bluuebunny/crossref_metadata_2025_split huggingface dataset:
Targeting and sequestration of truncated Pfs230 in an intraerythrocytic compartment during Plasmodium falciparum gametocytogenesis
Authors: Eksi Saliha , Stump Amy , Fanning Sarah L. , Shenouda Mary I. , Fujioka Hisashi , Williamson Kim C. 
Published: March 2003

SummaryFor malaria to be transmitted, the Plasmodium falciparum parasite must invade
an erythrocyte and undergo gametocytogenesis. When mature intraerythrocytic gametocytes
are taken up in a blood meal by a mosquito they emerge as gametes and, once fertilized,
continue to differentiate into infectious sporozoites. One of the major proteins
associated with the surface of the parasite during gamete differentiation is Pfs230,
a 360 kDa member of a family of P. falciparum proteins that contains a repeated
cysteine motif domain. To characterize the role of different regions of Pfs230, the
gene was disrupted by targeted integration and clones isolated that expressed distinct
sections of Pfs230. Independent clones D1.356 a and b express the first 452 amino
acids (aa) of Pfs230 and do not contain a cysteine motif domain, whereas clones D2.850
a and b express the first 950 aa, including the first cysteine motif domain. Although
both sets of clones undergo gametogenesis and produce morphologically normal gametes,
neither truncated Pfs230 is located on the surface of the gamete. In clones D1.356
a and b, the 452 aa Pfs230 is secreted into the parasitophorous vacuole and released
as a soluble protein when the parasite emerges from the erythrocyte as a gamete.
In marked contrast, the 950 aa form of Pfs230 expressed by clones D2.850 a and
b is sequestered in a novel tubular compartment in the erythrocyte cytoplasm. This
sexual‐stage tubular intraerythrocytic compartment (STIC) is not recognized by antibodies
specific for proteins associated with the parasitophorous vacuole membrane (Pfs16
or Exp‐1) or Maurer’s clefts (Pfsbp 1 or mAb LWL1) or intraerythrocytic asexual parasite proteins (PfEMP2 or HRP II).
Role of the extracytoplasmic‐function σ Factor σH in Mycobacterium tuberculosis global gene expression
Authors: Manganelli Riccardo , Voskuil Martin I. , Schoolnik Gary K. , Dubnau Eugenie , Gomez Manuel , Smith Issar 
Published: March 2003

SummaryLike other bacterial species, Mycobacterium tuberculosis has multiple sigma (σ) factors encoded in its genome. In previously published work, we and others have shown that mutations in some of these transcriptional activators render M. tuberculosis sensitive to various environmental stresses and, in some cases, cause attenuated virulence phenotypes. In this paper, we characterize a M. tuberculosis mutant lacking the ECF σ factor σH. This mutant was more sensitive than the wild type to heat shock and to various oxidative stresses, but did not show de‐creased ability to grow inside macrophages. Using quantitative reverse transcription‐PCR and microarray technology, we have started to define the σH regulon and its involvement in the global regulation of the response to heat shock and the thiol‐specific oxidizing agent diamide. We identified 48 genes whose expression increased after exposure of M. tuberculosis to diamide; out of these, 39 were not induced in the sigH mutant, showing their direct or indirect dependence on σH. Some of these genes encode proteins whose predicted function is related to thiol metabolism, such as thioredoxin, thioredoxin reductase and enzymes involved in cysteine and molybdopterine biosynthesis. Other genes under σH control encode transcriptional regulators such as sigB, sigE, and sigH itself.
Histone deacetylases in Trypanosoma brucei: two are essential and another is required for normal cell cycle progression
Authors: Ingram Alexandra K. , Horn David 
Published: March 2003

SummaryReversible protein acetylation is established as a modification of major regulatory significance. In particular, histone acetylation regulates access to genetic information in eukaryotes. For example, class I and class II histone deacetylases are regulatory components of corepressor complexes involved in cell cycle progression and differentiation. Here, we have investigated the function of such enzymes in Trypanosoma brucei, mono‐flagellated parasitic protozoa that branched very early from the eukaryotic lineage. Four T. brucei genes encoding histone deacetylase orthologues have been identified, cloned and characterized. The predicted deacetylases, DAC1‐4 are approximately 43, 61, 75 and 64 kDa respectively. They share significant similarity with mammalian and yeast class I (DAC1 and DAC2) and class II (DAC3 and DAC4) histone deacetylases, and all except DAC2 have the critical residues predicted to be required for deacetylase activity. In gene targeting experiments, DAC1 and DAC3 appear to be essential whereas DAC2 and DAC4 are not required for viability. Of the two mutant cell types, the dac4 mutant displays a delay in the G2/M phase of the cell cycle. Our results provide genetic validation of DAC1 and DAC3 as potential chemotherapy targets and demonstrate that T. brucei expresses at least three probable histone deacetylases with distinct function.
Cladosporium fulvum overcomes Cf‐2‐mediated resistance by producing truncated AVR2 elicitor proteins
Authors: Luderer Rianne , Takken Frank L. W. , Wit Pierre J. G. M. de , Joosten Matthieu H. A. J. 
Published: March 2003

SummaryThe Cf‐2 gene of tomato confers resistance to strains of the biotrophic pathogenic fungus Cladosporium fulvum carrying avirulence gene Avr2. To allow dissection of the biochemical mechanism of perception of AVR2 by Cf‐2, we set out to clone the Avr2 gene. Here, we report the functional cloning of Avr2 cDNA, based on the induction of a hypersensitive response (HR) by the encoded AVR2 protein in Cf2 tomato plants. Analysis of strains of C. fulvum that are virulent on Cf2 tomato lines revealed various independent frameshift mutations in the Avr2 open reading frame (ORF) and a point mutation resulting in a premature stop codon. All modifications result in the production of truncated AVR2 proteins. Interestingly, an additional modification involves the insertion of a LINE‐like element, Cfl1, in the Avr2 ORF. Cfl1 is the first LINE‐like element identified in C. fulvum and provides the first example of loss of avirulence of a plant pathogen caused by insertion of a retrotransposable element in an Avr gene. Rcr3 represents an additional plant protein that is specifically required for Cf‐2‐mediated resistance. Analysis of two different rcr3 mutant Cf2 tomato plants revealed that their ability to respond to AVR2 with a HR correlates with their degree of resistance to AVR2‐producing strains of C. fulvum. These data support a role for Rcr3 in the perception of AVR2 by Cf‐2.
Listeria monocytogenes bile salt hydrolase is a PrfA‐regulated virulence factor involved in the intestinal and hepatic phases of listeriosis
Authors: Dussurget Olivier , Cabanes Didier , Dehoux Pierre , Lecuit Marc ,   the European Listeria Genome Consortium, Buchrieser Carmen , Glaser Philippe , Cossart Pascale 
Published: March 2003

Summary Listeria monocytogenes
is a bacterial pathogen causing severe food‐borne infections in humans and animals. It can sense and adapt to a variety of harsh microenvironments outside as well as inside the host. Once ingested by a mammalian host, the bacterial pathogen reaches the intestinal lumen, where it encounters bile salts which, in addition to their role in digestion, have antimicrobial activity. Comparison of the
L. monocytogenes
and
Listeria innocua
genomes has revealed the presence of an
L. monocytogenes
‐specific putative gene encoding a bile salt hydrolase (BSH). Here, we show that the
bsh
gene encodes a functional intracellular enzyme in all pathogenic
Listeria
species. The
bsh
gene is positively regulated by PrfA, the transcriptional activator of known
L. monocytogenes
virulence genes. Moreover, BSH activity increases at low oxygen concentration. Deletion of
bsh
results in decreased resistance to bile
in vitro
, reduced bacterial faecal carriage after oral infection of the guinea‐pigs, reduced virulence and liver colonization after intravenous inoculation of mice. Taken together, these results demonstrate that BSH is a novel PrfA‐regulated
L. monocytogenes virulence factor involved in the intestinal and hepatic phases of listeriosis.
Genome sequence of Streptococcus agalactiae, a pathogen causing invasive neonatal disease
Authors: Glaser Philippe , Rusniok Christophe , Buchrieser Carmen , Chevalier Fabien , Frangeul Lionel , Msadek Tarek , Zouine Mohamed , Couvé Elisabeth , Lalioui Lila , Poyart Claire , Trieu‐Cuot Patrick , Kunst Frank 
Published: March 2003

Summary Streptococcus agalactiae
is a commensal bacterium colonizing the intestinal tract of a significant proportion of the human population. However, it is also a pathogen which is the leading cause of invasive infections in neonates and causes septicaemia, meningitis and pneumonia. We sequenced the genome of the serogroup III strain NEM316, responsible for a fatal case of septicaemia. The genome is 2 211 485 base pairs long and contains 2118 protein coding genes. Fifty‐five per cent of the predicted genes have an ortholog in the
Streptococcus pyogenes
genome, representing a conserved backbone between these two streptococci. Among the genes in
S. agalactiae
that lack an ortholog in
S. pyogenes
, 50% are clustered within 14 islands. These islands contain known and putative virulence genes, mostly encoding surface proteins as well as a number of genes related to mobile elements. Some of these islands could therefore be considered as pathogenicity islands. Compared with other pathogenic streptococci,
S. agalactiae shows the unique feature that pathogenicity islands may have an important role in virulence acquisition and in genetic diversity.
An Inv/Mxi‐Spa‐like type III protein secretion system in Burkholderia pseudomallei modulates intracellular behaviour of the pathogen
Authors: Stevens Mark P. , Wood Michael W. , Taylor Lowrie A. , Monaghan Paul , Hawes Pippa , Jones Philip W. , Wallis Timothy S. , Galyov Edouard E. 
Published: March 2003

Summary Burkholderia pseudomallei is the causative agent of melioidosis, a serious infectious disease of humans and animals that is endemic in subtropical areas. B. pseudomallei is a facultative intracellular pathogen that may invade and survive within eukaryotic cells for prolonged periods. After internalization, the bacteria escape from endocytic vacuoles into the cytoplasm of infected cells and form membrane protrusions by inducing actin polymerization at one pole. It is believed that survival within phagocytic cells and cell‐to‐cell spread via actin protrusions is required for full virulence. We have studied the role of a putative type III protein secretion apparatus (Bsa) in the interaction between B. pseudomallei and host cells. The Bsa system is very similar to the Inv/Mxi‐Spa type III secretion systems of Salmonella and Shigella. Moreover, B. pseudomallei encodes proteins that are very similar to Salmonella and Shigella Inv/Mxi‐Spa secreted proteins required for invasion, escape from endocytic vacuoles, intercellular spread and pathogenesis. Antibodies to putative Bsa‐secreted proteins were detected in convalescent serum from a melioidosis patient, suggesting that the system is functionally expressed in vivo. B. pseudomallei mutant strains lacking components of the Bsa secretion and translocation apparatus were constructed. The mutant strains exhibited reduced replication in J774.2 murine macrophage‐like cells, an inability to escape from endocytic vacuoles and a complete absence of formation of membrane protrusions and actin tails. These findings indicate that the Bsa type III secretion system plays an essential role in modulating the intracellular behaviour of B. pseudomallei.
A site‐specific recombinase (RinQ) is required to exert incompatibility towards the symbiotic plasmid of Rhizobium etli
Authors: Quintero Verónica , Cevallos Miguel A. , Dávila Guillermo 
Published: March 2003

SummaryThe replication/partition region of the symbiotic plasmid p42d of Rhizobium etli CE3 is characterized by the presence of the repABC operon. A recombinant plasmid containing this region is able to replicate in a R. etli derivative cured from p42d, with the same stability and copy number shown by the parental plasmid. However, when this construct is introduced into the wild‐type strain, instead of exerting incompatibility against the p42d, it forms a stable cointegrate with it. In this paper, we show that a site‐specific resolvase, and its action sites are essential factors to displace the symbiotic p42d. We propose a model for this novel incompatibility mechanism.
Molecular diversity of the genetic loci responsible for lipopolysaccharide core oligosaccharide assembly within the genus Salmonella
Authors: Kaniuk Natalia A. , Monteiro Mario A. , Parker Craig T. , Whitfield Chris 
Published: March 2003

SummaryThe waa locus on the chromosome of Salmonella enterica encodes enzymes involved in the assembly of the core oligosaccharide region of the lipopolysaccharide (LPS) molecule. To date, there are two known core structures in Salmonella, represented by serovars Typhimurium (subspecies I) and Arizonae (subspecies IIIA). The waa locus for serovar Typhimurium has been characterized. Here, the corresponding locus from serovar Arizonae is described, and the molecular basis for the distinctive structures is established. Eleven of the 13 open reading frames (ORFs) are shared by the two loci and encode conserved proteins of known function. Two polymorphic regions distinguish the waa loci. One involves the waaK gene, the product of which adds a terminal α‐1,2‐linked N‐acetylglucosamine residue that characterizes the serovar Typhimurium core oligosaccharide. There is an extensive internal deletion within waaK of serovar Arizonae. The serovar Arizonae locus contains a novel ORF (waaH) between the waaB and waaP genes. Structural analyses and in vitro glycosyltransferase assays identified WaaH as the UDP‐glucose:(glucosyl) LPS α‐1,2‐glucosyltransferase responsible for the addition of the characteristic terminal glucose residue found in serovar Arizonae. Isolates comprising the Salmonella Reference Collections, SARC (representing the eight subspecies of S. enterica) and SARB (representing subspecies I), were examined to assess the distribution of the waa locus polymorphic regions in natural populations. These comparative studies identified additional waa locus polymorphisms, shedding light on the genetic basis for diversity in the LPS core oligosaccharides of Salmonella isolates and identifying potential sources of further novel LPS structures.
Divergence and transcriptional analysis of the division cell wall (dcw) gene cluster in Neisseria spp.
Authors: Snyder Lori A. S. , Shafer William M. , Saunders Nigel J. 
Published: March 2003

SummaryThree of the 18 open reading frames in the division and cell wall synthesis cluster of the pathogenic Neisseria spp. are not present in the clusters of other bacterial species. The region containing two of these, dcaB and dcaC, displays interstrain and interspecies variability uncharacteristic of such clusters. 3′ of dcaB is a Correia repeat enclosed element (CREE), which is only present in some strains. It has been suggested that this CREE is a transcriptional terminator, although we demonstrate otherwise. A gearbox‐like promoter within this CREE is active in Escherichia coli but not in Neisseria meningitidis. There is an active promoter 5′ of dcaC, although its sequence is not conserved. The presence of similarly located promoters has not been demonstrated in other species. In Neisseria lactamica, this promoter involves another dcw‐associated CREE, the first demonstration of active promoter generation at the 5′ end of this common intergenic, apparently mobile, element. Upstream of this promoter is an inverted pair of neisserial uptake signal sequences, which are commonly considered to be transcriptional terminators. It has been proposed to terminate transcription in this location, although we have demonstrated transcript extending through this uptake signal sequence. dcaC contains a 108 bp tandem repeat, which is present in different copy numbers in the neisserial strains examined. This investigation reveals extensive sequence variation, disputes the presence of transcriptional terminators and identifies active internal promoters in this normally highly conserved cluster of essential genes, and addresses the transcriptional activity of two common neisserial intergenic components.
Regulation of Salmonella typhimurium lipopolysaccharide O antigen chain length is required for virulence; identification of FepE as a second Wzz
Authors: Murray Gerald L. , Attridge Stephen R. , Morona Renato 
Published: March 2003

SummaryWzz proteins regulate the degree of polymerization of the O antigen (Oag) subunits in lipopolysaccharide (LPS) biosynthesis. Although the pathogenic relevance of Oag is well recognized, the significance of Oag chain length regulation is not well defined. In this report, Salmonella typhimurium was shown to possess two functional wzz genes resulting in a bimodal Oag length distribution. In addition to the previously described wzzST that results in long (L) modal length LPS with 16–35 Oag repeat units (RUs), we now report that wzzfepE, a homologue of Escherichia coli fepE, is responsible for the production of very long (VL) modal length LPS Oag, estimated to contain> 100 Oag RUs. Analysis of a series of isogenic S. typhimurium C5 mutants found that the presence of either wzz gene (and hence either modal length) was sufficient for complement resistance and virulence in the mouse model of infection, suggesting a degree of redundancy in the role of these two wzz genes and their respective Oag modal lengths. In contrast, the wzzST/wzzfepE double mutant, with relatively short, random‐length Oag, displayed enhanced susceptibility to complement and was highly attenuated in the mouse. This clearly demonstrates the molecular genetic basis for the longer LPS Oag chains previously identified as the basis of complement resistance in Salmonella. The presence of wzzfepE homologues in the genomic sequences of strains of Escherichia coli, Shigella flexneri and multiple serovars of Salmonella suggests that bimodality of LPS Oag is a common phenomenon in the Enterobacteriaceae.
Stage‐specific gene expression of Candida albicans in human blood
Authors: Fradin Chantal , Kretschmar Marianne , Nichterlein Thomas , Gaillardin Claude , D’Enfert Christophe , Hube Bernhard 
Published: March 2003

SummaryThe pathogenic fungus Candida albicans commonly causes mucosal surface infections. In immunocompromised patients, C. albicans may penetrate into deeper tissue, enter the bloodstream and disseminate within the host causing life‐threatening systemic infections. In order to elucidate how C. albicans responds to the challenge of a blood environment, we analysed the transcription profile of C. albicans cells exposed to human blood using genomic arrays and a cDNA subtraction protocol. By combining data obtained with these two methods, we were able to identify unique sets of different fungal genes specifically expressed at different stages of this model that mimics bloodstream infections. By removing host cells and incubation in plasma, we were also able to identify several genes in which the expression level was significantly influenced by the presence of these cells. Differentially expressed genes included those that are involved in the general stress response, antioxidative response, glyoxylate cycle as well as putative virulence attributes. These data point to possible mechanisms by which C. albicans ensures survival in the hostile environment of the blood and how the fungus may escape the bloodstream as an essential step in its systemic dissemination.
Evidence of blood–brain barrier dysfunction in human cerebral malaria
Authors: Brown  , Hien  , Day  , Mai  , Chuong  , Chau  , Loc  , Phu  , Bethell  , Farrar  , Gatter  , White  , Turner  
Published: March 2003

Patients infected with the malaria parasite Plasmodium falciparum may develop a diffuse reversible encephalopathy, termed cerebral malaria. It is unclear how the intraerythrocytic parasite, which sequesters in the cerebral microvasculature but does not enter the brain parenchyma, induces this neurological syndrome. Adhesion of parasitized red blood cells in the brain microvasculature is mediated by specific receptors on the host endothelium, including intercellular adhesion molecule (ICAM)‐1, CD36 and CD31. Leucocyte binding to cerebral endothelial cells in culture induces intracellular signalling via ICAM‐1. The hypothesis that parasitized red blood cells binding to receptors on cerebral endothelial cells causes changes in the integrity of the blood–brain barrier was tested. Immunohistochemistry was used to examine the blood–brain barrier in human cerebral malaria, with antibodies to macrophage and endothelial activation markers, intercellular junction proteins, and plasma proteins. The distribution of the cell junction proteins occludin, vinculin and ZO‐1 were altered in cerebral malaria cases compared to controls. While fibrinogen was the only plasma protein detected in the perivascular space, there was widespread perivascular macrophage activation, suggesting that these cells had been exposed to plasma proteins. It was concluded that functional changes to the blood–brain barrier occur in cerebral malaria, possibly as a result of the binding of parasitized red blood cells to cerebral endothelial cells. These changes require further examination in vitro.
Familial British dementia (FBD): a cerebral amyloidosis with systemic amyloid deposition
Authors: Holton J. L. , Ghiso J. , Lashley T. , Ganguly M. , Strand K. , Rostagno A. , Plant G. , Frangione B. , Revesz T. 
Published: March 2003

Introduction:  FBD is an autosomal dominant disease with neuropathological similarities to Alzheimer's disease (AD) as it is characterized by amyloid angiopathy, parenchymal amyloid plaque deposition and neurofibrillary degeneration. FBD is associated with a stop codon mutation in the BRI2 gene encoding a type II transmembrane protein, BriPP. Mutation results in an extended precursor protein, ABriPP, from which a C‐terminal 34 amino acid peptide (ABri) is generated by furin‐like proteolytic cleavage and deposited as amyloid and preamyloid in the central nervous system. Despite the morphological parallels with AD the sequences of the amyloidogenic peptides, ABri in FBD and Aβ in AD, are completely different. We examined systemic tissues in FBD for ABri deposition.Materials and methods:  Immunohistochemistry using an ABri‐specific antibody, Ab338, counterstained with Thioflavin S and Ab338 immuno‐electron microscopy identified ABri deposits and determined whether these were amyloid or preamyloid in nature.Results:  Amyloid bearing blood vessels stained positively for ABri in myocardium, uterus, bladder, spleen, pancreas, lung and skeletal muscle. ABri was also identified in either amyloid or preamyloid conformation in the parenchyma of myocardium, adrenal, pancreas and skeletal muscle.Conclusion:  This study demonstrates that FBD is the first described cerebral amyloidosis with neurofibrillary pathology and dementia to be accompanied by systemic amyloid deposition.