyl (Xyl) or Araf residues. Although xylan 3-O-arabinosyltransferases (XATs) catalyzing 3-O-Araf addition onto xylan have been characterized, glycosyltransferases responsible for the transfer of 2-O-Xyl or 2-O-Araf onto 3-O-Araf residues of xylan to produce the Xyl-Araf and Araf-Araf disaccharide side chains remain to be identified. In this report, we showed that a rice GT61 member, named OsXAXT1 (xylan arabinosyl 2-O-xylosyltransferase 1) herein, was able to mediate the addition of Xyl-Araf disaccharide side chains onto xylan when heterologously co-expressed with OsXAT2 in the Arabidopsis gux1/2/3 (glucuronic acid substitution of xylan 1/2/3) triple mutant that lacks any glycosyl substitutions. Recombinant OsXAXT1 protein expressed in human embryonic kidney 293 cells exhibited a xylosyltransferase activity catalyzing the addition of Xyl from UDP-Xyl onto arabinosylated xylooligomers. Consistent with its function as a xylan arabinosyl 2-O-xylosyltransferase, CRISPR-Cas9-mediated mutations of the OsXAXT1 gene in transgenic rice plants resulted in a reduction in the level of Xyl-Araf disaccharide side chains in xylan. Furthermore, we revealed that XAXT1 close homologs from several other grass species, including switchgrass, maize, and Brachypodium, possessed the same functions as OsXAXT1, indicating functional conservation of XAXTs in grass species. Together, our findings establish that grass XAXTs are xylosyltransferases catalyzing Xyl transfer onto O-2 of Araf residues of xylan to form the Xyl-Araf disaccharide side chains, which furthers our understanding of genes involved in xylan biosynthesis.
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Affiliation(s)
- Ruiqin Zhong
- Department of Plant Biology, University of Georgia, Athens, GA, 30602, USA
| | - Chanhui Lee
- Department of Plant & Environmental New Resources, College of Life Sciences, Kyung Hee University, Yongin, 17104, Republic of Korea
| | - Dongtao Cui
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, 02138, USA
| | - Dennis R Phillips
- Department of Chemistry, University of Georgia, Athens, GA, 30602, USA
| | - Earle R Adams
- Department of Chemistry, University of Georgia, Athens, GA, 30602, USA
| | - Ho-Young Jeong
- Department of Plant & Environmental New Resources, College of Life Sciences, Kyung Hee University, Yongin, 17104, Republic of Korea
| | - Ki-Hong Jung
- Graduate School of Green-Bio Science, Kyung Hee University, Yongin, 17104, Republic of Korea
| | - Zheng-Hua Ye
- Department of Plant Biology, University of Georgia, Athens, GA, 30602, USA
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6
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Zhong R, Phillips DR, Ye ZH. Independent recruitment of glycosyltransferase family 61 members for xylan substitutions in conifers. Planta 2022; 256:70. [PMID: 36068444 DOI: 10.1007/s00425-022-03989-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Accepted: 08/31/2022] [Indexed: 06/15/2023]
Abstract
Several pine members of the gymnosperm-specific GT61 clades were demonstrated to be arabinosyltransferases and xylosyltransferases catalyzing the transfer of 2-O-Araf, 3-O-Araf and 2-O-Xyl side chains onto xylooligomer acceptors, indicating their possible involvement in Araf and Xyl substitutions of xylan in pine. Xylan in conifer wood is substituted at O-2 with methylglucuronic acid (MeGlcA) as well as at O-3 with arabinofuranose (Araf), which differs from xylan in dicot wood that is typically decorated with MeGlcA but not Araf. Currently, glycosyltransferases responsible for conifer xylan arabinosylation have not been identified. Here, we investigated the roles of pine glycosyltransferase family 61 (GT61) members in xylan substitutions. Biochemical characterization of four pine wood-associated GT61 members showed that they exhibited three distinct glycosyltransferase activities involved in xylan substitutions. Two of them catalyzed the addition of 2-O-α-Araf or 3-O-α-Araf side chains onto xylooligomer acceptors and thus were named Pinus taeda xylan 2-O-arabinosyltransferase 1 (PtX2AT1) and 3-O-arabinosyltransferase 1 (PtX3AT1), respectively. Two other pine GT61 members were found to be xylan 2-O-xylosyltransferases (PtXYXTs) adding 2-O-β-Xyl side chains onto xylooligomer acceptors. Furthermore, sequential reactions with PtX3AT1 and the PtGUX1 xylan glucuronyltransferase demonstrated that PtX3AT1 could efficiently arabinosylate glucuronic acid (GlcA)-substituted xylooligomers and likewise, PtGUX1 was able to add GlcA side chains onto 3-O-Araf-substituted xylooligomers. Phylogenetic analysis revealed that PtX2AT1, PtX3AT1 and PtXYXTs resided in three gymnosperm-specific GT61 clades that are separated from the grass-expanded GT61 clade harboring xylan 3-O-arabinosyltransferases and 2-O-xylosyltransferases, suggesting that they might have been recruited independently for xylan substitutions in gymnosperms. Together, our findings have established several pine GT61 members as xylan 2-O- and 3-O-arabinosyltransferases and 2-O-xylosyltransferases and they indicate that pine xylan might also be substituted with 2-O-Araf and 2-O-Xyl side chains.
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Affiliation(s)
- Ruiqin Zhong
- Department of Plant Biology, University of Georgia, Athens, GA, 30602, USA
| | - Dennis R Phillips
- Department of Chemistry, University of Georgia, Athens, GA, 30602, USA
| | - Zheng-Hua Ye
- Department of Plant Biology, University of Georgia, Athens, GA, 30602, USA.
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7
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Dickeson SK, Kumar S, Sun MF, Mohammed BM, Phillips DR, Whisstock JC, Quek AJ, Feener EP, Law RHP, Gailani D. A mechanism for hereditary angioedema caused by a lysine 311-to-glutamic acid substitution in plasminogen. Blood 2022; 139:2816-2829. [PMID: 35100351 PMCID: PMC9074402 DOI: 10.1182/blood.2021012945] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 01/18/2022] [Indexed: 11/20/2022] Open
Abstract
Patients with hereditary angioedema (HAE) experience episodes of bradykinin (BK)-induced swelling of skin and mucosal membranes. The most common cause is reduced plasma activity of C1 inhibitor, the main regulator of the proteases plasma kallikrein (PKa) and factor XIIa (FXIIa). Recently, patients with HAE were described with a Lys311 to glutamic acid substitution in plasminogen (Plg), the zymogen of the protease plasmin (Plm). Adding tissue plasminogen activator to plasma containing Plg-Glu311 vs plasma containing wild-type Plg (Plg-Lys311) results in greater BK generation. Similar results were obtained in plasma lacking prekallikrein or FXII (the zymogens of PKa and FXIIa) and in normal plasma treated with a PKa inhibitor, indicating Plg-Glu311 induces BK generation independently of PKa and FXIIa. Plm-Glu311 cleaves high and low molecular weight kininogens (HK and LK, respectively), releasing BK more efficiently than Plm-Lys311. Based on the plasma concentrations of HK and LK, the latter may be the source of most of the BK generated by Plm-Glu311. The lysine analog ε-aminocaproic acid blocks Plm-catalyzed BK generation. The Glu311 substitution introduces a lysine-binding site into the Plg kringle 3 domain, perhaps altering binding to kininogens. Plg residue 311 is glutamic acid in most mammals. Glu311 in patients with HAE, therefore, represents reversion to the ancestral condition. Substantial BK generation occurs during Plm-Glu311 cleavage of human HK, but not mouse HK. Furthermore, mouse Plm, which has Glu311, did not liberate BK from human kininogens more rapidly than human Plg-Lys311. This indicates Glu311 is pathogenic in the context of human Plm when human kininogens are the substrates.
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Affiliation(s)
- S Kent Dickeson
- Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, TN
| | - Sunil Kumar
- Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, TN
| | - Mao-Fu Sun
- Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, TN
| | - Bassem M Mohammed
- Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, TN
| | | | - James C Whisstock
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC, Australia; and
| | - Adam J Quek
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC, Australia; and
| | | | - Ruby H P Law
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC, Australia; and
| | - David Gailani
- Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, TN
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8
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Zhong R, Phillips DR, Ye ZH. A Single Xyloglucan Xylosyltransferase Is Sufficient for Generation of the XXXG Xylosylation Pattern of Xyloglucan. Plant Cell Physiol 2021; 62:1589-1602. [PMID: 34264339 DOI: 10.1093/pcp/pcab113] [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] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 07/13/2021] [Accepted: 07/14/2021] [Indexed: 05/26/2023]
Abstract
Xyloglucan is the most abundant hemicellulose in the primary cell walls of dicots. Dicot xyloglucan is the XXXG type consisting of repeating units of three consecutive xylosylated Glc residues followed by one unsubstituted Glc. Its xylosylation is catalyzed by xyloglucan 6-xylosyltransferases (XXTs) and there exist five XXTs (AtXXT1-5) in Arabidopsis. While AtXXT1 and AtXXT2 have been shown to add the first two Xyl residues in the XXXG repeat, which XXTs are responsible for the addition of the third Xyl residue remains elusive although AtXXT5 was a proposed candidate. In this report, we generated recombinant proteins of all five Arabidopsis XXTs and one rice XXT (OsXXT1) in the mammalian HEK293 cells and investigated their ability to sequentially xylosylate Glc residues to generate the XXXG xylosylation pattern. We found that like AtXXT1/2, AtXXT4 and OsXXT1 could efficiently xylosylate the cellohexaose (G6) acceptor to produce mono- and di-xylosylated G6, whereas AtXXT5 was only barely capable of adding one Xyl onto G6. When AtXXT1-catalyzed products were used as acceptors, AtXXT1/2/4 and OsXXT1, but not AtXXT5, were able to xylosylate additional Glc residues to generate tri- and tetra-xylosylated G6. Further characterization of the tri- and tetra-xylosylated G6 revealed that they had the sequence of GXXXGG and GXXXXG with three and four consecutive xylosylated Glc residues, respectively. In addition, we have found that although tri-xylosylation occurred on G6, cello-oligomers with a degree of polymerization of 3 to 5 could only be mono- and di-xylosylated. Together, these results indicate that each of AtXXT1/2/4 and OsXXT1 is capable of sequentially adding Xyl onto three contiguous Glc residues to generate the XXXG xylosylation pattern and these findings provide new insight into the biochemical mechanism underlying xyloglucan biosynthesis.
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Affiliation(s)
- Ruiqin Zhong
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
| | - Dennis R Phillips
- Department of Chemistry, University of Georgia, Athens, GA 30602, USA
| | - Zheng-Hua Ye
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
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9
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Zhong R, Cui D, Phillips DR, Sims NT, Ye ZH. Functional analysis of GT61 glycosyltransferases from grass species in xylan substitutions. Planta 2021; 254:131. [PMID: 34821996 DOI: 10.1007/s00425-021-03794-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 11/16/2021] [Indexed: 06/13/2023]
Abstract
Multiple rice GT61 members were demonstrated to be xylan arabinosyltransferases (XATs) mediating 3-O-arabinosylation of xylan and the functions of XATs and xylan 2-O-xylosyltransferases were shown to be conserved in grass species. Xylan is the major hemicellulose in the cell walls of grass species and it is typified by having arabinofuranosyl (Araf) substitutions. In this report, we demonstrated that four previously uncharacterized, Golgi-localized glycosyltransferases residing in clade A or B of the rice GT61 family were able to mediate 3-O-arabinosylation of xylan when heterologously expressed in the Arabidopsis gux1/2/3 triple mutant. Biochemical characterization of their recombinant proteins established that they were xylan arabinosyltransferases (XATs) capable of transferring Araf residues onto xylohexaose acceptors, and thus they were named OsXAT4, OsXAT5, OsXAT6 and OsXAT7. OsXAT5 and the previously identified OsXAT2 were shown to be able to arabinosylate xylooligomers with a degree of polymerization of as low as 3. Furthermore, a number of XAT homologs from maize, sorghum, Brachypodium and switchgrass were found to exhibit activities catalyzing Araf transfer onto xylohexaose, indicating that they are XATs involved in xylan arabinosylation in these grass species. Moreover, we revealed that homologs of another GT61 member, xylan 2-O-xylosyltransferase (XYXT1), from these grass species could mediate 2-O-xylosylation of xylan when expressed in the Arabidopsis gux1/2/3 mutant. Together, our findings indicate that multiple OsXATs are involved in 3-O-arabinosylation of xylan and the functions of XATs and XYXTs are conserved in grass species.
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Affiliation(s)
- Ruiqin Zhong
- Department of Plant Biology, University of Georgia, Athens, GA, 30602, USA
| | - Dongtao Cui
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, 02138, USA
| | - Dennis R Phillips
- Department of Chemistry, University of Georgia, Athens, GA, 30602, USA
| | - Nathanael T Sims
- Department of Plant Biology, University of Georgia, Athens, GA, 30602, USA
| | - Zheng-Hua Ye
- Department of Plant Biology, University of Georgia, Athens, GA, 30602, USA.
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10
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Drischler C, Furnstahl RJ, Melendez JA, Phillips DR. How Well Do We Know the Neutron-Matter Equation of State at the Densities Inside Neutron Stars? A Bayesian Approach with Correlated Uncertainties. Phys Rev Lett 2020; 125:202702. [PMID: 33258658 DOI: 10.1103/physrevlett.125.202702] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Revised: 07/28/2020] [Accepted: 09/25/2020] [Indexed: 06/12/2023]
Abstract
We introduce a new framework for quantifying correlated uncertainties of the infinite-matter equation of state derived from chiral effective field theory (χEFT). Bayesian machine learning via Gaussian processes with physics-based hyperparameters allows us to efficiently quantify and propagate theoretical uncertainties of the equation of state, such as χEFT truncation errors, to derived quantities. We apply this framework to state-of-the-art many-body perturbation theory calculations with nucleon-nucleon and three-nucleon interactions up to fourth order in the χEFT expansion. This produces the first statistically robust uncertainty estimates for key quantities of neutron stars. We give results up to twice nuclear saturation density for the energy per particle, pressure, and speed of sound of neutron matter, as well as for the nuclear symmetry energy and its derivative. At nuclear saturation density, the predicted symmetry energy and its slope are consistent with experimental constraints.
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Affiliation(s)
- C Drischler
- Department of Physics, University of California, Berkeley, California 94720, USA
- Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - R J Furnstahl
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - J A Melendez
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - D R Phillips
- Department of Physics and Astronomy and Institute of Nuclear and Particle Physics, Ohio University, Athens, Ohio 45701, USA
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11
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Zhong R, Cui D, Phillips DR, Richardson EA, Ye ZH. A Group of O-Acetyltransferases Catalyze Xyloglucan Backbone Acetylation and Can Alter Xyloglucan Xylosylation Pattern and Plant Growth When Expressed in Arabidopsis. Plant Cell Physiol 2020; 61:1064-1079. [PMID: 32167545 PMCID: PMC7295396 DOI: 10.1093/pcp/pcaa031] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 03/08/2020] [Indexed: 05/23/2023]
Abstract
Xyloglucan is a major hemicellulose in plant cell walls and exists in two distinct types, XXXG and XXGG. While the XXXG-type xyloglucan from dicot species only contains O-acetyl groups on side-chain galactose (Gal) residues, the XXGG-type xyloglucan from Poaceae (grasses) and Solanaceae bears O-acetyl groups on backbone glucosyl (Glc) residues. Although O-acetyltransferases responsible for xyloglucan Gal acetylation have been characterized, the biochemical mechanism underlying xyloglucan backbone acetylation remains to be elucidated. In this study, we showed that recombinant proteins of a group of DUF231 members from rice and tomato were capable of transferring acetyl groups onto O-6 of Glc residues in cello-oligomer acceptors, indicating that they are xyloglucan backbone 6-O-acetyltransferases (XyBATs). We further demonstrated that XyBAT-acetylated cellohexaose oligomers could be readily xylosylated by AtXXT1 (Arabidopsis xyloglucan xylosyltransferase 1) to generate acetylated, xylosylated cello-oligomers, whereas AtXXT1-xylosylated cellohexaose oligomers were much less effectively acetylated by XyBATs. Heterologous expression of a rice XyBAT in Arabidopsis led to a severe reduction in cell expansion and plant growth and a drastic alteration in xyloglucan xylosylation pattern with the formation of acetylated XXGG-type units, including XGG, XGGG, XXGG, XXGG,XXGGG and XXGGG (G denotes acetylated Glc). In addition, recombinant proteins of two Arabidopsis XyBAT homologs also exhibited O-acetyltransferase activity toward cellohexaose, suggesting their possible role in mediating xyloglucan backbone acetylation in vivo. Our findings provide new insights into the biochemical mechanism underlying xyloglucan backbone acetylation and indicate the importance of maintaining the regular xyloglucan xylosylation pattern in cell wall function.
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Affiliation(s)
- Ruiqin Zhong
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
| | - Dongtao Cui
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA
| | - Dennis R Phillips
- Department of Chemistry, University of Georgia, Athens, GA 30602, USA
| | | | - Zheng-Hua Ye
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
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12
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Zhong R, Cui D, Richardson EA, Phillips DR, Azadi P, Lu G, Ye ZH. Cytosolic Acetyl-CoA Generated by ATP-Citrate Lyase Is Essential for Acetylation of Cell Wall Polysaccharides. Plant Cell Physiol 2020; 61:64-75. [PMID: 31503286 DOI: 10.1093/pcp/pcz178] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 09/04/2019] [Indexed: 05/12/2023]
Abstract
Plant cell wall polysaccharides, including xylan, glucomannan, xyloglucan and pectin, are often acetylated. Although a number of acetyltransferases responsible for the acetylation of some of these polysaccharides have been biochemically characterized, little is known about the source of acetyl donors and how acetyl donors are translocated into the Golgi, where these polysaccharides are synthesized. In this report, we investigated roles of ATP-citrate lyase (ACL) that generates cytosolic acetyl-CoA in cell wall polysaccharide acetylation and effects of simultaneous mutations of four Reduced Wall Acetylation (RWA) genes on acetyl-CoA transport into the Golgi in Arabidopsis thaliana. Expression analyses of genes involved in the generation of acetyl-CoA in different subcellular compartments showed that the expression of several ACL genes responsible for cytosolic acetyl-CoA synthesis was elevated in interfascicular fiber cells and induced by secondary wall-associated transcriptional activators. Simultaneous downregulation of the expression of ACL genes was demonstrated to result in a substantial decrease in the degree of xylan acetylation and a severe alteration in secondary wall structure in xylem vessels. In addition, the degree of acetylation of other cell wall polysaccharides, including glucomannan, xyloglucan and pectin, was also reduced. Moreover, Golgi-enriched membrane vesicles isolated from the rwa1/2/3/4 quadruple mutant were found to exhibit a drastic reduction in acetyl-CoA transport activity compared with the wild type. These findings indicate that cytosolic acetyl-CoA generated by ACL is essential for cell wall polysaccharide acetylation and RWAs are required for its transport from the cytosol into the Golgi.
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Affiliation(s)
- Ruiqin Zhong
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
| | - Dongtao Cui
- Department of Chemistry, University of Georgia, Athens, GA 30602, USA
| | | | - Dennis R Phillips
- Department of Chemistry, University of Georgia, Athens, GA 30602, USA
| | - Parastoo Azadi
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602, USA
| | - Grace Lu
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602, USA
| | - Zheng-Hua Ye
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
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13
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Zhong R, Cui D, Phillips DR, Ye ZH. A Novel Rice Xylosyltransferase Catalyzes the Addition of 2-O-Xylosyl Side Chains onto the Xylan Backbone. Plant Cell Physiol 2018; 59:554-565. [PMID: 29325159 DOI: 10.1093/pcp/pcy003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2017] [Accepted: 01/03/2018] [Indexed: 05/02/2023]
Abstract
Xylan is a major hemicellulose in both primary and secondary walls of grass species. It consists of a linear backbone of β-1,4-linked xylosyl residues that are often substituted with monosaccharides and disaccharides. Xylosyl substitutions directly on the xylan backbone have not been reported in grass species, and genes responsible for xylan substitutions in grass species have not been well elucidated. Here, we report functional characterization of a rice (Oryza sativa) GT61 glycosyltransferase, XYXT1 (xylan xylosyltransferase1), for its role in xylan substitutions. XYXT1 was found to be ubiquitously expressed in different rice organs and its encoded protein was targeted to the Golgi, the site for xylan biosynthesis. When expressed in the Arabidopsis gux1/2/3 triple mutant, in which xylan was completely devoid of sugar substitutions, XYXT1 was able to add xylosyl side chains onto xylan. Glycosyl linkage analysis and comprehensive structural characterization of xylooligomers generated by xylanase digestion of xylan from transgenic Arabidopsis plants expressing XYXT1 revealed that the side chain xylosyl residues were directly attached to the xylan backbone at O-2, a substituent not present in wild-type Arabidopsis xylan. XYXT1 was unable to add xylosyl residues onto the arabinosyl side chains of xylan when it was co-expressed with OsXAT2 (Oryza sativa xylan arabinosyltransferase2) in the gux1/2/3 triple mutant. Furthermore, we showed that recombinant XYXT1 possessed an activity transferring xylosyl side chains onto xylooligomer acceptors, whereas recombinant OsXAT2 catalyzed the addition of arabinosyl side chains onto xylooligomer acceptors. Our findings from both an in vivo gain-of-function study and an in vitro recombinant protein activity assay demonstrate that XYXT1 is a novel β-1,2-xylosyltransferase mediating the addition of xylosyl side chains onto xylan.
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Affiliation(s)
- Ruiqin Zhong
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
| | - Dongtao Cui
- Department of Chemistry, University of Georgia, Athens, GA 30602, USA
| | - Dennis R Phillips
- Department of Chemistry, University of Georgia, Athens, GA 30602, USA
| | - Zheng-Hua Ye
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
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14
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Abstract
The development since the late 1970s of four Special Economic Zones in South China, in which a variety of economic change is being piloted, has now been widely documented. These zones have certain similarities with Export Processing Zones in some other countries within Southeast Asia, although they are more comprehensive in development and include the provision of housing for foreigners and local Chinese, as well as social services and many other facilities. Housing and service provision has, to an extent, however, lagged behind the economic and physical development of the Chinese zones. The authorities in the zones have begun to view housing as an item worthy of investment, and the coexistence of foreign firms and joint ventures with Chinese-owned undertakings within the zones has meant that incomes and aspirations, and hence demands for facilities, are often higher than elsewhere in the country. This has meant an important re-examination of socialist principles in the zones. Housing in particular is becoming a commodity which is of higher quality than elsewhere in China and can be bought and sold, and many types of social and retail services are also being provided by individuals and firms rather than by the state or larger production units. In this paper the authors examine some of the changes currently being witnessed in these zones and the dilemmas which they pose for a government still attempting to maintain an avowed socialist orientation in its policy. In particular, they discuss the emergence of competition for housing and resources, and consider the extent to which the commodification of social facilities is compatible with the continuation of socialist state policy.
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Affiliation(s)
- D R Phillips
- Department of Geography, University of Exeter, Exeter EX4 4RJ, England
| | - A G O Yeh
- Centre of Urban Studies and Urban Planning, University of Hong Kong, Hong Kong
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15
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Valderrama MP, Phillips DR. Power counting of contact-range currents in effective field theory. Phys Rev Lett 2015; 114:082502. [PMID: 25768760 DOI: 10.1103/physrevlett.114.082502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2014] [Indexed: 06/04/2023]
Abstract
We analyze the power counting of two-body currents in nuclear effective field theories (EFTs). We find that the existence of nonperturbative physics at low energies, which is manifest in the existence of the deuteron and the ^{1}S_{0} NN virtual bound state, combined with the appearance of singular potentials in versions of nuclear EFT that incorporate chiral symmetry, modifies the renormalization-group flow of the couplings associated with contact operators that involve nucleon-nucleon pairs and external fields. The order of these couplings is thereby enhanced with respect to the naive-dimensional-analysis estimate. Consequently, short-range currents enter at a lower order in the chiral EFT than has been appreciated up until now, and their impact on low-energy observables is concomitantly larger. We illustrate the changes in the power counting with a few low-energy processes involving external probes and few-nucleon systems, including electron-deuteron elastic scattering and radiative neutron capture by protons.
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Affiliation(s)
- M Pavón Valderrama
- Institut de Physique Nucléaire, Université Paris-Sud, IN2P3/CNRS, F-91406 Orsay Cedex, France
| | - D R Phillips
- Institute of Nuclear and Particle Physics and Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701, USA
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16
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Myers LS, Annand JRM, Brudvik J, Feldman G, Fissum KG, Grießhammer HW, Hansen K, Henshaw SS, Isaksson L, Jebali R, Kovash MA, Lundin M, McGovern JA, Middleton DG, Nathan AM, Phillips DR, Schröder B, Stave SC. Measurement of Compton scattering from the deuteron and an improved extraction of the neutron electromagnetic polarizabilities. Phys Rev Lett 2014; 113:262506. [PMID: 25615318 DOI: 10.1103/physrevlett.113.262506] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Indexed: 06/04/2023]
Abstract
The electromagnetic polarizabilities of the nucleon are fundamental properties that describe its response to external electric and magnetic fields. They can be extracted from Compton-scattering data-and have been, with good accuracy, in the case of the proton. In contradistinction, information for the neutron requires the use of Compton scattering from nuclear targets. Here, we report a new measurement of elastic photon scattering from deuterium using quasimonoenergetic tagged photons at the MAX IV Laboratory in Lund, Sweden. These first new data in more than a decade effectively double the world data set. Their energy range overlaps with previous experiments and extends it by 20 MeV to higher energies. An analysis using chiral effective field theory with dynamical Δ(1232) degrees of freedom shows the data are consistent with and within the world data set. After demonstrating that the fit is consistent with the Baldin sum rule, extracting values for the isoscalar nucleon polarizabilities, and combining them with a recent result for the proton, we obtain the neutron polarizabilities as αn=[11.55±1.25(stat)±0.2(BSR)±0.8(th)]×10(-4) fm(3) and βn=[3.65∓1.25(stat)±0.2(BSR)∓0.8(th)]×10(-4) fm(3), with χ(2)=45.2 for 44 degrees of freedom.
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Affiliation(s)
- L S Myers
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - J R M Annand
- School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom
| | - J Brudvik
- MAX IV Laboratory, Lund University, SE-221 00 Lund, Sweden
| | - G Feldman
- Institute for Nuclear Studies, Department of Physics, The George Washington University, Washington, DC 20052, USA
| | - K G Fissum
- Department of Physics, Lund University, SE-221 00 Lund, Sweden
| | - H W Grießhammer
- Institute for Nuclear Studies, Department of Physics, The George Washington University, Washington, DC 20052, USA
| | - K Hansen
- MAX IV Laboratory, Lund University, SE-221 00 Lund, Sweden
| | - S S Henshaw
- Department of Physics, Duke University, Durham, North Carolina 27708, USA
| | - L Isaksson
- MAX IV Laboratory, Lund University, SE-221 00 Lund, Sweden
| | - R Jebali
- School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom
| | - M A Kovash
- Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506, USA
| | - M Lundin
- MAX IV Laboratory, Lund University, SE-221 00 Lund, Sweden
| | - J A McGovern
- School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, United Kingdom
| | - D G Middleton
- Kepler Centre for Astro- and Particle Physics, Physikalisches Institut, Universität Tübingen, D-72076 Tübingen, Germany
| | - A M Nathan
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - D R Phillips
- Department of Physics and Astronomy and Institute of Nuclear and Particle Physics, Ohio University, Athens, Ohio 45701, USA
| | - B Schröder
- MAX IV Laboratory, Lund University, SE-221 00 Lund, Sweden and Department of Physics, Lund University, SE-221 00 Lund, Sweden
| | - S C Stave
- Department of Physics, Duke University, Durham, North Carolina 27708, USA
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17
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Phillips DR. Radiometals development in the U.S. Department of Energy Isotope Program. Nucl Med Biol 2014. [DOI: 10.1016/j.nucmedbio.2014.05.131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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18
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Flores FP, Singh RK, Kerr WL, Phillips DR, Kong F. In vitro release properties of encapsulated blueberry (Vaccinium ashei) extracts. Food Chem 2014; 168:225-32. [PMID: 25172704 DOI: 10.1016/j.foodchem.2014.07.059] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [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: 03/25/2014] [Revised: 06/16/2014] [Accepted: 07/07/2014] [Indexed: 02/06/2023]
Abstract
We aimed to determine the effect of encapsulation on the release properties of blueberry extracts during simulated gastrointestinal digestion. An ethanolic pomace extract was microencapsulated with whey protein isolate via spray drying. The in vitro release of monomeric anthocyanins, phenolics and ferric reducing antioxidant activity of the microcapsules (W) were evaluated for the microcapsules and two non-encapsulated systems: ethanolic pomace extract (P) and freeze-dried juice (F). Concentrations of anthocyanin and phenolics were normalised prior to digestion. Results showed that antioxidant activity was in the order of: F>W>P. Regardless of encapsulation, more phenolics were released from W and P than F. Anthocyanin concentration decreased after intestinal digestion for W, but remained constant for P and F. MALDI-MS showed similar spectra for P and F but not for W. The spray-dried product has comparable release characteristics to freeze-dried juice, and may be investigated for food applications.
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Affiliation(s)
- Floirendo P Flores
- Department of Food Science and Technology, The University of Georgia, 100 Cedar St., Athens, GA 30602-2610, USA; Institute of Food Science and Technology, University of the Philippines Los Baños, College, Laguna 4031, Philippines
| | - Rakesh K Singh
- Department of Food Science and Technology, The University of Georgia, 100 Cedar St., Athens, GA 30602-2610, USA
| | - William L Kerr
- Department of Food Science and Technology, The University of Georgia, 100 Cedar St., Athens, GA 30602-2610, USA
| | - Dennis R Phillips
- Proteomic and Mass Spectrometry (PAMS) Core Facility, Department of Chemistry, The University of Georgia, 140 Cedar St., Athens, GA 30602, USA
| | - Fanbin Kong
- Department of Food Science and Technology, The University of Georgia, 100 Cedar St., Athens, GA 30602-2610, USA.
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19
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Kim YK, Phillips DR, Tao Y. Evidence for no sexual isolation between Drosophila albomicans and D. nasuta. Ecol Evol 2013; 3:2061-74. [PMID: 23919152 PMCID: PMC3728947 DOI: 10.1002/ece3.619] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [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: 02/18/2013] [Revised: 04/22/2013] [Accepted: 05/01/2013] [Indexed: 11/26/2022] Open
Abstract
Sexual isolation, the reduced tendency to mate, is one of the reproductive barriers that prevent gene flow between different species. Various species-specific signals during courtship contribute to sexual isolation between species. Drosophila albomicans and D. nasuta are closely related species of the nasuta subgroup within the Drosophila immigrans group and are distributed in allopatry. We analyzed mating behavior and courtship as well as cuticular hydrocarbon profiles within and between species. Here, we report that these two species randomly mated with each other. We did not observe any sexual isolation between species or between strains within species by multiple-choice tests. Significant difference in the courtship index was detected between these two species, but males and females of both species showed no discrimination against heterospecific partners. Significant quantitative variations in cuticular hydrocarbons between these two species were also found, but the cuticular hydrocarbons appear to play a negligible role in both courtship and sexual isolation between these two species. In contrast to the evident postzygotic isolation, the lack of sexual isolation between these two species suggests that the evolution of premating isolation may lag behind that of the intergenomic incompatibility, which might be driven by intragenomic conflicts.
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Affiliation(s)
- Yong-Kyu Kim
- Department of Biology, Emory University Atlanta, Georgia, 30322 ; Howard Hughes Medical Institute, Janelia Farm Research Campus 19700 Helix Drive, Ashburn, Virginia, 20147
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20
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Barbour A, Elgalib A, Draper S, Phillips DR. P23 ‘This is a policy not a pilot’: how to implement routine opt-out HIV testing for acute medical admissions in an NHS trust in a high prevalence area. Br J Vener Dis 2012. [DOI: 10.1136/sextrans-2012-050601c.23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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21
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Bilardi RA, Kimura KI, Phillips DR, Cutts SM. Processing of anthracycline-DNA adducts via DNA replication and interstrand crosslink repair pathways. Biochem Pharmacol 2012; 83:1241-50. [PMID: 22326903 DOI: 10.1016/j.bcp.2012.01.029] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2011] [Revised: 01/25/2012] [Accepted: 01/26/2012] [Indexed: 11/24/2022]
Abstract
Anthracycline chemotherapeutics are well characterised as poisons of topoisomerase II, however many anthracyclines, including doxorubicin, are also capable of forming drug-DNA adducts. Anthracycline-DNA adducts present an unusual obstacle for cells as they are covalently attached to one DNA strand and stabilised by hydrogen bonding to the other strand. We now show that in cycling cells processing of anthracycline adducts through DNA replication appears dominant compared to processing via transcription-coupled pathways, and that the processing of these adducts into DNA breaks is independent of topoisomerase II. It has previously been shown that cells deficient in homologous recombination (HR) are hypersensitive to adduct forming treatments. Given that anthracycline-DNA adducts, whilst not true crosslinks, are associated with both DNA strands, the role of ICL repair pathways was investigated. Mus81 is a structure specific nuclease implicated in Holliday junction resolution and the resolution of branched DNA formed by stalled replication forks. We now show that ICL repair deficient cells (Mus81(-/-)) are hypersensitive to anthracycline-DNA adducts and ET-743, a compound which causes a chemically similar type of DNA damage. Further analysis of this mechanism showed that Mus81 does not appear to cause DNA breaks resulting from either anthracycline- or ET743-DNA adducts. This suggests Mus81 processes these novel forms of DNA damage in a fundamentally different way compared to the processing of classical covalent crosslinks. Improved understanding of the role of DNA repair in response to such adducts may lead to more effective chemotherapy for patients with BRCA1/2 mutations and other HR deficiencies.
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Affiliation(s)
- R A Bilardi
- Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Victoria 3086, Australia
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22
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Kim YK, Ruiz-García M, Alvarez D, Phillips DR, Anderson WW. Sexual isolation between North American and Bogota strains of Drosophila pseudoobscura. Behav Genet 2011; 42:472-82. [PMID: 22065259 DOI: 10.1007/s10519-011-9517-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2010] [Accepted: 10/19/2011] [Indexed: 11/30/2022]
Abstract
Sexual isolation, the reduced ability of organisms of different species to successfully mate, is one of the reproductive barriers that prevent gene flow between different taxa. Various species-specific signals during courtship are attributed to the sexual isolation between them. Drosophila pseudoobscura has been widely used to study the behavioral and genetic mechanisms underlying selection for sexual isolation, as a model system for speciation. D. pseudoobscura and its sibling species, D. persmilis, live together in many locations but are reproductively isolated from one another. North American geographic strains of D. pseudoobscura from the American West mate at random. Several decades ago, D. pseudoobscura was collected in the vicinity of Bogota, Colombia, and later named the subspecies D. pseudoobscura bogotana. Nearly 5,000 matings were observed in this study. We analyzed mating behavior and cuticular hydrocarbon profiles as well as courtship within and between North American and Bogota strains of D. pseudoobscura. Here we report for the first time that Bogota strains of D. pseudoobscura do show statistically significant sexual isolation from North American strains. In addition, there are quantitative variations in cuticular hydrocarbons as well as in courtship behavior between Bogota and North American strains, and females of both North American and Bogota strains show strong preference for North American strain males having high mating propensities, suggesting that the Bogota strains are at an early stage that could lead to a separate species.
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Affiliation(s)
- Yong-Kyu Kim
- Department of Biology, Emory University, Atlanta, GA 30322, USA.
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23
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Lu Y, Phillips DR, Lu L, Hardin IR. Determination of the degradation products of selected sulfonated phenylazonaphthol dyes treated by white rot fungus Pleurotus ostreatus by capillary electrophoresis coupled with electrospray ionization ion trap mass spectrometry. J Chromatogr A 2008; 1208:223-31. [PMID: 18778834 DOI: 10.1016/j.chroma.2008.08.080] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2007] [Revised: 08/13/2008] [Accepted: 08/15/2008] [Indexed: 10/21/2022]
Abstract
The removal of water-soluble sulphonated phenylazonaphthol dye effluents generated by textile industries is an important issue in wastewater treatment. Microbial treatment of environmental pollutants including dyes, with white rot fungi has received wide attention as a potential alternative for conventional methods in wastewater treatment. Three sulphonated phenylazonaphthol dyes with similar molecular structures Acid Orange 7, Acid Orange 8 and Mordant Violet 5 were selected and degraded by the white rot fungus Pleurotus ostreatus. Chemical instrumental analysis methods such as high-performance liquid chromatography (HPLC) and capillary electrophoresis combined with electrospray ionization mass spectrometry (CE-ESI-MS) were used to identify the degraded dyes. Mordant Violet 5 had two degradation pathways when degraded by P. ostreatus. The first degradation pathway for Mordant Violet 5 was for trans structure and the cis-Mordant Violet 5 followed the second pathway. Acid Orange 8 and Acid Orange 7 had the same degradation mechanism as the first degradation mechanism for Mordant Violet 5, that is cleavage of azo bond at the naphthalene ring side where benzenesulfonic acid and 1,2-naphthoquinone are formed.
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Affiliation(s)
- Yiping Lu
- Department of Textiles, Merchandising, & Interiors, University of Georgia, Athens, GA 30602-3622, USA.
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24
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Phillips DR, Krishnan H, Watson J. First UK report of successful treatment of Mycobacterium simiae and immune reconstitution inflammatory syndrome in an HIV-seropositive patient. Sex Transm Infect 2008; 84:271-2. [DOI: 10.1136/sti.2008.029900] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
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25
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Abstract
AIMS To investigate antibiotic production by bacteria isolated from the hindgut of Tipula abdominalis, the aquatic crane fly. METHODS AND RESULTS A group of five isolates with 99.1% 16S rRNA sequence similarity to Paenibacillus amylolyticus were identified as antibacterial producers using the cross-streak method against both Gram-positive and Gram-negative bacteria. For one isolate, P. amylolyticus C27, biochemical tests were performed to confirm 16S rRNA identification and the antibacterials were purified using chromatographic methods. Postsource decay (PSD) mass spectroscopy (MS) was used to identify the antimicrobials, which were found to be polymyxins E(1) and E(2). Investigation of the remaining four isolates using PSD MS revealed they all produce polymyxins E(1) and E(2) as well. CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY Although variants of the polymyxin antibiotics are known to be produced by several species within the Paenibacillus genus, this first investigation of antibacterial production by bacteria isolated from the hindgut of T. abdominalis describes a novel source for polymyxin E production as well as the first report of antibiotic production by P. amylolyticus.
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26
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Zhao X, Lu Y, Phillips DR, Hwang HM, Hardin IR. Study of biodegradation products from azo dyes in fungal degradation by capillary electrophoresis/electrospray mass spectrometry. J Chromatogr A 2007; 1159:217-24. [PMID: 17126346 DOI: 10.1016/j.chroma.2006.10.072] [Citation(s) in RCA: 29] [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] [Subscribe] [Scholar Register] [Received: 08/22/2006] [Revised: 10/17/2006] [Accepted: 10/30/2006] [Indexed: 11/28/2022]
Abstract
Biodegradation products from four model sulfonated azo dyes Orange II, Acid Orange 8, Food Yellow 3, and 4-[(4-hydroxyphenyl)azo]-benzenesulfonic acid, sodium salt (4HABA), during fungal degradation were determined by capillary electrophoresis coupled with ion trap mass spectrometry (CE-MS) with electrospray ionization and a coaxial sheath flow interface. The development and optimization of this analytical method including the sheath liquid composition and flow rate, nebulizing gas flow rate, carrier electrolyte, and MS voltage are described herein. Detection of unknown biodegradation products was carried out under negative ion mode with base peak electrophorogram (BPE) or extractive ion electrophorogram (EIE) monitoring. A volatile ammonium acetate buffer (10 mM) without organic modifier and a shealth liquid made from 2-propanol and water (80:20, v/v) were suited for the separation and ESI interface. The sulfonated ion was the base peak for model azo dyes and their metabolites containing sulfonic group. Results showed that the tested azo dyes were degraded quickly in the culture of white rot fungus, Pleurotus ostreatus in 3 days with the major biodegradation products being 4-hydroxy-benzenesulfonic acid, 3-methyl-4-hydroxy-benzenesulfonic acid, benzenesulfonic acid, 1,2-naphthoquinone-6-sulfonic acid and 3-methyl-benzenesulfonic acid.
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Affiliation(s)
- Xueheng Zhao
- Department of Biology, Jackson State University, Jackson, MS 39217, USA.
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Rephaeli A, Waks-Yona S, Nudelman A, Tarasenko I, Tarasenko N, Phillips DR, Cutts SM, Kessler-Icekson G. Anticancer prodrugs of butyric acid and formaldehyde protect against doxorubicin-induced cardiotoxicity. Br J Cancer 2007; 96:1667-74. [PMID: 17473824 PMCID: PMC2359917 DOI: 10.1038/sj.bjc.6603781] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Revised: 04/04/2007] [Accepted: 04/12/2007] [Indexed: 12/02/2022] Open
Abstract
Formaldehyde has been previously shown to play a dominant role in promoting synergy between doxorubicin (Dox) and formaldehyde-releasing butyric acid (BA) prodrugs in killing cancer cells. In this work, we report that these prodrugs also protect neonatal rat cardiomyocytes and adult mice against toxicity elicited by Dox. In cardiomyocytes treated with Dox, the formaldehyde releasing prodrugs butyroyloxymethyl diethylphosphate (AN-7) and butyroyloxymethyl butyrate (AN-1), but not the corresponding acetaldehyde-releasing butyroyloxydiethyl phosphate (AN-88) or butyroyloxyethyl butyrate (AN-11), reduced lactate dehydrogenase leakage, prevented loss of mitochondrial membrane potential (DeltaPsim) and attenuated upregulation of the proapoptotic gene Bax. In Dox-treated mice, AN-7 but not AN-88 attenuated weight-loss and mortality, and increase in serum lactate dehydrogenase. These findings show that BA prodrugs that release formaldehyde and augment Dox anticancer activity also protect against Dox cardiotoxicity. Based on these observations, clinical applications of these prodrugs for patients treated with Dox warrant further investigation.
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Affiliation(s)
- A Rephaeli
- Sackler Faculty of Medicine, Felsenstein Medical Research Center, Tel-Aviv University, Beilinson Campus, Petach-Tikva, 49100, Israel.
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Gårdestig A, Phillips DR. How low-energy weak reactions can constrain three-nucleon forces and the neutron-neutron scattering length. Phys Rev Lett 2006; 96:232301. [PMID: 16803373 DOI: 10.1103/physrevlett.96.232301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2006] [Indexed: 05/10/2023]
Abstract
We show that chiral symmetry and gauge invariance enforce relations between the short-distance physics that occurs in a number of electroweak and pionic reactions on light nuclei. Within chiral perturbation theory, this is manifested via the appearance of the same axial isovector two-body contact term in pi(-)d --> nngamma, p-wave pion production in NN collisions, tritium beta decay, pp fusion, nud scattering, and the hep reaction. Using a Gamow-Teller matrix element obtained from calculations of pp fusion as input, we compute the neutron spectrum obtained in pi(-)d --> nngamma. With the short-distance physics in this process controlled from pp --> de(=)nu(e), the theoretical uncertainty in the nn scattering length extracted from pi(-)d --> nngamma is reduced by a factor larger than 3, to approximately < or = 0.05 fm.
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Affiliation(s)
- A Gårdestig
- Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701, USA.
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Affiliation(s)
- A T Nurden
- Institut Fédératif de Recherche 4, CHU Bordeaux, Pessac, France
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Cutts SM, Swift LP, Rephaeli A, Nudelman A, Phillips DR. Recent Advances in Understanding and Exploiting the Activation of Anthracyclines by Formaldehyde. ACTA ACUST UNITED AC 2005; 5:431-47. [PMID: 16178771 DOI: 10.2174/1568011054866964] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The anthracycline group of compounds are amongst the most effective chemotherapy agents currently in use for cancer treatment. They are generally classified as topoisomerase II inhibitors but also have a variety of other targets in cells. It has been known for some years that the anthracyclines are capable of forming DNA adducts, but the relevance and extent of these DNA adducts in cells and their role in causing cell death has remained obscure. When the adduct structure was solved, it became clear that formaldehyde was an absolute requirement for adduct formation. This led to a renewed interest in the capacity of anthracyclines to form DNA adducts, and there are now several ways in which adduct formation can be facilitated in cells. These involve strategies to provide the requisite formaldehyde in the form of anthracycline-formaldehyde conjugates, and the use of formaldehyde-releasing drugs in combination with anthracyclines. Of particular interest is the new therapeutic compound AN-9 that releases both butyric acid and formaldehyde, leading to efficient anthracycline-DNA adduct formation, and synergy between the two compounds. Targeted formation of adducts using anthracycline-formaldehyde conjugates tethered to cell surface targeted molecules is now also possible. Some of the cellular consequences of these adducts have now been studied, and it appears that their formation can overcome anthracycline-resistance mechanisms, and that they are more efficient at inducing apoptosis than when functioning primarily through impairment of topoisomerase II. The clinical application of the use of anthracyclines as DNA adduct forming agents is now being explored.
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Affiliation(s)
- S M Cutts
- Department of Biochemistry, La Trobe University, Victoria 3086, Australia.
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Abstract
The current standard of care for the treatment of arterial thrombosis includes anticoagulants and three classes of antiplatelet agents--aspirin, thienopyridines and glycoprotein IIb-IIIa antagonists. Although these drugs have had a significant impact on morbidity and mortality in several patient populations, up to 15% of the high risk patients with acute coronary syndrome continue to suffer from ischemic events. This problem may occur, in part, because the platelets in many patients are non-responsive to aspirin and clopidogrel. Murine models now indicate that platelets are not only responsible for arterial occlusion, they are also involved in the progression of atherosclerotic disease. New opportunities have emerged identifying potential targets and strategies for drug discovery suited to address these deficiencies by more effectively modulating platelet adhesion, thrombus growth, thrombus stability and the pro-inflammatory activity of platelets. In addition, a growing need has emerged for the development of bedside devices capable of bringing personalized medicine to patients being treated with antithrombotic drugs in order to measure the pharmacodynamic activities of new therapies, to assess the activities achieved by combined antithrombotic therapy, and to identify patients that fail to respond.
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Affiliation(s)
- D R Phillips
- Portola Pharmaceuticals, Inc., San Francisco, CA 94402, USA.
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32
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Abstract
A molecular-dynamics model for crack propagation under steady-state conditions is used to study dynamic instabilities along a grain boundary in aluminum that occur when the crack speed approaches 1/3 of the material's Rayleigh wave speed. Instead of crack branching, as is characteristic for a crack propagating in a homogeneous environment, the instability of an intergranular crack results in a periodic series of dislocation bursts. These bursts limit the crack speed and produce velocity oscillations with a large increase in energy dissipation that increases the grain boundary toughness.
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Affiliation(s)
- V Yamakov
- National Institute of Aerospace, Hampton, Virginia 23666, USA.
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Kim YK, Phillips DR, Chao T, Ehrman L. Developmental Isolation and Subsequent Adult Behavior of Drosophila paulistorum. VI. Quantitative Variation in Cuticular Hydrocarbons. Behav Genet 2004; 34:385-94. [PMID: 15082936 DOI: 10.1023/b:bege.0000023644.87050.1a] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Our previous studies have demonstrated that long-term chemical contact with heterospecifics during development minimized unproductive heterospecific matings among the six Drosophila paulistorum semispecies. When socially isolated from conspecifics, discrimination significantly decreased so that more ultimately unproductive heterospecific matings occurred. Such results suggest that learning and social experiences play roles in mate recognition, using chemical information. In investigations into the development of discriminatory behavior in D. paulistorum, social experiences influence the production of cuticular hydrocarbons in both sexes among the six different semispecies of D. paulistorum. Produced by both sexes, 2-methyl triacontane has been detected from egg stages on, gradually increasing with age. However, 11-docosenyl acetate, a male pheromone, was not produced until early adult stages. There were consistent significant differences in quantities and ratios of each of these hydrocarbons among the six semispecies, contributing to their reproductive isolation. Furthermore, we found significant quantitative differences in hydrocarbons between socially isolated flies and communally raised ones: Socially isolated flies produced significantly greater quantities of hydrocarbons than communally raised flies, consistent with previous behavioral data, as isolated flies court more vigorously and often.
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Affiliation(s)
- Yong-Kyu Kim
- Department of Genetics, University of Georgia, Athens, Georgia 30602, USA.
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Abstract
The majority of China's population lives in rural areas and a pattern is emerging of very uneven provision of support for rural elderly people. Local economic conditions and broad demographic trends are creating diversity in the ability both of rural families to care for their elderly kin and in the capacity of communities to support their elderly residents and family carers. In part as a consequence of China's population policy and the 'one-child policy', future Chinese families will have fewer members and be 'older', but they will continue to be regarded emotionally and in policy as the main source of economic and social support for the elderly. The increasing involvement of women in the paid workforce and the changing geographical distribution of family members resulting from work-related migration, are reducing the ability of families to care for their elderly relatives. The availability of resources other than the family for the care of older persons therefore becomes a key issue. Communities in more prosperous, modernising rural areas are often able to provide their elderly residents with welfare and social benefits previously found almost exclusively in urban areas. However, in poorly developed rural areas, provision is either very patchy or non-existent and the local economy cannot support expansion or improvement. A case study in Zhejiang Province illustrates the favourable provision for ageing in a prosperous modernising rural community, in which entitled elderly residents are provided with an impressive array of financial and social benefits. The paper concludes with a consideration of the policy implications of the growing differentiation of the social and economic capacity of rural communities to support their elderly members.
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Affiliation(s)
- A E Joseph
- Department of Geography, University of Guelph, Guelph, Ontario, Canada
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35
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Affiliation(s)
- D R Phillips
- Department of Biochemistry, La Trobe University, Bundoora, Victoria, Australia
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Kirkor E, Gebicki J, Phillips DR, Michl J. Incorporation of neutral molecules into alkali halides (salting). Room-temperature composites from normally immiscible components and room-temperature matrix isolation. J Am Chem Soc 2002. [DOI: 10.1021/ja00282a046] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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McDonald LA, Foster MP, Phillips DR, Ireland CM, Lee AY, Clardy J. Tawicyclamides A and B, new cyclic peptides from the Ascidian Lissoclinum patella: studies on the solution- and solid-state conformations. J Org Chem 2002. [DOI: 10.1021/jo00043a017] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Cowell IM, Phillips DR. Effectiveness of manipulative physiotherapy for the treatment of a neurogenic cervicobrachial pain syndrome: a single case study -- experimental design. Man Ther 2002; 7:31-8. [PMID: 11884154 DOI: 10.1054/math.2001.0429] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A single case study ABC design was used to evaluate the effectiveness of manipulative physiotherapy in a 44-year-old woman with an 8-month history of neurogenic cervicobrachial pain. Clinical examination demonstrated significant signs of upper quadrant neural tissue mechanosensitivity indicating that neural tissue was the dominant tissue of origin for the subject's complaint of pain. Magnetic resonance imaging revealed correlating discal pathology at the C5/6 intersegmental level. The study involved a 4-week pre-assessment phase, a 4-week treatment phase and a 2-week home exercise phase. Functional disability was measured using the Northwick Park Neck Pain Questionnaire and pain was assessed using the McGill Short Form Pain Questionnaire. Cervical motion was measured by a cervical range of motion device (CROM) and the range of shoulder abduction with a mediclino inclinometer. Manipulative physiotherapy treatment involved a cervical lateral glide mobilization technique. Following treatment, visual analysis revealed beneficial effects on pain, functional disability as well as cervical and shoulder mobility. These improvements were maintained over the home exercise phase and at 1-month follow-up. The single case limits generalization of the findings, but the results support previous studies in this area and gives further impetus to controlled clinical trials.
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Affiliation(s)
- I M Cowell
- Chigwell Physiotherapy Clinic, Essex, UK.
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Abstract
The anthracycline Adriamycin is known to form adducts with DNA, but requires prior activation by formaldehyde. In contrast, the anthracycline barminomycin is also able to form adducts with DNA, but does not require activation by formaldehyde. Barminomycin, therefore, appears to function as a pre-activated form of Adriamycin. The DNA adducts formed by both anthracyclines are bound covalently to only one strand of DNA, but both also stabilise duplex DNA sufficiently that they can be detected as virtual interstrand crosslinks in heat denaturation electrophoretic crosslinking assays. The barminomycin-DNA adducts form extremely rapidly with DNA, and at exceedingly low concentrations (approximately 50-fold lower than with Adriamycin in the presence of excess formaldehyde), both characteristics consistent with barminomycin being in a pre-activated state, hence, undergoing a bimolecular reaction with DNA compared with the trimolecular reaction (drug, formaldehyde and DNA) required with Adriamycin. Surprisingly, barminomycin-DNA adducts are substantially more stable (essentially irreversible) than Adriamycin-DNA adducts (half life of approximately 25 h at 37 degrees C). Due to this understanding of the reactivity of barminomycin and its exceptional cytotoxicity (1000-fold more cytotoxic than Adriamycin), detailed structural studies of barminomycin-DNA adducts are now warranted, both in vitro and in tumour cells.
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Affiliation(s)
- M A Moufarij
- Department of Biochemistry, La Trobe University, Bundoora, Vic. 3083, Australia
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Cutts SM, Rephaeli A, Nudelman A, Hmelnitsky I, Phillips DR. Molecular basis for the synergistic interaction of adriamycin with the formaldehyde-releasing prodrug pivaloyloxymethyl butyrate (AN-9). Cancer Res 2001; 61:8194-202. [PMID: 11719450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Abstract
The interaction of Adriamycin and pivaloyloxymethyl butyrate (AN-9) was investigated in IMR-32 neuroblastoma and MCF-7 breast adenocarcinoma cells. Adriamycin is a widely used anticancer drug, whereas AN-9 is an anticancer agent presently undergoing Phase II clinical trials. The anticancer activity of AN-9 has been attributed to its ability to act as a butyric acid prodrug, although it also releases formaldehyde and pivalic acid. Adriamycin and AN-9 in combination display synergy when exposed simultaneously to cells or when AN-9 treatment is up to 18 h after Adriamycin administration. However, the reverse order of addition results in antagonism. These interactions have been established using cell viability assays and classical isobologram analysis. To understand the molecular basis of this synergy, the relative levels of Adriamycin-DNA adducts were determined using various treatment combinations. Levels of Adriamycin-DNA adducts were enhanced when treatment combinations known to be synergistic were used and were diminished using those treatments known to be antagonistic. The relative timing of the addition of Adriamycin and AN-9 was critical, with a 20-fold enhancement of Adriamycin-DNA adducts occurring when AN-9 was administered 2 h after the exposure of cells to Adriamycin. The enhanced levels of these adducts and the accompanying decreased cell viability were directly related to the esterase-dependent release of formaldehyde from AN-9, providing evidence for the formaldehyde-mediated activation of Adriamycin.
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Affiliation(s)
- S M Cutts
- Department of Biochemistry, La Trobe University, Victoria 3086, Australia
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Abstract
BACKGROUND There is strong evidence to suggest that the prevalence of atopic eczema is increasing in developed countries. Environmental factors have been implicated in the disease. OBJECTIVES This descriptive case-control study sheds light on the possible association between atopic eczema in school children and various home environmental factors, and generates hypotheses for further studies. METHODS The study uses data on reported atopic eczema symptoms collected via a cross-sectional parental postal survey (n = 1350) in Nottingham, U.K. Estimates of the risk of reported eczema associated with various home environmental factors were calculated by means of odds ratios (OR), along with population attributable risk percentages. RESULTS The study showed statistically significant associations between atopic eczema symptoms and dampness in the home [OR 1.40; 95% confidence interval (CI) 1.00-1.97], the use of a radiator to heat the child's bedroom (OR 1.50; 95% CI 1.05-2.16) and the use of synthetic pillows (OR 1.51; 95% CI 1.01-2.28). Frequent vacuuming in the home was associated with a decreased prevalence of atopic eczema (OR 0.74; 95% CI 0.58-0.94). The associations with dampness in the home, synthetic pillows and frequency of vacuuming were not altered significantly after adjustment for age, sex and socio-economic status. Population attributable risk percentages for the use of a radiator and synthetic pillows indicate that although the relative risk estimates for these factors may be small, the population impact of these factors is considerable (26% and 28%, respectively), owing to the high prevalence of exposure to these factors among this group of school children. CONCLUSIONS Further research is needed to confirm these associations and additional research is needed to see whether they might be causative. Practical public health advice about the importance of controlling the home environment may then be targeted at families with atopic eczema.
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Affiliation(s)
- N J McNally
- Research & Development Directorate, University College London Hospitals NHS Trust, 1st Floor, Vezey Strong Wing, 112 Hampstead Road, London, NW1 2LT, UK
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Abstract
The beta 3 integrin cytoplasmic tyrosine (ICY) motif of alpha IIb beta 3 becomes tyrosine phosphorylated during platelet aggregation, causing Shc and myosin to interact with the beta-integrin cytoplasmic domain. Platelets from mice lacking beta 3 ICY motif tyrosines formed defective aggregates and poorly retracted clots, establishing integrin tyrosine phosphorylation as a key mediator of beta 3-integrin signals.
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Affiliation(s)
- D R Phillips
- COR Therapeutics, Inc., 256 East Grand Avenue, South San Francisco, California 94080, USA.
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Kereiakes DJ, Lorenz T, Young JJ, Kukielka G, Mueller MN, Nanniazzi-Alaimo L, Phillips DR. Differential effects of citrate versus PPACK anticoagulation on measured platelet inhibition by abciximab, eptifibatide and tirofiban. J Thromb Thrombolysis 2001; 12:123-7. [PMID: 11729363 DOI: 10.1023/a:1012991303381] [Citation(s) in RCA: 25] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
BACKGROUND High levels of glycoprotein (GP) IIb/IIIa receptor inhibition are required to prevent arterial thrombosis following percutaneous coronary intervention. Ex-vivo turbidometric platelet aggregation in citrate anticoagulated blood samples has been the primary method previously utilized to derive dose regimens for administering platelet GP IIb/IIIa inhibitors. Enhanced GP IIb/IIIa binding and inhibition of platelet aggregation for eptifibatide secondary to citrate induced reduction of ionized plasma calcium concentrations has been reported. METHODS/RESULTS We evaluated the differential effects of citrate versus PPACK anticoagulation on turbidometric platelet inhibition in normal volunteers by eptifibatide, tirofiban or abciximab. The decrease in ionized calcium afforded by citrate was associated with enhanced in vitro platelet inhibition for all three GP IIb/IIIa inhibitors, including abciximab. The magnitude of citrate effect was greatest for eptifibatide. Both tirofiban and abciximab have similar citrate calcium chelation associated enhancement of measured platelet inhibition. CONCLUSION Accurate assessment and comparison of platelet inhibition by GP IIb/IIIa inhibitors may require avoidance of calcium chelating anticoagulants.
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Affiliation(s)
- D J Kereiakes
- The Carl and Edyth Lindner Center for Research and Education, 2123 Auburn Avenue, Suite 424, Cincinnati, OH 45219, USA.
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Phillips DR, Cutts SM, Cullinane CM, Crothers DM. High-resolution transcription assay for probing drug-DNA interactions at individual drug sites. Methods Enzymol 2001; 340:466-85. [PMID: 11494864 DOI: 10.1016/s0076-6879(01)40437-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- D R Phillips
- Department of Biochemistry, LaTrobe University, Bundoora, Victoria 3083, Australia
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Abstract
The glycoprotein (GP) Ib-V-IX complex plays a critical role in initiating platelet adhesion to von Willebrand factor (vWF) at the site of vascular injury. The complex also forms a high-affinity binding site for thrombin. Using an intravital microscopy mouse model, it was previously established that vWF plays a critical role in mediating platelet adhesion and thrombus formation following mesenteric arteriolar injury induced by ferric chloride. Further characterization of this model showed that these thrombotic events were also thrombin dependent. Using this vWF- and thrombin-dependent model, this study shows that GP V gene deficiency significantly accelerates both platelet adhesion and thrombus formation in mice following arteriolar injury. The time required for vessel occlusion in GP V-deficient (GP V(-/-)) mice was significantly shorter than that in wild-type mice. Interestingly, large emboli were also produced in GP V(-/-) mice, but not in wild-type mice, causing frequent downstream occlusion. However, when the 2 genotypes were compared in the in vitro perfusion chamber where thrombin was inhibited by heparin, no significant differences were found in either initial single-platelet adhesion or thrombus volume. These results demonstrate that GP V(-/-) mice have accelerated thrombus growth in response to vascular injury and suggest that this is caused by enhanced thrombin-induced platelet activation rather than enhanced binding of GPIb-V-IX to vWF. Absence of GP V also compromises thrombus stability.
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Affiliation(s)
- H Ni
- Center for Blood Research and Department of Pathology, Harvard Medical School, Boston, MA 02115, USA
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47
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Phillips DR, Nannizzi-Alaimo L, Prasad KS. Beta3 tyrosine phosphorylation in alphaIIbbeta3 (platelet membrane GP IIb-IIIa) outside-in integrin signaling. Thromb Haemost 2001; 86:246-58. [PMID: 11487013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
Abstract
The platelet integrin alphaIIbbeta3 not only binds fibrinogen and von Willebrand factor to mediate platelet aggregation and adhesion, it also serves as a signaling receptor. Platelet agonists such as ADP, thrombin and collagen induce "inside-out" signaling which activates the receptor function of alphaIIbbeta3 for soluble fibrinogen. Subsequent platelet aggregation leads to "outside-in" signaling, inducing platelet aggregate stabilization and triggering a variety of functions important to platelet physiology. This review focuses on the role of beta3 tyrosine phosphorylation in alphaIIbbeta3 outside-in signaling. Tyrosine phosphorylation of beta3 in platelets is a dynamic process which is initiated upon platelet aggregation and also by adhesion of platelets to immobilized fibrinogen. Tyrosine phosphorylation occurs on the beta3 integrin cytoplasmic tyrosine (ICY) domain, a conserved motif found in the beta subunits of several integrins. Beta3 ICY domain tyrosine phosphorylation induces the recruitment of two proteins to the cytoplasmic domains of alphaIIbbeta3: the cytoskeletal protein myosin, important to clot retraction; and the signaling adapter protein Shc, important to platelet stimulation, The critical role of beta3 tyrosine phosphorylation to platelet function was established by the diYF mouse, a novel strain which expresses an alphaIIbbeta3 in which the two beta3 ICY domain tyrosines have been mutated to phenylalanine. These mice are selectively impaired in outside-in alphaIIbbeta3 signaling, with defective aggregation and clot-retraction responses in vitro, and an in vivo bleeding defect which is characterized by a pronounced tendency to rebleed. Taken together, the data suggest that the beta3 tyrosine phosphorylation signaling mechanism is important to alphaIIbbeta3 function and might be applicable to a wide variety of integrin-mediated events.
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Affiliation(s)
- D R Phillips
- COR Therapeutics, Inc., South San Francisco, CA 94080, USA.
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Abstract
Recently, we have shown that mitoxantrone can be activated by formaldehyde in vitro to form DNA adducts that are specific for CpG and CpA sites in DNA. The CpG specificity of adduct formation prompted investigations into the effect of cytosine methylation (CpG) on adduct formation, since the majority of CpG dinucleotides in the mammalian genome are methylated and hypermethylation in subsets of genes is associated with various neoplasms. Upon methylation of a 512-base pair DNA fragment (containing the lac UV5 promoter) using HpaII methylase, three CCGG sites downstream of the promoter were methylated at C5 of the internal cytosine residue. In vitro transcription studies of mitoxantrone-reacted DNA revealed a 3-fold enhancement in transcriptional blockage (and hence adduct formation) exclusively at these methylated sites. In vitro cross-linking assays also revealed that methylation enhanced mitoxantrone adduct formation by 2-3-fold, and methylation of cytosine at a single potential drug binding site on a duplex oligonucleotide also enhanced adduct levels by 3-fold. Collectively, these results indicate preferential adduct formation at methylated CpG sites. However, adducts at these methylated sites exhibited the same stability as nonmethylated sites, suggesting that cytosine methylation increases drug accessibility to DNA rather than being involved in kinetic stabilization of the adduct.
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Affiliation(s)
- B S Parker
- Department of Biochemistry, LaTrobe University, Victoria 3086, Australia
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Talarico T, Cullinane CM, Gray PJ, Webster LK, Deacon GB, Phillips DR. Nuclear and mitochondrial distribution of organoamidoplatinum(II) lesions in cisplatin-sensitive and -resistant adenocarcinoma cells. Anticancer Drug Des 2001; 16:135-41. [PMID: 11962511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Abstract
The DNA binding pattern of the organoamidoplatinum(II) compound 1a is of considerable interest because of its known activity against cisplatin-resistant cells. The activity of 1a appears to be due at least in part to a greater cellular uptake than cisplatin into cisplatin-resistant cells, but little is known of the DNA reactions of the organoamidoplatinum(II) compounds. In this study the level of DNA cross-linking and total DNA lesions formed by 1 a were measured by gene-specific Southern hybridization cross-linking assays and by quantitative PCR in cisplatin-sensitive (2008) and in cisplatin-resistant 2008/R human adenocarcinoma cell lines. The surprising result was that the major difference between cisplatin and 1a was that the number of interstrand cross-links induced by 1a were approximately 5-fold greater than that induced by cisplatin in the nuclear (but not mitochondrial) DNA of resistant cells, even though the total number of lesions were essentially the same in both sensitive and resistant cells. This result suggests that the extent of interstrand cross-linking is a critical determinant of the cellular response to 1a and that the enhanced uptake of 1a into resistant cells results in this elevated level of cross-linking, leading to good activity of 1a against cisplatin-resistant cells. It remains unclear as to why 1a exhibits such selective damage to nuclear DNA, and insight into the molecular aspects of this selectivity will provide new opportunities for the further development of new platinum-based agents with activity against cisplatin-resistant cells.
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Affiliation(s)
- T Talarico
- Victorian Cancer Cytogenetics Service, St Vincent's Hospital, Fitzroy, Australia
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Abstract
The non-covalent binding of [(en)Pt(mu-dpzm)2Pt(en)]4+ to segments of DNA containing only G and C bases has been studied to gain an understanding of the pre-covalent binding association of cationic polynuclear platinum(II) anti-cancer drugs at G/C sites. 1H-NMR and CD spectroscopy were used to study the binding of the metal complex to the oligonucleotide d(GC)5 and the polynucleotide poly(dG-dC).poly(dG-dC), respectively. NOE contacts between the metal complex protons and the oligonucleotide sugar H1' protons observed in NOESY spectra indicated that the metal complex bound in the minor groove at the central C4 to G7 region of the oligonucleotide. This result indicates that even though cationic polynuclear platinum(II) complexes bind covalently in the major groove at G/C sites, the pre-covalent binding association is favoured in the minor groove. CD spectra indicated that the addition of the metal complex to poly(dG-dC)-poly(dG-dC) induced some conformational changes, but it was not possible to conclude that [(en)Pt(mu-dpzm)2Pt(en)]4+ induced a B- to Z-type DNA transition. In addition, in vitro transcription assays using the lac UV5 promoter showed that the non-covalent binding of [(en)Pt(mu-dpzm)2Pt(en)]4+ was sufficiently stable to inhibit transcription, and at particular sites.
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Affiliation(s)
- N J Wheate
- School of Chemistry, University College, University of New South Wales, Australian Defence Force Academy, Canberra
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