bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aspergillus nidulans HOG pathway is activated only by two‐component signalling pathway in response to osmotic stress
Authors: Furukawa Kentaro , Hoshi Yukiko , Maeda Tatsuya , Nakajima Tasuku , Abe Keietsu 
Published: May 2005

SummaryGenome sequencing analyses revealed that Aspergillus nidulans has orthologous genes to all those of the high‐osmolarity glycerol (HOG) response mitogen‐activated protein kinase (MAPK) pathway of Saccharomyces cerevisiae. A. nidulans mutant strains lacking sskA, sskB, pbsB, or hogA, encoding proteins orthologous to the yeast Ssk1p response regulator, Ssk2p/Ssk22p MAPKKKs, Pbs2p MAPKK and Hog1p MAPK, respectively, showed growth inhibition under high osmolarity, and HogA MAPK in these mutants was not phosphorylated under osmotic or oxidative stress. Thus, activation of the A. nidulans HOG (AnHOG) pathway depends solely on the two‐component signalling system, and MAPKK activation mechanisms in the AnHOG pathway differ from those in the yeast HOG pathway, where Pbs2p is activated by two branches, Sln1p and Sho1p. Expression of pbsB complemented the high‐osmolarity sensitivity of yeast pbs2Δ, and the complementation depended on Ssk2p/Ssk22p, but not on Sho1p. Pbs2p requires its Pro‐rich motif for binding to the Src‐homology3 (SH3) domain of Sho1p, but PbsB lacks a typical Pro‐rich motif. However, a PbsB mutant (PbsB(Pro)) with the yeast Pro‐rich motif was activated by the Sho1p branch in yeast. In contrast, HogA in sskAΔ expressing PbsB(Pro) was not phosphorylated under osmotic stress, suggesting that A. nidulans ShoA, orthologous to yeast Sho1p, is not involved in osmoresponsive activation of the AnHOG pathway. We also found that besides HogA, PbsB can activate another Hog1p MAPK orthologue, MpkC, in A. nidulans, although mpkC is dispensable in osmoadaptation. In this study, we discuss the differences between the AnHOG and the yeast HOG pathways.
The Bacillus subtilis ydcDE operon encodes an endoribonuclease of the MazF/PemK family and its inhibitor
Authors: Pellegrini Olivier , Mathy Nathalie , Gogos Arhonda , Shapiro Lawrence , Condon Ciarán 
Published: May 2005

SummaryOperons encoding stable toxins and their labile antidote are widespread in prokaryotes and play important roles in plasmid partitioning and cellular responses to stress. One such family of toxins MazF/ChpAK/PemK encodes an endoribonuclease that inactivates cellular mRNAs by cleaving them at specific, but frequently occurring sites. Here we show that the Bacillus subtilis ydcE gene encodes a member of this family of RNases, which we have called EndoA. Overexpression of EndoA is toxic for bacterial cell growth and this toxicity is reversed by coexpression of the gene immediately upstream, ydcD. Furthermore, YdcD inhibits EndoA activity directly in vitro. EndoA has similar cleavage specificity to MazF and PemK and yields cleavage products with 3′‐phosphate and 5′‐hydroxyl groups, typical of EDTA‐resistant degradative RNases. This is the first example of an antitoxin–toxin system in B. subtilis.
Mycobacterium avium 104 deleted of the methyltransferase D gene by allelic replacement lacks serotype‐specific glycopeptidolipids and shows attenuated virulence in mice
Authors: Krzywinska Elzbieta , Bhatnagar Sanchita , Sweet Lindsay , Chatterjee Delphi , Schorey Jeffrey S. 
Published: May 2005

Summary Mycobacterium avium is a major opportunistic pathogen of AIDS patients in the United States. The understanding of M. avium pathogenesis has been hampered by the inability to create gene knockouts by homologous recombination, an important mechanism for defining and characterizing virulence factors. In this study a functional methyltransferase D (mtfD) gene was deleted by allelic replacement in the M. avium strain 104. Methyltransferase D is involved in the methylation of glycopeptidolipids (GPLs); highly antigenic glycolipids found in copious amounts on the M. avium cell surface. Interestingly, the loss of mtfD resulted in M. avium 104 containing only the non‐serotype specific GPL. Results also suggest that the mtfD encodes for a 3‐O‐methyltransferase. The absence of significant amounts of any serotype‐specific GPLs as a consequence of mtfD deletion indicates that the synthesis of the core 3,4‐di‐O‐methyl rhamnose is a prerequisite for synthesis of the serotype‐specific GPLs. Macrophages infected with the mtfD mutant show elevated production of tumour necrosis factor‐α (TNF‐α) and RANTES compared to control infections. In addition, the M. avium 104 mtfD mutant exhibits decreased ability to survive/proliferate in mouse liver and lung compared to wild‐type 104, as assessed by bacterial counts. Importantly, the mtfD mutant complemented with a wild‐type mtfD gene maintained an infection level similar to wild‐type. These experiments demonstrate that the loss of mtfD results in a M. avium 104 strain, which preferentially activates macrophages in vitro and shows attenuated virulence in mice. Together our data support a role for GPLs in M. avium pathogenesis.
A member of the cAMP receptor protein family of transcription regulators in Mycobacterium tuberculosis is required for virulence in mice and controls transcription of the rpfA gene coding for a resuscitation promoting factor
Authors: Rickman Lisa , Scott Colin , Hunt Debbie M. , Hutchinson Thomas , Menéndez M. Carmen , Whalan Rachael , Hinds Jason , Colston M. Joseph , Green Jeffrey , Buxton Roger S. 
Published: May 2005

SummaryDeletion of gene Rv3676 in Mycobacterium tuberculosis coding for a transcription factor belonging to the cAMP receptor protein (CRP) family caused growth defects in laboratory medium, in bone marrow‐derived macrophages and in a mouse model of tuberculosis. Transcript profiling of M. tuberculosis grown in vitro identified 16 genes with significantly altered expression in the mutant compared with the wild type. Analysis of the DNA sequences upstream of the corresponding open reading frames revealed that 12 possessed sequences related to a consensus CRP binding site that could represent the sites of action of Rv3676. These included rpfA, lprQ, whiB1 and ahpC among genes with enhanced expression in the wild type, and Rv3616c‐Rv3613c, Rv0188 and lipQ among genes exhibiting enhanced expression in the mutant. The activity of an rpfA::lacZ promoter fusion was lowered in the Rv3676 mutant and by mutation of the predicted Rv3676 binding site. Moreover, the product of Rv3676 (isolated as a TrxA fusion protein) interacted specifically with the rpfA promoter, and binding was inhibited by mutation of the Rv3676 site. Although Rv3676 retains four of the six amino acid residues that bind cAMP in Escherichia coli CRP addition of cAMP did not enhance Rv3676 binding at the rpfA promoter in vitro. In summary, it has been shown that Rv3676 is a direct regulator of rpfA expression, and because rpfA codes for a resuscitation promoting factor this may implicate Rv3676 in reactivation of dormant M. tuberculosis infections.
Switching aconitase B between catalytic and regulatory modes involves iron‐dependent dimer formation
Authors: Tang Yue , Guest John R. , Artymiuk Peter J. , Green Jeffrey 
Published: May 2005

SummaryIn addition to being the major citric acid cycle aconitase in Escherichia coli the aconitase B protein (AcnB) is also a post‐transcriptional regulator of gene expression. The AcnB proteins represent a distinct branch of the aconitase superfamily that possess a HEAT‐like domain (domain 5). The HEAT domains of other proteins are implicated in protein:protein interactions. Gel filtration analysis has now shown that cell‐free extracts contain high‐molecular‐weight species of AcnB. Furthermore, in vitro and in vivo protein interaction experiments have shown that AcnB forms homodimers. Addition of the iron chelator bipyridyl to cultures inhibited the dimer‐dependent readout from an AcnB bacterial two‐hybrid system. A similar response was observed with a catalytically inactive AcnB variant, AcnB(C769S), suggesting that the monomer–dimer transition is not mediated by the state of the AcnB iron–sulphur cluster. The iron‐responsive interacting unit was accordingly traced to the N‐terminal region (domains 4 and 5) of the AcnB protein, and not to domain 3 that houses the iron–sulphur cluster. Thus, it was shown that a polypeptide containing AcnB N‐terminal domains 5 and 4 (AcnB5‐4) interacts with a second AcnB5‐4 to form a homodimer. AcnB has recently been shown to initiate a regulatory cascade controlling flagella biosynthesis in Salmonella enterica by binding to the ftsH transcript and inhibiting the synthesis of the FtsH protease. A plasmid encoding AcnB5‐4 complemented the flagella‐deficient phenotype of a S. enterica acnB mutant, and the isolated AcnB5‐4 polypeptide specifically recognized and bound to the ftsH transcript. Thus, the N‐terminal region of AcnB is necessary and sufficient for promoting the formation of AcnB dimers and also for AcnB binding to target mRNA. Furthermore, the relative effects of iron on these processes provide a simple iron‐mediated dimerization mechanism for switching the AcnB protein between catalytic and regulatory roles.
The two‐component response regulator PprB modulates quorum‐sensing signal production and global gene expression in Pseudomonas aeruginosa
Authors: Dong Yi‐Hu , Zhang Xi‐Fen , Soo Hui‐Meng Linda , Greenberg Everett P. , Zhang Lian‐Hui 
Published: May 2005

SummaryThe response regulator PprB and its cognate sensor PprA were recently reported as a two‐component regulatory system that controls membrane permeability and antibiotic sensitivity of Pseudomonas aeruginosa. We found that a Tn5 insertion mutation in pprB caused a drastic reduction in virulence factor production and cell motility. A transcriptome analysis revealed that 175 genes were regulated by PprB. Among the 113 PprB‐activated genes, 85.5% are known to be activated by N‐3‐oxo‐dodecanoyl‐homoserine lactone (OdDHL) and N‐butanoyl‐homoserine lactone (BHL). In particular, the expression of lasI, rhlI and rhlR, which encode key components of the las and rhl quorum‐sensing (QS) systems, were significantly decreased in the pprB mutant. These data suggest that PprB might regulate QS signal production. Measurement of OdDHL and BHL in cultures of the mutant sustained this hypothesis. By using various OdDHL‐ or BHL‐responsive QS reporter systems, including lasB–lacZ, lasI–lacZ and rsaL–lacZ, we found that the mutation in pprB resulted in a large decrease in the sensitivity of P. aeruginosa to exogenous OdDHL. However, there was no difference in sensitivity to BHL. Further analysis showed that the OdDHL influx was significantly reduced in the pprB mutant. We conclude that PprB is a novel QS modulator that positively regulates N‐acylhomoserine lactone production probably by affecting the OdDHL signal influx and thereby influences global expression of the QS‐dependent genes.
Modulating factors for the Pkn4 kinase cascade in regulating 6‐phosphofructokinase in Myxococcus xanthus
Authors: Nariya Hirofumi , Inouye Sumiko 
Published: May 2005

Summary Myxococcus xanthus, a Gram‐negative developmental bacterium, contains a large number of protein Ser/Thr kinases (PSTKs). Among these PSTKs, Pkn4 has been shown to be 6‐phosphofructokinase (PFK) kinase. PFK associates with the regulatory domain of Pkn4 (Pkn4RD) and is activated by Pkn4‐mediated phosphorylation. The activation of PFK is required to consume glycogen accumulated during early development and is essential for efficient sporulation. Using the yeast two‐hybrid screen, we identified three new factors, MkapA, MkapB and MkapC, that interact with Pkn4 and each contains well‐known protein–protein interaction domains. MkapB contains eight tandem repeats of the TPR (tetratrico peptide repeat) domain and its interaction with Pkn4RD was phosphorylation‐dependent. MkapB remained associated with Pkn4RD. As a result, Pkn4 did not interact with PFK and its activation was inhibited. While deletion of the pfk‐pkn4 operon did not inhibit fruiting body formation, the spore yield was low. In contrast, a mkapB deletion mutant exhibited a 24 h delay in fruiting body formation, accumulated less glycogen in the stationary phase and gave rise to 3.2% spore formation as opposed to 100% attained with DZF1. In addition to Pkn4, MkapA associated with other membrane‐associated PSTKs, Pkn1, Pkn2, Pkn8 and Pkn9, while MkapB associated with Pkn8 and Pkn9, and MkapC with Pkn8. These results indicate that there are complex PSTK networks in M. xanthus that share common modulating factors.
CPCR1, but not its interacting transcription factor AcFKH1, controls fungal arthrospore formation in Acremonium chrysogenum
Authors: Hoff Birgit , Schmitt Esther K. , Kück Ulrich 
Published: May 2005

SummaryFungal morphogenesis and secondary metabolism are frequently associated; however, the molecular determinants connecting both processes remain largely undefined. Here we demonstrate that CPCR1 (cephalosporin C regulator 1 from Acremonium chrysogenum), a member of the winged helix/regulator factor X (RFX) transcription factor family that regulates cephalosporin C biosynthesis, also controls morphological development in the β‐lactam producer A. chrysogenum. The use of a disruption strain, multicopy strains as well as several recombinant control strains revealed that CPCR1 is required for hyphal fragmentation, and thus the formation of arthrospores. In a ΔcpcR1 disruption strain that exhibits only hyphal growth, the wild‐type cpcR1 gene was able to restore arthrospore formation; a phenomenon not observed for ΔcpcR1 derivatives or non‐related genes. The intracellular expression of cpcR1, and control genes (pcbC, egfp) was determined by in vivo monitoring of fluorescent protein fusions. Further, the role of the forkhead transcription factor AcFKH1, which directly interacts with CPCR1, was studied by generating an Acfkh1 knockout strain. In contrast to CPCR1, AcFKH1 is not directly involved in the fragmentation of hyphae. Instead, the presence of AcFKH1 seems to be necessary for CPCR1 function in A. chrysogenum morphogenesis, as overexpression of a functional cpcR1 gene in a ΔAcfkh1 background has no effect on arthrospore formation. Moreover, strains lacking Acfkh1 exhibit defects in cell separation, indicating an involvement of the forkhead transcription factor in mycelial growth of A. chrysogenum. Our data offer the potential to control fungal growth in biotechnical processes that require defined morphological stages for optimal production yields.
Anaerobic regulation by an atypical Arc system in Shewanella oneidensis
Authors: Gralnick Jeffrey A. , Brown C. Titus , Newman Dianne K. 
Published: May 2005

Summary Shewanella oneidensis strain MR‐1 is well known for its respiratory versatility, yet little is understood about how it regulates genes involved in anaerobic respiration. The Arc two‐component system plays an important role in this process in Escherichia coli; therefore, we determined its function in S. oneidensis. arcA from S. oneidensis complements an E. coli arcA mutant, but the Arc regulon in S. oneidensis constitutes a different suite of genes. For example, one of the strongest ArcA‐regulated gene clusters in E. coli, sdh, is not regulated by the Arc system in S. oneidensis, and the cyd locus, which is induced by ArcA in E. coli under microaerobic conditions, is repressed by ArcA in S. oneidensis under anaerobic conditions. One locus that we identified as being potentially regulated by ArcA in S. oneidensis contains genes predicted to encode subunits of a dimethyl sulphoxide (DMSO) reductase. We demonstrate that these genes encode a functional DMSO reductase, and that an arcA mutant cannot fully induce their expression and is defective in growing on DMSO under anaerobic conditions. While S. oneidensis lacks a highly conserved full‐length ArcB homologue, ArcA is partially activated by a small protein homologous to the histidine phosphotransfer domain of ArcB from E. coli, HptA. This protein alone is unable to compensate for the lack of arcB in E. coli, indicating that another protein is required in addition to HptA to activate ArcA in S. oneidensis.
Coupling of multicellular morphogenesis and cellular differentiation by an unusual hybrid histidine protein kinase in Myxococcus xanthus
Authors: Rasmussen Anders Aa. , Porter Steven L. , Armitage Judith P. , Søgaard‐Andersen Lotte 
Published: May 2005

SummaryWe describe an unusual hybrid histidine protein kinase, which is important for spatially coupling cell aggregation and sporulation during fruiting body formation in Myxococcus xanthus. A rodK mutant makes abnormal fruiting bodies and spores develop outside the fruiting bodies. RodK is a soluble, cytoplasmic protein, which contains an N‐terminal sensor domain, a histidine protein kinase domain and three receiver domains. In vitro phosphorylation assays showed that RodK possesses kinase activity. Kinase activity is essential for RodK function in vivo. RodK is present in vegetative cells and remains present until the late aggregation stage, after which the level decreases in a manner that depends on the intercellular A‐signal. Genetic evidence suggests that RodK may regulate multiple temporally separated events during fruiting body formation including stimulation of early developmental gene expression, inhibition of A‐signal production and inhibition of the intercellular C‐signal transduction pathway. We speculate that RodK undergoes a change in activity during development, which is reflected in changes in phosphotransfer to the receiver domains.
A glutamate‐alanine‐leucine (EAL) domain protein of Salmonella controls bacterial survival in mice, antioxidant defence and killing of macrophages: role of cyclic diGMP
Authors: Hisert Katherine B. , MacCoss Michael , Shiloh Michael U. , Darwin K. Heran , Singh Shaneen , Jones Roger A. , Ehrt Sabine , Zhang Zhaoying , Gaffney Barbara L. , Gandotra Sheetal , Holden David W. , Murray Diana , Nathan Carl 
Published: May 2005

SummarySignature‐tagged transposon mutagenesis of Salmonella with differential recovery from wild‐type and immunodeficient mice revealed that the gene here named cdgR[for c‐diguanylate (c‐diGMP) regulator] is required for the bacterium to resist host phagocyte oxidase in vivo. CdgR consists solely of a glutamate‐alanine‐leucine (EAL) domain, a predicted cyclic diGMP (c‐diGMP) phosphodiesterase. Disruption of cdgR decreased bacterial resistance to hydrogen peroxide and accelerated bacterial killing of macrophages. An ultrasensitive assay revealed c‐diGMP in wild‐type Salmonella with increased levels in the CdgR‐deficient mutant. Thus, besides its known role in regulating cellulose synthesis and biofilm formation, bacterial c‐diGMP also regulates host–pathogen interactions involving antioxidant defence and cytotoxicity.
The pyruvate kinase of Stigmatella aurantiaca is an indole binding protein and essential for development
Authors: Stamm Irmela , Lottspeich Friedrich , Plaga Wulf 
Published: May 2005

SummaryMyxospore formation of the myxobacterium Stigmatella aurantiaca can be uncoupled from the cooperative development i.e. fruiting body formation, by low concentrations of indole. Two putative indole receptor proteins were isolated by their capacity to bind indole and identified as pyruvate kinase (PK) and aldehyde dehydrogenase. The PK activity of Stigmatella crude extracts was stimulated by indole. Cloning of the PK gene (pykA) and the construction of a pykA disruption mutant strikingly revealed that PK is essential for multicellular development: Fruiting body formation was abolished in the mutant strain and indole‐induced spore formation was delayed. The developmental defects could be complemented by insertion of the pykA gene at the mtaB locus of the Stigmatella genome excluding any polar effects of the pykA disruption.
Leukapheresis for the extraction of monocytes and various lymphocyte subpopulations from peripheral blood: product quality and prediction of the yield using different harvest procedures
Authors: Wolf C. E. , Meyer M. , Riggert J. 
Published: May 2005

Background and Objectives  Leukapheresis of non‐mobilized healthy donors is performed to harvest monocytes and lymphocyte subpopulations for use in various therapeutic regimens. In this methodological study, we compared two different leukapheresis programs, using equivalent volumes of processed blood over similar processing periods, to determine the influence of the procedures on the donor peripheral blood count and to establish the procedure that yields the highest quality product.Materials and Methods  The target variables obtained in 41 healthy blood donors who underwent short‐term leukapheresis (80–105 min) were retrospectively compared. Twenty‐one volunteers were processed on a COBE Spectra™ machine at the MNC setting and 20 volunteers were processed at the AutoPBSC setting. Data were collected on pre‐ and postleukapheresis samples and on the product.Results  AutoPBSC and MNC procedures resulted in a decrease of haemoglobin (5–7%), platelets (17–20%), monocytes (22%) and lymphocytes (23–27%), but not of granulocytes in peripheral blood. Both procedures produced nearly identical leucocyte and lymphocyte yields. AutoPBSC products contained a greater number of granulocytes, monocytes and red cells, but fewer platelets. The preleukapheresis values correlated with the yields for monocytes, T‐helper and T‐suppressor cells, B‐lymphocytes and natural killer cells, but not for granulocytes or platelets.Conclusions Leukapheresis  is a safe and efficient procedure for collecting large numbers of peripheral blood monocytes and different lymphocyte populations from non‐mobilized donors. The two programs yield comparable leucocyte harvests. Based on our results, yields can be predicted from the peripheral cell counts.
Economic values for resistance to gastrointestinal helminths in meat sheep in Kenya
Authors: Gicheha M.G. , Kosgey I.S. , Bebe B.O. , Kahi A.K. 
Published: May 2005

SummaryEconomic values for resistance to gastrointestinal (GI) helminths in meat sheep were estimated based on previously published genetic and phenotypic parameters in a selection index objectively optimizing gains on yearling weight (YW). A two‐trait index of YW and faecal egg count (FEC) were considered when accounting only for tangible roles of sheep production using individual records for index calculation (scheme 1) or including individual, sire, dam and male paternal half‐sib information (scheme 2). Schemes 3 and 4 were similar to schemes 1 and 2, respectively, but accounted for both tangible and intangible roles of sheep production. Economic values within each scheme were estimated for five breeding objectives as follows: (i) index response in YW equals response from single trait selection, (ii) index response in YW is maximum, (iii) the level of FEC was held constant, (iv) A predetermined response of −0.22 (×1000) eggs per gram was assumed and (v) Monetary value of response in FEC is minimum. All estimated economic values were negative, and were Kenya Shillings (KSh) −34.90 (US$−0.50), 0.00, −92.20 (US$−1.32), −153.31 (US$−2.19) and −47.90 (US$−0.68), respectively, for options 1–5 in scheme 1. In all schemes the breeding options ranked 4, 3, 5 and 1 in descending order; however, options 1 and 5 exchanged positions in schemes 2 and 4. Economic values were responsive to changes in heritability of FEC and genetic correlation between the two traits. The magnitude of the economic values reflects the importance of including resistance to GI helminths in the breeding objectives for meat sheep in different production systems.