bluuebunny/crossref_metadata_2025_split huggingface dataset:
Xanthosine Utilization in
Salmonella enterica
Serovar Typhimurium Is Recovered by a Single Aspartate-to-Glycine Substitution in Xanthosine Phosphorylase
Authors: Riis Hansen Michael , Tranekjær Jørgensen Jesper , Dandanell Gert 
Published: May 2006

ABSTRACT

xapABR
from
Salmonella enterica
was analyzed and compared with the corresponding
Escherichia coli
genes.
xapB
and
xapR
, but not
xapA
, encode functional proteins. An
S. enterica
XapA(Asp72Gly) mutant that restores the phosphorolytic activity was selected. The purified mutant enzyme has different kinetic constants than the
E. coli
enzyme but similar substrate specificity.
Subcellular Partitioning of Transcription Factors inBacillus subtilis
Authors: Doherty Geoff P. , Meredith Donna H. , Lewis Peter J. 
Published: May 2006

ABSTRACTRNA polymerase (RNAP) requires the interaction of various transcription elongation factors to efficiently transcribe RNA. During transcription of rRNA operons, RNAP forms highly processive antitermination complexes by interacting with NusA, NusB, NusG, NusE, and possibly several unidentified factors to increase elongation rates to around twice those observed for mRNA. In previous work we used cytological assays withBacillus subtilisto identify the major sites of rRNA synthesis within the cell, which are called transcription foci. Using this cytological assay, in conjunction with both quantitative native polyacrylamide gel electrophoresis and Western blotting, we investigated the total protein levels and the ratios of NusB and NusG to RNAP in both antitermination and mRNA transcription complexes. We determined that the ratio of RNAP to NusG was 1:1 in both antitermination and mRNA transcription complexes, suggesting that NusG plays important regulatory roles in both complexes. A ratio of NusB to RNAP of 1:1 was calculated for antitermination complexes with just a 0.3:1 ratio in mRNA complexes, suggesting that NusB is restricted to antitermination complexes. We also investigated the cellular abundance and subcellular localization of transcription restart factor GreA. We found no evidence which suggests that GreA is involved in antitermination complex formation and that it has a cellular abundance which is around twice that of RNAP. Surprisingly, we found that the vast majority of GreA is associated with RNAP, suggesting that there is more than one binding site for GreA on RNAP. These results indicate that transcription elongation complexes are highly dynamic and are differentially segregated within the nucleoid according to their functions.
The Periplasmic Folding of a Cysteineless Autotransporter Passenger Domain Interferes with Its Outer Membrane Translocation
Authors: Rutherford Nancy , Charbonneau Marie-Ève , Berthiaume Frédéric , Betton Jean-Michel , Mourez Michael 
Published: May 2006

ABSTRACTAutotransporters are single polypeptides consisting of an outer membrane translocation domain mediating the translocation of a passenger domain. The periplasmic folding state of the passenger domain is controversial. By comparisons of passenger domains differing in their folding properties, our results suggest that periplasmic folding of passenger domains interferes with translocation.
Escherichia coli
Competence Gene Homologs Are Essential for Competitive Fitness and the Use of DNA as a Nutrient
Authors: Palchevskiy Vyacheslav , Finkel Steven E. 
Published: May 2006

ABSTRACT

Natural genetic competence is the ability of cells to take up extracellular DNA and is an important mechanism for horizontal gene transfer. Another potential benefit of natural competence is that exogenous DNA can serve as a nutrient source for starving bacteria because the ability to “eat” DNA is necessary for competitive survival in environments containing limited nutrients. We show here that eight
Escherichia coli
genes, identified as homologs of
com
genes in
Haemophilus influenzae
and
Neisseria gonorrhoeae
, are necessary for the use of extracellular DNA as the sole source of carbon and energy. These genes also confer a competitive advantage to
E. coli
during long-term stationary-phase incubation. We also show that homologs of these genes are found throughout the proteobacteria, suggesting that the use of DNA as a nutrient may be a widespread phenomenon.
Acquisition and Evolution of theexoULocus inPseudomonas aeruginosa
Authors: Kulasekara Bridget R. , Kulasekara Hemantha D. , Wolfgang Matthew C. , Stevens Lisa , Frank Dara W. , Lory Stephen 
Published: May 2006

ABSTRACTExoU is a potentPseudomonas aeruginosacytotoxin translocated into host cells by the type III secretion system. A comparison of genomes of variousP. aeruginosastrains showed that that the ExoU determinant is found in the same polymorphic region of the chromosome near a tRNALysgene, suggesting thatexoUis a horizontally acquired virulence determinant. We used yeast recombinational cloning to characterize four distinct ExoU-encoding DNA segments. We then sequenced and annotated three of these four genomic regions. The sequence of the largest DNA segment, named ExoU island A, revealed many plasmid- and genomic island-associated genes, most of which have been conserved across a broad set of β- and γ-Proteobacteria. Comparison of the sequenced ExoU-encoding genomic islands to the corresponding PAO1 tRNALys-linked genomic island, the pathogenicity islands of strain PA14, and pKLC102 of clone C strains allowed us to propose a mechanism for the origin and transmission of the ExoU determinant. The evolutionary history very likely involved transposition of the ExoU determinant onto a transmissible plasmid, followed by transfer of the plasmid into differentP. aeruginosastrains. The plasmid subsequently integrated into a tRNALysgene in the chromosome of each recipient, where it acquired insertion sequences and underwent deletions and rearrangements. We have also applied yeast recombinational cloning to facilitate a targeted mutagenesis of ExoU island A, further demonstrating the utility of the specific features of the yeast capture vector for functional analyses of genes on large horizontally acquired genetic elements.
Réponses aux commentaires "Polymérisation du norbornène par des amorceurs au ruthénium. Etude cinétique de la réaction"
Authors: Kiennemann A. 
Published: May 2006

The reaction order (between 0 and 1 or between 1 and 2) of the polymerization of norbornene catalyzed by ruthenium initiators is discussed. The role of the solvent and the effect of pretreatment of the catalyst allow the proposal of a reaction scheme of the dissociative type. [Journal Translation]
Relation entre structure et réactivité dans les réactions d'addition nucléophile sur les dérivés carbonylés: influence de la tension angulaire sur la réactivité de cyclanones et cyclanols angulairement contraints
Authors: Boyer Bernard , Lamaty Gérard , Moreau Claude , Geneste Patrick 
Published: May 2006

The rate constants for addition of sodium borohydride on the angularly constrained cyclic ketones, tricyclo[3.3.1.1.3,7]-2-decanone (1), bicyclo[3.3.1]-9-nonanone (2), bicyclo[3.2.1.])-8-octanone (3), and bicyclo[2.2.1.]-7-heptanone (4), have been determined in water/dioxane (50:50 v/v) at 25 °C. These values demonstrate the energy differences caused by the changes in torsion angles on passing from the initial state to the transition state. The activation energies determined, representing almost all of the energy associated with the angular torsion, are indicative of a late transition state.Comparison of rate constants for the reduction of these ketones where the reaction site carbon changes from sp2 to sp3 hybridization with the rates for chromic acid oxidation of the corresponding alcohols (opposite change of hybridization) demonstrates that the effects of the angular variations can also act as criteria for the determination of the position of transition states along the reaction pathway. [Journal Translation]
Influence complexe d'additifs hydrogénés sur le craquage de substances organiques et analogie hydraulique pour la propagation des chaînes. I. Cas d'une pyrolyse à une seule stoechiométrie
Authors: Scacchi Gérard , Baronnet François , Nlclause Michel 
Published: May 2006

This first article (I) considers the homogeneous pyrolysis at very low conversion of an organic substance, μH, involving a single principal stoichiometry (μH = m + βH) and proceeding by a mechanism in which the chains are propagated by free radicals (β• and μ•) according to the steps:[Formula: see text]The mechanism "μH, YH" of Niclause and co-workers interprets numerous effects of acceleration, or of inhibition, by hydrogenated additives YH, in the pyrolysis of such organic substances μH.A novel hydraulicanalogy is proposed to describe the propagation of chains in these reactions. This analogy immediately permits a better comprehension of the concept of a step which limits the rate of propagation in the decomposition of pure [μH, namely the bimolecular process [3] in the limiting case [A] where [Formula: see text], or the unimolecular process [2] in the limiting case [B] where [Formula: see text]. The analogy also leads to a better understanding of why a pyrolysis which follows the limiting case [A] (e.g. neopentane) may be accelerated by certain hydrogenated additives (HCl, HBr, H2S), while a thermal decomposition following the limiting case [B] (e.g. ethane) cannot be accelerated by any hydrogenated additive according to this mechanism.In a second article (II), the preceding considerations will be extended to the case of an organic substance μH whose decomposition involves several principal primary stoichiometrics. [Journal Translation]
Influence complexe d'additifs hydrogénés sur le craquage de substances organiques et analogie hydraulique pour la propagation des chaînes. II. Cas d'une pyrolyse à plusieurs stoechiométries
Authors: Scacchi Gérard , Juste-Darras Clotilde , Baronnet François , Niclause Mlchel 
Published: May 2006

A first article (I) considered the simple case of an organic substance μH whose decomposition at low conversion follows a single principal stoichiometry: μH = m + βH. An hydraulicanalogy was introduced in order to describe the propagation of chains in the pyrolysis of μH, either pure or in the presence of a hydrogenated substance YH. Applying the mechanism "μH, YH" of Niclause and co-workers, this analogy leads, in particular, to a better understanding of why certain hydrogenated additives accelerate certain thermal decompositions (e.g. neo-C5H12 = i-C4H8 + CH4), whereas no hydrogenated additive accelerates other pyrolyses (e.g. C2H6 = C2H4 + H2).This second article (II) extends the preceding considerations to the more complex case of an organic substance μH which decomposes according to two principal primary stoichiometries:[Formula: see text]It is shown that the generalized mechanism "μH, YH" and the hydraulicanalogy for the propagation of chains permit an interpretation of the influence of hydrogenated additives (HCl, HBr, H2S, H2, C3H6) on the initial rates of the reactions [A] and [B] in the pyrolysis of propane or of isobutane and on the selectivity of this decomposition (the importance of [A] relative to that of [B]). Finally the still more complex case, in which an organic substance μH decomposes according to morethantwo principal primary stoichiometries, is briefly examined. [Journal Translation]
Stéréochimie de diéthylphosphono carbéthoxy-4 pyrrolidines. Étude par rmn du proton à haut champ (250 MHz) et du carbone (13C)
Authors: Rabiller C. , Dehnel A. , Lavielle G. 
Published: May 2006

A series of 2-diethylphosphono 4-carbethoxy pyrrolidines has been studied by 250 MHz 1H nmr and 13C nmr. A study of the chemical shifts allows us to establish the structures and the analysis of the 3JHH, 3JPH and 3JPC coupling constants leads to designation of preferred conformations for these rings. Good agreement is noted between the angular dependence of these coupling constants and the dihedral angles. [Journal Translation]
Étude structurale d'aldimines derivées des furanne-, thiophène- et N-méthylpyrrolecarboxaldéhydes-2.I. N-hétéroarylidèneanilines
Authors: Audoye Paul , Coumes René-Charles , Gaset Antoine , Gorrichon Jean-Pierre 
Published: May 2006

We have studied a series of five N-heteroarylideneanilines, either nitrated or not on the heterocyclic ring, in which the hetero atom can be O, S or N—CH3. The uv and 13C nmr results obtained suggest that these molecules are, as in the case of benzylideneaniline, not entirely planar. In addition, 1H nmr shows that only a single rotamer exists out of the four possibilities (or, at the limit, a rapid equilibrium between two rotamers). [Journal Translation]
Complexes de Cu(II), Co(II), Ni(II) et UO2(II) avec les bases de Schiff N-(4-méthyl-2-pyridyI)salicylaldimine et N-(6-méthyl-2-pyridyl)salicylaldimine
Authors: Capitán-Vallvey L. F. , Jiménez C. , Cuadros L. 
Published: May 2006

We have isolated the complexes of the Schiff bases N-(4-methyl-2-pyridyl)salicylaldimine and N-(6-methyl-2-pyridyl)salicylaldimine with Co(II), Ni(II), Cu(II), and UO2(II) in both aqueous alcoholic and absolute alcoholic solutions. We note different modes of action of these Schiff bases according to the medium used. However, in aqueous alcoholic solution the complexes mentioned have a remarkable capacity for reaction with the substances in solution. We propose two new gravimetric methods for Ni(II) and UO2(II). [Journal Translation]
Méthylhalogénocyclopropanation des éthoxy-alcènes diversement alkylés. Identification stéréochimique des adduits et étude de la stéréosélectivité
Authors: Barlet Roger , Goaller Raymond Le , Gey Claude 
Published: May 2006

Ethoxy-alkenes act as excellent carbene acceptors in the methylmonohalogenocyclopropanation reaction mediated by 1,1-dichloroethane and iodide-ion free methyl iodide. As well as chlorinated adducts, a large proportion of brominated products are obtained by means of halogen exchange at the carbene complex – salt intermediate stage. Adduct stereochemistry is determined by 1H and 13C nmr spectroscopy. The syn-stereoselectivity of the reaction is discussed in electronic and steric terms. [Journal Translation]
Réactivité nucléophile des cyclanones: influence de la stéréochimie cis/trans en série bicyclique
Authors: Agami C. , Rizk T. , Durand R. , Geneste P. 
Published: May 2006

The relative reactivities of a number of cis/trans pairs of bicyclic ketones in the 1- and 2-decalone series (2-decalone; 10-methyl-2-decalone; 9-methyl-1-decalone; and 3,10-dimethyl-2-decalone) have been studied for the nucleophilic addition of hydroxylamine in acidic medium. The results obtained as well as the rate constants for neutral or acid catalysed addition always reveal a slight preference for the trans-isomer (× 2.4). This result agrees with the proposal that preferential equatorial attack of a nucleophile is caused by conformational factors related to a steroid [Formula: see text] non-steroid conformation equilibrium in the cis-isomers. [Journal Translation]
Hypoxia Increases Androgen Receptor Activity in Prostate Cancer Cells
Authors: Park Soo-Yeon , Kim Yun-Jeong , Gao Allen C. , Mohler James L. , Onate Sergio A. , Hidalgo Alejandro A. , Ip Clement , Park Eun-Mi , Yoon Sun Young , Park Young-Mee 
Published: May 2006

Abstract
Recent studies show that prostate cancer cells are able to survive in a hypoxic tumor environment, and the extent of tumor hypoxia correlates with poor clinical outcome. Androgen deprivation, the most common form of prostate cancer therapy, was itself shown to induce a state of transient hypoxia at the microenvironmental level. Because androgen receptor (AR) signaling plays a critical role in prostate cancer, we investigated the effect of hypoxia in regulating AR function. We found that in LNCaP prostate cancer cells, AR binding to the androgen-responsive element (ARE), prostate-specific antigen accumulation, and ARE-reporter gene activity were increased after hypoxia treatment. Hypoxia-enhanced AR function was also observed when AR was exogenously introduced into AR-null DU145 cells. Confocal microscopy and chromatin immunoprecipitation assays showed that AR translocation to the nucleus and AR recruitment to the prostate-specific antigen promoter were facilitated after hypoxia treatment. The AR stimulatory effect seemed to be ligand-dependent because it was abrogated when cells were cultured in an androgen-depleted medium, but was restored with the addition of R1881, a synthetic androgen. The sensitivity of AR activation to R1881 was also increased after hypoxia treatment. Although concentrations of &lt;1 nmol/L R1881 did not induce ARE reporter activity under normoxic conditions, exposure to hypoxia greatly potentiated the AR response to low levels of R1881. Collectively, our results provide compelling evidence that changes in hypoxia/reoxygenation stimulate AR trans-activation and sensitization. The AR-stimulatory effect of an unstable tissue oxygenation milieu of a tumor is likely to contribute to treatment resistance and the emergence of recurrent prostate cancer. (Cancer Res 2006; 66(10): 5121-9)
Protein 4.1B/Differentially Expressed in Adenocarcinoma of the Lung-1 Functions as a Growth Suppressor in Meningioma Cells by Activating Rac1-Dependent c-Jun-NH2-kinase Signaling
Authors: Gerber Mark A. , Bahr Scott M. , Gutmann David H. 
Published: May 2006

Abstract
Meningiomas are the second most common brain tumor in adults, yet comparatively little is presently known about the dysregulated growth control pathways involved in their formation and progression. One of the most frequently observed genetic changes in benign meningioma involves loss of protein 4.1B expression. Previous studies from our laboratory have shown that protein 4.1B growth suppression in meningioma is associated with the activation of the c-Jun-NH2-kinase (JNK) pathway and requires localization of a small unique region (U2 domain) of protein 4.1B to the plasma membrane. To define the relationship between protein 4.1B expression and JNK activation, as well as to determine the mechanism of JNK activation by protein 4.1B, we used a combination of genetic and pharmacologic approaches. In this report, we show that protein 4.1B/differentially expressed in adenocarcinoma of the lung-1 (DAL-1) expression in meningioma cells in vitro results in JNK activation, which requires the sequential activation of Src, Rac1, and JNK. In addition, inhibition of Rac1 or JNK activation abrogates protein 4.1B/DAL-1 growth suppression and cyclin A regulation. Last, protein 4.1B/DAL-1 regulation of this critical growth control pathway in meningioma cells requires the presence of the U2 domain. Collectively, these observations provide the first mechanistic insights into the function of protein 4.1B as a growth regulator in meningioma cells. (Cancer Res 2006; 66(10): 5295-303)
Stromal Antiapoptotic Paracrine Loop in Perineural Invasion of Prostatic Carcinoma
Authors: Ayala Gustavo E. , Dai Hong , Tahir Salahaldin A. , Li Rile , Timme Terry , Ittmann Michael , Frolov Anna , Wheeler Thomas M. , Rowley David , Thompson Timothy C. 
Published: May 2006

Abstract
Caveolin-1 (cav-1) is a major scaffolding component of cell membrane invaginations (caveolae). It is involved in sequestering numerous effectors and signaling molecules and has antiapototic activities in prostate cancer. Perineural invasion (PNI) is associated with decreased apoptosis of cancer cells both in human tissues and the in vitro PNI model. We show here that stromal (perineurium) production of cav-1 is involved in a paracrine antiapoptotic loop in PNI. Transforming growth factor-β1 is up-regulated in the cancer cells as they approach the nerve and is thought to up-regulate cav-1 in the perineurium of nerves with prostate cancer. Cav-1 is then secreted into the microenvironment and used by prostate cancer cells to inhibit apoptosis. In the in vitro PNI model, this phenomenon is partially reversed by neutralizing cav-1 antibodies or using ganglia from cav-1 knockout mice. Our results show a novel paracrine mechanism used by the prostate cancer in PNI to increase their proliferative activity and decrease apoptosis. (Cancer Res 2006; 66(10): 5159-64)
Targeting Aurora Kinases for the Treatment of Prostate Cancer
Authors: Lee Edmund Chun Yu , Frolov Anna , Li Rile , Ayala Gustavo , Greenberg Norman M. 
Published: May 2006

Abstract
Inappropriate expression of the Aurora kinases can induce aberrant mitosis, centrosome irregularities, and chromosomal instability, which lead to anueploidy and cell transformation. Here, we report that Aurora-A and Aurora-B are highly expressed in primary human and mouse prostate cancers and prostate cancer cell lines. In clinical samples, levels of Aurora-A and Aurora-B were significantly elevated in prostatic intraepithelial neoplasia lesions and prostate tumors when compared with the non-neoplastic samples. Interestingly, expression of Aurora-A in non-neoplastic prostates correlated with seminal vesicle invasion (ρ = 0.275, P = 0.0169) and in prostate tumor with positive surgical margins (ρ = 0.265, P = 0.0161). In addition, nuclear expression of Aurora-B in prostatic intraepithelial neoplasia lesions correlated with clinical staging of the tumor (ρ = −0.4, P = 0.0474) whereas cytoplasmic expression in tumors correlated with seminal vesicle invasion (ρ = 0.282, P = 0.0098). Cell lines and primary tumors derived from the TRAMP model were also found to express high levels of Aurora-A and Aurora-B. When human PC3, LNCaP, and mouse C1A cells were treated with the potent Aurora kinase inhibitor VX680, which attenuates phosphorylation of histone H3, cancer cell survival was reduced. VX680 could further reduce cell viability &gt;2-fold when used in combination with the chemotherapy drug doxorubicin. Our findings support a functional relationship between Aurora kinase expression and prostate cancer and the application of small-molecule inhibitors in therapeutic modalities. (Cancer Res 2006; 66(10): 4996-5002)
Epidermal Growth Factor Induces Insulin Receptor Substrate-2 in Breast Cancer Cells via c-Jun NH2-Terminal Kinase/Activator Protein-1 Signaling to Regulate Cell Migration
Authors: Cui Xiaojiang , Kim Hyun-Jung , Kuiatse Isere , Kim Heetae , Brown Powel H. , Lee Adrian V. 
Published: May 2006

Abstract
The epidermal growth factor (EGF) and insulin-like growth factor (IGF) signaling pathways are critically involved in cancer development and progression. However, how these two signals cross-talk with each other to regulate cancer cell growth is not clearly understood. In this study, we found that EGF remarkably induced expression of major IGF signaling components, insulin receptor substrate (IRS)-1 and IRS-2, an effect that could be blocked by EGF receptor (EGFR) tyrosine kinase inhibitors. Although both extracellular signal-regulated kinase and c-Jun NH2-terminal kinase (JNK) signaling pathways were involved in the EGF up-regulation of IRS-1, the IRS-2 induction by EGF was specifically mediated by JNK signaling. Consistent with this, EGF increased IRS-2 promoter activity, which was associated with recruitment of activator protein-1 (AP-1) transcription factors and was inhibited by blocking AP-1 activity. Moreover, EGF treatment enhanced IGF-I and integrin engagement-elicited tyrosine phosphorylation of IRS and their downstream signaling, such as binding to phosphatidylinositol 3′-kinase regulatory subunit p85. Finally, repressing the induction of IRS-2 levels abolished the EGF enhancement of cell motility, suggesting that increased IRS-2 is essential for the EGF regulation of breast cancer cell migration. Taken together, our results reveal a novel mechanism of cross-talk between the EGF and IGF signaling pathways, which could have implications in therapeutic applications of targeting EGFR in tumors. Because AP-1 activity is involved in breast cancer progression, our work may also suggest IRS-2 as a useful marker for aggressive breast cancer. (Cancer Res 2006; 66(10): 5304-13)