bluuebunny/crossref_metadata_2025_split huggingface dataset:
CelTOS, a novel malarial protein that mediates transmission to mosquito and vertebrate hosts
Authors: Kariu Tohru , Ishino Tomoko , Yano Kazuhiko , Chinzei Yasuo , Yuda Masao 
Published: January 2006

SummaryThe malarial parasite has two hosts in its life cycle, a vertebrate and a mosquito. We report here that malarial invasion into these hosts is mediated by a protein, designated cell‐traversal protein for ookinetes and sporozoites (CelTOS), which is localized to micronemes that are organelles for parasite invasive motility. Targeted disruption of the CelTOS gene in Plasmodium berghei reduced parasite infectivity in the mosquito host approximately 200‐fold. The disruption also reduced the sporozoite infectivity in the liver and almost abolished its cell‐passage ability. Liver infectivity was restored in Kupffer cell‐depleted rats, indicating that CelTOS is necessary for sporozoite passage from the circulatory system to hepatocytes through the liver sinusoidal cell layer. Electron microscopic analysis revealed that celtos‐disrupted ookinetes invade the midgut epithelial cell by rupturing the cell membrane, but then fail to cross the cell, indicating that CelTOS is necessary for migration through the cytoplasm. These results suggest that conserved cell‐passage mechanisms are used by both sporozoites and ookinetes to breach host cellular barriers. Elucidation of these mechanisms might lead to novel antimalarial strategies to block parasite's transmission.
The ISWI and CHD1 chromatin remodelling activities influence ADH2 expression and chromatin organization
Authors: Xella Barbara , Goding Colin , Agricola Eleonora , Di Mauro Ernesto , Caserta Micaela 
Published: January 2006

SummaryNucleosome remodelling complexes play a key role in gene activation in response to environmental changes by driving promoter chromatin to reach an accessible configuration. They also mediate genome‐wide chromatin organization, although their role in processes other than activation‐related chromatin remodelling are poorly understood. The Saccharomyces cerevisiae ADH2 gene represents an excellent model for understanding the role of chromatin structure and remodelling in gene regulation. Following glucose depletion, highly positioned promoter nucleosomes are destabilized leading to strictly regulated kinetics of transcriptional activation. Nevertheless, no chromatin remodelling activities responsible for establishing or remodelling ADH2 chromatin structure have been identified to date. Here we show that the absence of the Isw1 and Chd1 ATP‐dependent chromatin remodelling activities delays the maximal expression of ADH2 without impairing the chromatin remodelling that occurs upon activation. Instead, a destabilized chromatin structure on the ADH2 coding and termination region is observed in the absence of Isw1 or Chd1 in repressing conditions. The specific Isw1 complex involved in this nucleosome repositioning is Isw1b because the deletion of Ioc2 and Ioc4, but not of Ioc3, causes the same phenotype as the deletion of Isw1. Moreover, the lack of Chd1 combined with the absence of Isw1 and Isw2 impairs nucleosome spacing along the ADH2 gene, and genome‐wide in S. cerevisiae. Thus, the ISWI and Chd1 remodelling factors are not only involved in transcription‐related chromatin remodelling, but also are required to maintain a specific chromatin configuration across the yeast genome.
Mycobacterium tuberculosis prcBA genes encode a gated proteasome with broad oligopeptide specificity
Authors: Lin Gang , Hu Guiqing , Tsu Christopher , Kunes Yune Z. , Li Huilin , Dick Lawrence , Parsons Thomas , Li Ping , Chen Zhiqiang , Zwickl Peter , Weich Nadine , Nathan Carl 
Published: January 2006

SummaryGenes predicted to be associated with the putative proteasome of Mycobacterium tuberculosis (Mtb) play a critical role in defence of the bacillus against nitrosative stress. However, proteasomes are uncommon in eubacteria and it remains to be established whether Mtb's prcBA genes in fact encode a proteasome. We found that coexpression of recombinant PrcB and PrcA in Escherichia coli over a prolonged period at 37°C allowed formation of an α7β7β7α7, 750 kDa cylindrical stack of four rings in which all 14 β‐subunits were proteolytically processed to expose the active site threonine. In contrast to another Actinomycete, Rhodococcus erythropolis, Mtb's β‐chain propeptide was not required for particle assembly. Peptidolytic activity of the 750 kDa particle towards a hydrophobic oligopeptide was nearly two orders of magnitude less than that of the Rhodococcus 20S proteasome, and unlike eukaryotic and archaeal proteasomes, activity of the Mtb 750 kDa particle could not be stimulated by SDS, Mg2+ or Ca2+. Electron microscopy revealed what appeared to be obstructed α‐rings in the Mtb 750 kDa particle. Deletion of the N‐terminal octapeptide from Mtb's α‐chain led to disappearance of the apparent obstruction and a marked increase of peptidolytic activity. Unlike proteasomes isolated from other Actinomycetes, the open‐gate Mtb mutant 750 kDa particle cleaved oligopeptides not only after hydrophobic residues but also after basic, acidic and small, neutral amino acids. Thus, Mtb encodes a broadly active, gated proteasome that may work in concert with an endogenous activator.
CRZ1, a target of the calcineurin pathway in Candida albicans
Authors: Karababa Mahir , Valentino Emilio , Pardini Giacomo , Coste Alix T. , Bille Jacques , Sanglard Dominique 
Published: January 2006

SummaryCalcineurin is a major player in calcium‐dependent signal transduction pathways of eukaryotes. Calcineurin acts on transcription factors (e.g. CRZ1 in Saccharomyces cerevisiae) and governs the expression of genes in a species‐dependent fashion. In Candida albicans, the calcineurin pathway is involved in tolerance to antifungal agents, cation homeostasis and virulence. However, the components of the calcineurin pathway are still poorly investigated in this yeast species. Taking S. cerevisiae as a model to reconstitute this pathway, two CRZ1‐like genes, CRZ1 and CRZ2 (for calcineurin‐responsive zinc finger 1 and 2 genes), were found with C2H2 zinc finger domains. Only CRZ1 was able to restore the calcium hypersusceptibility of a S. cerevisiae crz1Δ mutant and to mediate calcium‐dependent gene expression in this yeast species. Several experiments showed that CRZ1 was dependent on calcineurin in C. albicans: (i) phenotypic analysis of a crz1Δ/Δ mutant showed impaired growth as compared with the wild type in the presence of cations (Ca2+, Mn2+) as does a mutant lacking calcineurin subunit A (cnaΔ/Δ) and (ii) a green fluorescent protein (GFP)–Crz1p fusion protein showed a calcium‐ and calcineurin‐dependent nuclear localization. To further analyse the relationship between calcineurin and CRZ1, a comprehensive analysis of calcineurin/Crz1p‐dependent gene expression following addition of Ca2+ (200 mM) was performed. Among the expression of 264 genes altered by at least twofold, the upregulation of 60 genes was dependent on both calcineurin and CRZ1. Interestingly, a motif [5′‐G(C/T)GGT‐3′] with similarity to the target sequence of Crz1p (GNGGCG/TCA) from S. cerevisiae was identified as a putative regulatory sequence in the upstream regions of these calcineurin/Crz1p‐dependent genes. However, additional experiments showed that calcineurin may have other targets in addition to CRZ1. First, CRZ1 was not involved in tolerance to antifungal agents (fluconazole, terbinafine) on the opposite to calcineurin. Second, CRZ1 was only moderately influencing virulence in a mice model of infection which is in sharp contrast to the strong avirulence of cnaΔ/Δ mutant in the same animal model. Even though this work establishes CRZ1 as a calcineurin target, further studies are needed to identify other calcineurin‐dependent elements in C. albicans.
Inactivation of the fibronectin‐binding adhesin gene bbk32 significantly attenuates the infectivity potential of Borrelia burgdorferi
Authors: Seshu J. , Esteve‐Gassent M. Dolores , Labandeira‐Rey Maria , Kim Jung Hwa , Trzeciakowski Jerome P. , Höök Magnus , Skare Jonathan T. 
Published: January 2006

SummaryBorrelia burgdorferi, the aetiological agent of Lyme disease, utilizes multiple adhesins to interact with both the arthropod vector and mammalian hosts it colonizes. One such adhesive molecule is a surface‐exposed fibronectin‐binding lipoprotein, designated BBK32. Previous characterization of BBK32‐mediated fibronectin binding has been limited to biochemical analyses due to the difficulty in mutagenizing infectious isolates of B. burgdorferi. Here we report an alternative method to inactivate bbk32 via allelic exchange through use of a low‐passage variant of B. burgdorferi strain B31 that is more readily transformed. The resulting mutant does not synthesize BBK32, exhibits reduced fibronectin binding in solid phase assays and manifests decreased interactions with mouse fibroblast cells relative to both the infectious parent and genetic complement. Furthermore, the bbk32 knockout was significantly attenuated in the murine model of Lyme disease, whereas a genetically complemented control was not, indicating that BBK32 is necessary for maximal B. burgdorferi infection in the mouse. To our knowledge this is the first mutational analysis of a surface exposed, functional borrelial lipoprotein adhesin whose activity is associated with the mammalian host environment. By analogy with other pathogens that utilize fibronectin binding as an important virulence determinant, the borrelial fibronectin–BBK32 interaction is likely to be important in B. burgdorferi‐specific pathogenic mechanisms, particularly in the context of dissemination, secondary colonization and/or persistence.
Ammonium permease‐based sensing mechanism for rapid ammonium activation of the protein kinase A pathway in yeast
Authors: Van Nuland An , Vandormael Patrick , Donaton Monica , Alenquer Marta , Lourenço Artur , Quintino Edgar , Versele Matthias , Thevelein Johan M. 
Published: January 2006

SummaryIn the yeast Saccharomyces cerevisiae starvation for nitrogen on a glucose‐containing medium causes entrance into G0 and downregulation of all targets of the PKA pathway. Re‐addition of a nitrogen source in the presence of glucose causes rapid activation of trehalase and other PKA targets. Trehalase activation upon ammonium re‐supplementation is dependent on PKA activity, but not on its regulatory subunit nor is it associated with an increase in cAMP. In nitrogen‐starved cells, ammonium transport and activation of trehalase are most active in strains expressing either the Mep2 or Mep1 ammonium permease, as opposed to Mep3. The non‐metabolizable ammonium analogue, methylamine, also triggers activation of trehalase when transported by Mep2 but not when taken up by diffusion. Inhibition of ammonium incorporation into metabolism did not prevent signalling. Extensive site‐directed mutagenesis of Mep2 showed that transport and signalling were generally affected in a similar way, although they could be separated partially by specific mutations. Our results suggest an ammonium permease‐based sensing mechanism for rapid activation of the PKA pathway. Mutagenesis of Asn246 to Ala in Mep2 abolished transport and signalling with methylamine but had no effect with ammonium. The plant AtAmt1;1, AtAmt1;2, AtAmt1;3 and AtAmt2 ammonium transporters sustained transport and trehalase activation to different extents. Specific mutations in Mep2 affected the activation of trehalase differently from induction of pseudohyphal differentiation. We also show that Mep permease involvement in PKA control is different from their role in haploid invasive growth, in which Mep1 sustains and Mep2 inhibits, in a way independent of the ammonium level in the medium.
GTP drives myosin light chain 1 interaction with the class V myosin Myo2 IQ motifs via a Sec2 RabGEF‐mediated pathway
Authors: Bielli Pamela , Casavola Elena Caroli , Biroccio Antonino , Urbani Andrea , Ragnini‐Wilson Antonella 
Published: January 2006

SummaryThe yeast myosin light chain 1 (Mlc1p) belongs to a branch of the calmodulin superfamily and is essential for vesicle delivery at the mother‐bud neck during cytokinesis due to is ability to bind to the IQ motifs of the class V myosin Myo2p. While calcium binding to calmodulin promotes binding/release from the MyoV IQ motifs, Mlc1p is unable to bind calcium and the mechanism of its interaction with target motifs has not been clarified. The presence of Mlc1p in a complex with the Rab/Ypt Sec4p and with Myo2p suggests a role for Mlc1p in regulating Myo2p cargo binding/release by responding to the activation of Rab/Ypt proteins. Here we show that GTP or GTPγS potently stimulate Mlc1p interaction with Myo2p IQ motifs. The C‐terminus of the Rab/Ypt GEF Sec2p, but not Sec4p activation, is essential for this interaction. Interestingly, overexpression of constitutively activated Ypt32p, a Rab/Ypt protein that acts upstream of Sec4p, stimulates Mlc1p/Myo2p interaction similarly to GTP although a block of Ypt32 GTP binding does not completely abolish the GTP‐mediated Mlc1p/Myo2p interaction. We propose that Mlc1p/Myo2p interaction is stimulated by a signal that requires Sec2p and activation of Ypt32p.
A new protein superfamily includes two novel 3‐methyladenine DNA glycosylases from Bacillus cereus, AlkC and AlkD
Authors: Alseth Ingrun , Rognes Torbjørn , Lindbäck Toril , Solberg Inger , Robertsen Kristin , Kristiansen Knut Ivan , Mainieri Davide , Lillehagen Lucy , Kolstø Anne‐Brit , Bjørås Magnar 
Published: January 2006

SummarySoil bacteria are heavily exposed to environmental methylating agents such as methylchloride and may have special requirements for repair of alkylation damage on DNA. We have used functional complementation of an Escherichia coli tag alkA mutant to screen for 3‐methyladenine DNA glycosylase genes in genomic libraries of the soil bacterium Bacillus cereus. Three genes were recovered: alkC, alkD and alkE. The amino acid sequence of AlkE is homologous to the E. coli AlkA sequence. AlkC and AlkD represent novel proteins without sequence similarity to any protein of known function. However, iterative and indirect sequence similarity searches revealed that AlkC and AlkD are distant homologues of each other within a new protein superfamily that is ubiquitous in the prokaryotic kingdom. Homologues of AlkC and AlkD were also identified in the amoebas Entamoeba histolytica and Dictyostelium discoideum, but no other eukaryotic counterparts of the superfamily were found. The alkC and alkD genes were expressed in E. coli and the proteins were purified to homogeneity. Both proteins were found to be specific for removal of N‐alkylated bases, and showed no activity on oxidized or deaminated base lesions in DNA. B. cereus AlkC and AlkD thus define novel families of alkylbase DNA glycosylases within a new protein superfamily.
Replication‐associated gene dosage effects shape the genomes of fast‐growing bacteria but only for transcription and translation genes
Authors: Couturier Etienne , Rocha Eduardo P. C. 
Published: January 2006

SummaryThe bidirectional replication of bacterial genomes leads to transient gene dosage effects. Here, we show that such effects shape the chromosome organisation of fast‐growing bacteria and that they correlate strongly with maximal growth rate. Surprisingly the predicted maximal number of replication rounds shows little if any phylogenetic inertia, suggesting that it is a very labile trait. Yet, a combination of theoretical and statistical analyses predicts that dozens of replication forks may be simultaneously present in the cells of certain species. This suggests a strikingly efficient management of the replication apparatus, of replication fork arrests and of chromosome segregation in such cells. Gene dosage effects strongly constrain the position of genes involved in translation and transcription, but not other highly expressed genes. The relative proximity of the former genes to the origin of replication follows the regulatory dependencies observed under exponential growth, as the bias is stronger for RNA polymerase, then rDNA, then ribosomal proteins and tDNA. Within tDNAs we find that only the positions of the previously proposed ‘ubiquitous’ tRNA, which translate the most frequent codons in highly expressed genes, show strong signs of selection for gene dosage effects. Finally, we provide evidence for selection acting upon genome organisation to take advantage of gene dosage effects by identifying a positive correlation between genome stability and the number of simultaneous replication rounds. We also show that gene dosage effects can explain the over‐representation of highly expressed genes in the largest replichore of genomes containing more than one chromosome. Together, these results demonstrate that replication‐associated gene dosage is an important determinant of chromosome organisation and dynamics, especially among fast‐growing bacteria.
A C‐terminal translocation signal is necessary, but not sufficient for type IV secretion of the Helicobacter pylori CagA protein
Authors: Hohlfeld Sabine , Pattis Isabelle , Püls Jürgen , Plano Gregory V. , Haas Rainer , Fischer Wolfgang 
Published: January 2006

SummaryType IV secretion systems are increasingly recognized as important virulence determinants of Gram‐negative bacterial pathogens. While the examination of several type IV‐secreted proteins suggested that their secretion depends on C‐terminal signals, the nature of these signals and their conservation among different systems remain unclear. Here, we have characterized the secretion signal of the Helicobacter pylori CagA protein, which is translocated by the Cag type IV secretion apparatus into eucaryotic cells. The production of fusion proteins of CagA and green fluorescent protein (GFP) did not result in translocation of GFP to epithelial cells, but a fusion of GFP with the CagA C‐terminus exerted a dominant‐negative effect upon wild‐type CagA translocation. We show that CagA translocation depends on the presence of its 20 C‐terminal amino acids, containing an array of positively charged residues. Interestingly, these positive charges are neither necessary nor sufficient for CagA translocation, but replacing the C‐terminal region of CagA with that of other type IV‐secreted proteins reconstitutes CagA translocation competence. Using a novel type IV translocation assay with a phosphorylatable peptide tag, we show that removal of the N‐terminal part of the CagA protein renders the protein translocation‐incompetent as well. Thus, the Cag type IV secretion system seems to diverge from other systems not only with respect to its composition and architecture, but also in terms of substrate recognition and transport.
Tinea capitis in eastern Nepal
Authors: Jha Bibeka Nand , Garg Vijay Kumar , Agrawal Sudha , Khanal Basudha , Agarwalla Arun 
Published: January 2006

AbstractBackground  Tinea capitis is an increasing public health concern throughout the world. The clinical types and etiological agents vary from time to time and place to place. This study was undertaken to identify the etiological agents and to determine the clinico‐etiological correlation of tinea capitis in eastern Nepal.Methods  Sixty‐nine clinically diagnosed cases of tinea capitis were enrolled in this study. Hair roots and skin scrapings were collected from each patient and subjected to microscopy and culture for identification of fungal hyphae and spores.Results  Tinea capitis accounted for 4.6% of all dermatophyte infections: 68.1% occurred in patients below the age of 11 years with a male to female ratio of 1 : 1.9. “Gray patch” was the most common clinical type (52.2%), followed by “black dot” (17.4%), seborrhoeic dermatitis (13%), alopecia areata (11.6%) and pustular (4.3%). Direct microscopy of hair was positive in 62.3% of patients. Culture positivity was found in 56.7% of patients. Common isolated organisms were Trichophyton violaceum (48.71%), T. mentagrophytes (15.38%), T. tonsurans (12.82%), Microsporum canis (7.69%), T. rubrum and M. gypseum (5.12% each), and M. audouinii and M. nanum (2.56% each).Conclusions  Trichophyton violaceum was the most common pathogen of tinea capitis. The clinical manifestations were variable and “gray patch” was the most common clinical presentation in this part of the world.
A new gastrointestinal finding in Proteus syndrome: report of a case of multiple colonic hemangiomas
Authors: Farajzadeh Saideh , Zahedi Mohammad Javad , Moghaddam Sodaif Darvish 
Published: January 2006

A patient with Proteus syndrome presented with lower gastrointestinal bleeding due to multiple colonic hemangiomas, a finding which has not been described previously in this syndrome. The patient was a 20‐year‐old man with features fulfilling the diagnostic criteria for Proteus syndrome. He fulfilled both general criteria (mosaic distribution of the lesions, progressive course and sporadic occurrence) and specific criteria (including epidermal nevus, disproportionate overgrowth of limbs and vascular malformations). Fiberoptic colonoscopy revealed multiple hemangiomas, 0.5–1 cm in diameter, on the left side of the colon. Some gastrointestinal complications have been reported in patients with Proteus syndrome, including rectal polyps, colonic lipomatosis, atrophy of the intestinal villi and intestinal affection with fatty wall thickening but, as far as we are aware, colonic hemangiomas have not previously been reported in this syndrome.
Epidemiology of pemphigus in south‐western Iran: A 10‐year retrospective study (1991–2000)
Authors: Salmanpour R. , Shahkar H. , Namazi M. R. , Rahman‐Shenas M. R. 
Published: January 2006

AbstractBackground  Pemphigus is a disease demonstrating an uneven geographic distribution. This is the first epidemiologic study of pemphigus in Iran.Methods  Data were collected from the files of all newly registered patients with pemphigus at the sole dermatologic referral center for south‐western Iran located in the city of Shiraz, during the period 1991–2000. The data were analyzed with regard to age, sex, subtypes of pemphigus, clinical presentation, and season of onset.Results  The results showed that the mean incidence of the disease for the overall population in Shiraz was 0.67/105/year. The male to female ratio was 1 : 1.33. The mean age at onset of the disease was 38 years (range, 12–93 years). The disease was most common in the third to fifth decades (62.1% of the overall patients). Pemphigus vulgaris was the most commonly encountered type, followed by pemphigus foliaceus (87.7% and 9%, respectively). The first manifestations of the illness most often occurred during winter (30.8% of the patients).Conclusions  The results reveal a high incidence of pemphigus vulgaris in south‐western Iran compared with that encountered in other countries. Our patients also had a relatively young age at onset and a female predominance.