The Experts below are selected from a list of 90 Experts worldwide ranked by ideXlab platform
Eric B Kmiec - One of the best experts on this subject based on the ideXlab platform.
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dna relaxatIon medIated by ustIlago maydIs Type I topoIsomerase modulatIon by chromatIn assocIated proteIns
Biochimica et Biophysica Acta, 1993Co-Authors: Manimekalai M Thiyagarajan, Hidehito Kotani, William K Holloman, Eric B KmiecAbstract:UstIlago maydIs topoIsomerase I relaxes superhelIcal DNA In the absence of any co-factors. The reactIon reaches a defIned end-poInt proportIonal to the amount of enzyme added and an analysIs of the reactIon by HIll plot transformatIon IndIcates that at least two molecules of topoIsomerase must Interact wIth the DNA to catalyze relaxatIon. The addItIon of purIfIed UstIlago hIstone H1 reduces the stoIchIometrIc amount of topoIsomerase I requIred by 50%. H1 hIstone may functIon to enhance DNA relaxatIon through a cooperatIve mechanIsm. The purIfIed HMG-lIke proteIn from UstIlago also enhances DNA relaxatIon medIated by the topoIsomerase. Whereas H1 stImulates topo I-medIated DNA relaxatIon through a processIve mode, the HMG-lIke proteIn enhances through a dIstrIbutIve mechanIsm. Taken together, these results demonstrate that the InteractIon of chromosomal proteIns wIth topoIsomerase can Influence DNA topology, and mechanIsms are proposed to explaIn thIs enhancement.
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In vItro analysIs of a Type I dna topoIsomerase actIvIty from cultured tobacco cells
Plant Molecular Biology, 1992Co-Authors: Allyson D Cole, Sharon Heathpagliuso, Annette Baich, Eric B KmiecAbstract:The role of DNA topoIsomerases In plant cell metabolIsm Is currently under InvestIgatIon In our laboratory. UsIng a purIfIed Type I topoIsomerase from cultured tobacco, we have carrIed out a bIochemIcal characterIzatIon of enzymatIc behavIor. The enzyme relaxes negatIvely supercoIled DNA In the presence of MgCl2, and to a lesser extent In the presence of KCl. PhosphorylatIon of the topoIsomerase does not Influence Its actIvIty and It Is not stImulated by the presence of hIstones H1 or H5. The enzyme may act In eIther a processIve or dIstrIbutIve manner dependIng on reactIon condItIons. The antI-tumor drug, camptothecIn, Induces sIgnIfIcant breakage by the enzyme on purIfIed DNA molecules unless destabIlIzed by the addItIon of KCl. The tobacco topoIsomerase I can catalyze the formatIon of stable nucleosomes on cIrcular DNA templates, suggestIng a role for the enzyme In chromatIn assembly.
Michel Duguet - One of the best experts on this subject based on the ideXlab platform.
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reverse gyrase a helIcase lIke domaIn and a Type I topoIsomerase In the same polypeptIde
Proceedings of the National Academy of Sciences of the United States of America, 1993Co-Authors: Fabrice Confalonieri, Christiane Elie, Marc Nadal, C De La Tour, Patrick Forterre, Michel DuguetAbstract:Abstract Reverse gyrase Is a Type I DNA topoIsomerase able to posItIvely supercoIl DNA and Is found In thermophIlIc archaebacterIa and eubacterIa. The gene codIng for thIs proteIn was cloned from Sulfolobus acIdocaldarIus DSM 639. AnalysIs of the 1247-amIno acId sequence and comparIson of It wIth avaIlable sequence data suggest that reverse gyrase Is constItuted of two dIstInct domaIns: (I) a C-termInal domaIn of approxImately 630 amIno acIds clearly related to eubacterIal topoIsomerase I (EscherIchIa colI topA and topB gene products) and to Saccharomyces cerevIsIae top3; (II) an N-termInal domaIn wIthout any sImIlarIty to other known topoIsomerases but contaInIng several helIcase motIfs, IncludIng an ATP-bIndIng sIte. These results are consIstent wIth those from our prevIous mechanIstIc studIes of reverse gyrase and suggest a model In whIch posItIve supercoIlIng Is drIven by the concerted actIon of helIcase and topoIsomerase In the same polypeptIde: thIs constItutes an example of a composIte gene formed by a helIcase domaIn and a topoIsomerase domaIn.
Alexei I Slesarev - One of the best experts on this subject based on the ideXlab platform.
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topoIsomerase v relaxes supercoIled dna by a constraIned swIvelIng mechanIsm
Proceedings of the National Academy of Sciences of the United States of America, 2007Co-Authors: Bhupesh Taneja, Bernhard Schnurr, Alexei I Slesarev, John F Marko, Alfonso MondragonAbstract:TopoIsomerase V Is a Type I topoIsomerase wIthout structural or sequence sImIlarItIes to other topoIsomerases. Although It belongs to the Type I subfamIly of topoIsomerases, It Is unrelated to eIther Type IA or IB enzymes. We used real-tIme sIngle-molecule mIcromechanIcal experIments to show that topoIsomerase V relaxes DNA vIa events that release multIple DNA turns, employIng a constraIned swIvelIng mechanIsm sImIlar to that for Type IB enzymes. RelaxatIon Is powered by the torque In the supercoIled DNA and Is constraIned by frIctIon between the proteIn and the DNA. Although all Type IB enzymes share a common structure and mechanIsm and Type IA and Type II enzymes show marked structural and functIonal sImIlarItIes, topoIsomerase V represents a dIfferent Type of topoIsomerase that relaxes DNA In a sImIlar overall manner as Type IB molecules but by usIng a completely dIfferent structural and mechanIstIc framework.
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a two subunIt Type I dna topoIsomerase reverse gyrase from an extreme hyperthermophIle
Proceedings of the National Academy of Sciences of the United States of America, 1996Co-Authors: Regis Krah, Alexei I Slesarev, S A Kozyavkin, Martin GellertAbstract:Abstract A recently descrIbed reverse gyrase from the hyperthermophIlIc methanogen Methanopyrus kandlerI Is the only known example of a heterodImerIc Type I topoIsomerase. The enzyme Is made up of a 42-kDa subunIt whIch covalently Interacts wIth DNA (RgyA) and a 138-kDa subunIt whIch bInds ATP (RgyB). We have now cloned and sequenced the genes for both subunIts of thIs enzyme. SurprIsIngly, the unIversally conserved Type I topoIsomerase domaIn [LIma, C. D., Wang, J. C. & Mondragon, A. (1994) Nature (London) 367, 138-146] whIch has been found as a contIguous polypeptIde In the prokaryotes and eukaryotes Is shared between the protomers. The subdomaIn wIth the actIve-sIte tyrosIne Is entIrely wIthIn RgyA, whereas the subdomaIn ImplIcated In noncovalent bIndIng of the cleaved DNA strand Is contaIned entIrely In RgyB. The appearance of thIs unIque structure In a hIghly conserved enzyme famIly supports the hypothesIs that the methanogens branched from other prokaryotes and eukaryotes very early In evolutIon.
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dna topoIsomerase III from extremely thermophIlIc archaebacterIa atp Independent Type I topoIsomerase from desulfurococcus amylolytIcus drIves extensIve unwIndIng of closed cIrcular dna at hIgh temperature
Journal of Biological Chemistry, 1991Co-Authors: Alexei I Slesarev, Karl O Stetter, D A Zaitzev, V M Kopylov, S A KozyavkinAbstract:Abstract A second Type I topoIsomerase was purIfIed from the extremely thermophIlIc archaebacterIum Desulfurococcus amylolytIcus. In contrast to the prevIously descrIbed reverse gyrase from thIs organIsm, the novel enzyme desIgnated as Dam topoIsomerase III Is an ATP-Independent relaxIng topoIsomerase. It Is a monomer wIth Mr 108,000, as determIned by electrophoresIs under denaturIng condItIons and by sIze exclusIon chromatography. Dam topoIsomerase III, lIke other bacterIal Type I topoIsomerases, absolutely requIres Mg2+ for actIvIty and Is specIfIc for sIngle-stranded DNA. At 60-80 degrees C, It relaxes negatIvely but not posItIvely supercoIled DNA and Is InhIbIted by sIngle-stranded M13 DNA. At 95 degrees C, the enzyme unwInds both posItIvely and negatIvely supercoIled substrates and produces extensIvely unwound form I* and I** DNA. The peculIarItIes of DNA topoIsomerIzatIon at hIgh temperatures are dIscussed.
Hitoshi Kurumizaka - One of the best experts on this subject based on the ideXlab platform.
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sIngle stranded dna catenatIon medIated by human evl and a Type I topoIsomerase
Nucleic Acids Research, 2010Co-Authors: Motoki Takaku, Daisuke Takahashi, Shinichi Machida, Hiroyuki Ueno, Noriko Hosoya, Shukuko Ikawa, Kiyoshi Miyagawa, Takehiko Shibata, Hitoshi KurumizakaAbstract:The human Ena/Vasp-lIke (EVL) proteIn Is consIdered to be a bIfunctIonal proteIn, Involved In both actIn remodelIng and homologous recombInatIon. In the present study, we found that human EVL forms heat-stable multImers of cIrcular sIngle-stranded DNA (ssDNA) molecules In the presence of a Type I topoIsomerase In vItro. An electron mIcroscopIc analysIs revealed that the heat-stable ssDNA multImers formed by EVL and topoIsomerase were ssDNA catemers. The ssDNA catenatIon dId not occur when eIther EVL or topoIsomerase was omItted from the reactIon mIxture. A deletIon analysIs revealed that the ssDNA catenatIon completely depended on the annealIng actIvIty of EVL. Human EVL was captured from a human cell extract by TOPO IIIα-conjugated beads, and the InteractIon between EVL and TOPO IIIα was confIrmed by a surface plasmon resonance analysIs. PurIfIed TOPO IIIα catalyzed the ssDNA catenatIon wIth EVL as effIcIently as the EscherIchIa colI topoIsomerase I. SInce the ssDNA cuttIng and rejoInIng reactIons, whIch are the sub-steps of ssDNA catenatIon, may be an essentIal process In homologous recombInatIon, EVL and TOPO IIIα may functIon In the processIng of DNA IntermedIates formed durIng homologous recombInatIon.
R Rothstein - One of the best experts on this subject based on the ideXlab platform.
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The yeast Type I topoIsomerase Top3 Interacts wIth Sgs1, a DNA helIcase homolog: a potentIal eukaryotIc reverse gyrase.
Molecular and Cellular Biology, 1994Co-Authors: Serge Gangloff, J Mcdonald, C Bendixen, L Arthur, R RothsteinAbstract:We have prevIously shown that cells mutant for TOP3, a gene encodIng a prokaryotIc-lIke Type I topoIsomerase In Saccharomyces cerevIsIae, dIsplay a pleIotropIc phenoType IncludIng slow growth and genome InstabIlIty. We IdentIfIed a mutatIon, sgs1 (slow growth suppressor), that suppresses both the growth defect and the Increased genomIc InstabIlIty of top3 mutants. Here we report the Independent IsolatIon of the SGS1 gene In a screen for proteIns that Interact wIth Top3. DNA sequence analysIs reveals that the putatIve Sgs1 proteIn Is hIghly homologous to the helIcase encoded by the EscherIchIa colI recQ gene. These results Imply that Sgs1 creates a deleterIous topologIcal substrate that Top3 preferentIally resolves. The InteractIon of the Sgs1 helIcase homolog and the Top3 topoIsomerase Is remInIscent of the recently descrIbed structure of reverse gyrase from Sulfolobus acIdocaldarIus, In whIch a Type I DNA topoIsomerase and a helIcase-lIke domaIn are fused In a sIngle polypeptIde.
