bluuebunny/crossref_metadata_2025_split huggingface dataset:
Signal Transduction Protein P
II
Phosphatase PphA Is Required for Light-Dependent Control of Nitrate Utilization in
Synechocystis
sp. Strain PCC 6803
Authors: Kloft Nicole , Forchhammer Karl 
Published: September 2005

ABSTRACT

Signal transduction protein P
II
is dephosphorylated in
Synechocystis
sp. strain PCC 6803 by protein phosphatase PphA. To determine the impact of PphA-mediated P
II
dephosphorylation on physiology, the phenotype of a PphA-deficient mutant was analyzed. Mutants lacking either PphA or P
II
were impaired in efficient utilization of nitrate as the nitrogen source. Under conditions of limiting photosystem I (PSI)-reduced ferredoxin, excess reduction of nitrate along with impaired reduction of nitrite occurred in P
II
signaling mutants, resulting in excretion of nitrite to the medium. This effect could be reversed by increasing the level of PSI-reduced ferredoxin. We present evidence that nonphosphorylated P
II
controls the utilization of nitrate in response to low light intensity by tuning down nitrate uptake to meet the actual reduction capacity. This control mechanism can be bypassed by exposing cells to excess levels of nitrate. Uncontrolled nitrate uptake leads to light-dependent nitrite excretion even in wild-type cells, confirming that nitrate uptake controls nitrate utilization in response to limiting photon flux densities.
Cyclic AMP Receptor Protein and RhaR Synergistically Activate Transcription from the
l
-Rhamnose-Responsive
rhaSR
Promoter in
Escherichia coli
Authors: Wickstrum Jason R. , Santangelo Thomas J. , Egan Susan M. 
Published: September 2005

ABSTRACT

The
Escherichia coli rhaSR
operon encodes two AraC family transcription activator proteins, RhaS and RhaR, which regulate expression of the
l
-rhamnose catabolic regulon in response to
l
-rhamnose availability. RhaR positively regulates
rhaSR
in response to
l
-rhamnose, and RhaR activation can be enhanced by the cyclic AMP (cAMP) receptor protein (CRP) protein. CRP is a well-studied global transcription regulator that binds to DNA as a dimer and activates transcription in the presence of cAMP. We investigated the mechanism of CRP activation at
rhaSR
both alone and in combination with RhaR in vivo and in vitro. Base pair substitutions at potential CRP binding sites in the
rhaSR-rhaBAD
intergenic region demonstrate that CRP site 3, centered at position −111.5 relative to the
rhaSR
transcription start site, is required for the majority of the CRP-dependent activation of
rhaSR
. DNase I footprinting confirms that CRP binds to site 3; CRP binding to the other potential CRP sites at
rhaSR
was not detected. We show that, at least in vitro, CRP is capable of both RhaR-dependent and RhaR-independent activation of
rhaSR
from a total of three transcription start sites. In vitro transcription assays indicate that the carboxy-terminal domain of the alpha subunit (α-CTD) of RNA polymerase is at least partially dispensable for RhaR-dependent activation but that the α-CTD is required for CRP activation of
rhaSR
. Although CRP requires the presence of RhaR for efficient in vivo activation of
rhaSR
, DNase I footprinting assays indicated that cooperative binding between RhaR and CRP does not make a significant contribution to the mechanism of CRP activation at
rhaSR
. It therefore appears that CRP activates transcription from
rhaSR
as it would at simple class I promoters, albeit from a relatively distant position.
Identification of theBacillus anthracisγ Phage Receptor
Authors: Davison Sophie , Couture-Tosi Evelyne , Candela Thomas , Mock Michèle , Fouet Agnès 
Published: September 2005

ABSTRACTBacillus anthracis, a gram-positive, spore-forming bacterium, is the etiological agent of anthrax. It belongs to theBacillus cereusgroup, which also containsBacillus cereusandBacillus thuringiensis. MostB. anthracisstrains are sensitive to phage γ, but mostB. cereusandB. thuringiensisstrains are resistant to the lytic action of phage γ. Here, we report the identification of a protein involved in the bacterial receptor for the γ phage, which we term GamR (Gamma phagereceptor). It is an LPXTG protein (BA3367, BAS3121) and is anchored by the sortase A. AB. anthracissortase A mutant is not as sensitive as the parental strain nor as the sortase B and sortase C mutants, whereas the GamR mutant is resistant to the lytic action of the phage. Electron microscopy reveals the binding of the phage to the surface of the parental strain and its absence from the GamR mutant. SpontaneousB. anthracismutants resistant to the phage harbor mutations in the gene encoding the GamR protein. AB. cereusstrain that is sensitive to the phage possesses a protein similar (89% identity) to GamR.B. thuringiensis97-27, a strain which, by sequence analysis, is predicted to harbor a GamR-like protein, is resistant to the phage but nevertheless displays phage binding.
Lactate Racemization as a Rescue Pathway for Supplying
d
-Lactate to the Cell Wall Biosynthesis Machinery in
Lactobacillus plantarum
Authors: Goffin Philippe , Deghorain Marie , Mainardi Jean-Luc , Tytgat Isabelle , Champomier-Vergès Marie-Christine , Kleerebezem Michiel , Hols Pascal 
Published: September 2005

ABSTRACT

Lactobacillus plantarum
is a lactic acid bacterium that produces
d
- and
l
-lactate using stereospecific NAD-dependent lactate dehydrogenases (LdhD and LdhL, respectively). However, reduction of glycolytic pyruvate by LdhD is not the only pathway for
d
-lactate production since a mutant defective in this activity still produces both lactate isomers (T. Ferain, J. N. Hobbs, Jr., J. Richardson, N. Bernard, D. Garmyn, P. Hols, N. E. Allen, and J. Delcour, J. Bacteriol. 178:5431-5437, 1996). Production of
d
-lactate in this species has been shown to be connected to cell wall biosynthesis through its incorporation as the last residue of the muramoyl-pentadepsipeptide peptidoglycan precursor. This particular feature leads to natural resistance to high concentrations of vancomycin. In the present study, we show that
L. plantarum
possesses two pathways for
d
-lactate production: the LdhD enzyme and a lactate racemase, whose expression requires
l
-lactate. We report the cloning of a six-gene operon, which is involved in lactate racemization activity and is positively regulated by
l
-lactate. Deletion of this operon in an
L. plantarum
strain that is devoid of LdhD activity leads to the exclusive production of
l
-lactate. As a consequence, peptidoglycan biosynthesis is affected, and growth of this mutant is
d
-lactate dependent. We also show that the growth defect can be partially restored by expression of the
d
-alanyl-
d
-alanine-forming Ddl ligase from
Lactococcus lactis
, or by supplementation with various
d
-2-hydroxy acids but not
d
-2-amino acids, leading to variable vancomycin resistance levels. This suggests that
L. plantarum
is unable to efficiently synthesize peptidoglycan precursors ending in
d
-alanine and that the cell wall biosynthesis machinery in this species is specifically dedicated to the production of peptidoglycan precursors ending in
d
-lactate. In this context, the lactate racemase could thus provide the bacterium with a rescue pathway for
d
-lactate production upon inactivation or inhibition of the LdhD enzyme.
A Periplasmic Drug-Binding Site of the AcrB Multidrug Efflux Pump: a Crystallographic and Site-Directed Mutagenesis Study
Authors: Yu Edward W. , Aires Julio R. , McDermott Gerry , Nikaido Hiroshi 
Published: September 2005

ABSTRACT

The
Escherichia coli
AcrB multidrug efflux pump is a membrane protein that recognizes many structurally dissimilar toxic compounds. We previously reported the X-ray structures of four AcrB-ligand complexes in which the ligands were bound to the wall of the extremely large central cavity in the transmembrane domain of the pump. Genetic studies, however, suggested that discrimination between the substrates occurs mainly in the periplasmic domain rather than the transmembrane domain of the pump. We here describe the crystal structures of the AcrB mutant in which Asn109 was replaced by Ala, with five structurally diverse ligands, ethidium, rhodamine 6G, ciprofloxacin, nafcillin, and Phe-Arg-β-naphthylamide. The ligands bind not only to the wall of central cavity but also to a new periplasmic site within the deep external depression formed by the C-terminal periplasmic loop. This depression also includes residues identified earlier as being important in the specificity. We show here that conversion into alanine of the Phe664, Phe666, or Glu673 residue in the periplasmic binding site produced significant decreases in the MIC of most agents in the N109A background. Furthermore, decreased MICs were also observed when these residues were mutated in the wild-type AcrB background, although the effects were more modest. The MIC data were also confirmed by assays of ethidium influx rates in intact cells, and our results suggest that the periplasmic binding site plays a role in the physiological process of drug efflux.
Mutator Phenotype Resulting from DNA Polymerase IV Overproduction in
Escherichia coli
: Preferential Mutagenesis on the Lagging Strand
Authors: Kuban Wojciech , Banach-Orlowska Magdalena , Bialoskorska Malgorzata , Lipowska Aleksandra , Schaaper Roel M. , Jonczyk Piotr , Fijalkowska Iwona J. 
Published: September 2005

ABSTRACT

We investigated the mutator effect resulting from overproduction of
Escherichia coli
DNA polymerase IV. Using
lac
mutational targets in the two possible orientations on the chromosome, we observed preferential mutagenesis during lagging strand synthesis. The mutator activity likely results from extension of mismatches produced by polymerase III holoenzyme.
Rise-Time Elongation Effects on Trapped Field and Temperature Rise in Pulse Field Magnetization for High Temperature Superconducting Bulk
Authors: Fujishiro Hiroyuki , Kaneyama Masahiko , Yokoyama Kazuya , Oka Tetsuo , Noto Koshichi 
Published: September 2005

Pulse field magnetization (PFM) using a magnetic pulse of B
ex=3.83–5.53 T with various rise times t
r (=6–20 ms) has been performed for the cryocooled SmBaCuO bulk superconductor starting at the initial temperature of 40 K. The time evolutions of temperature T(t) and local field B
L
P(t) have been measured on the bulk surface after applying the magnetic pulse. With increasing t
r, the temperature rise ΔT and the trapped field B
T
P increase for B
ex≤4.70 T and decrease for B
ex=5.53 T. The rise time t
r required to realize the optimum B
T
P has been found to become longer for a smaller pulse field B
ex. From the analyses of the generated heat Q after five successive applications of pulses (Nos. 1–5) with the same amplitude, the Q(No. 5) value, which can be regarded as the viscous loss Q
v, decreases with increasing t
r, due mainly to the decrease in the flux propagation velocity v in the bulk with longer t
r.
Hyperthermia-Induced Proteasome Inhibition and Loss of Androgen Receptor Expression in Human Prostate Cancer Cells
Authors: Pajonk Frank , van Ophoven Arndt , McBride William H. 
Published: September 2005

Abstract
Prostate cancer is the second leading cause of death in men in western countries and is usually treated by surgery and/or radiotherapy. More recently, hyperthermia has been introduced into clinical trials investigating a possible effect in the first-line treatment of prostate cancer. However, the molecular mechanisms of hyperthermia are not completely understood. In this study, we investigated the effects of hyperthermia on proteasome function and its significance for signal transduction, cell death and androgen receptor (AR) expression in PC-3, LnCaP, and DU-145 human and TRAMP-C2 murine prostate cancer cells. Hyperthermia caused apoptosis and radiosensitization and decreased 26S proteasome activity in all three human cell lines to about 40% of untreated control cells. 20S proteasome activity was not affected by heat. Heat treatment inhibited constitutive and radiation-induced activation of nuclear factor κB caused by stabilization of IκB. Although stabilization of AR by proteasome inhibitors has been reported previously, AR protein levels in LnCaP cells decreased dramatically after heat. Our data suggest that inhibition of proteasome function and dependent signal transduction pathways might be a major molecular mechanisms of heat-induced apoptosis and radiosensitization. Hyperthermia abrogates AR expression in androgen-dependent cells and might thus promote malignant progression of prostate cancer.
Coexpression of Cyclooxygenases (COX-1, COX-2) and Vascular Endothelial Growth Factors (VEGF-A, VEGF-C) in Esophageal Adenocarcinoma
Authors: von Rahden Burkhard H.A. , Stein Hubert J. , Pühringer Franziska , Koch Ina , Langer Rupert , Piontek Guido , Siewert J. Rüdiger , Höfler Heinz , Sarbia Mario 
Published: September 2005

Abstract
Cyclooxygenases (COX), especially COX-2, are considered to be involved in carcinogenesis. Our study was initiated to test whether expression of COX isoforms (COX-1 and COX-2) is linked to expression of potent inducers of angiogenesis [vascular endothelial growth factor (VEGF)-A] and lymphangiogenesis (VEGF-C) in esophageal adenocarcinoma. One hundred twenty-three esophageal adenocarcinomas were investigated by means of quantitative reverse transcription-PCR for expression of COX-1, COX-2, VEGF-A, and VEGF-C. Additionally, COX-2 protein expression was determined using immunohistochemistry. Three esophageal cancer cell lines (OE-33, OSC-1, and OSC-2) were treated with COX-inhibiting substances (diclofenac, rofecoxib, and SC-560) and the effect on expression of the four genes was determined. COX-2 protein expression was found in all carcinomas under analysis. RNA expression levels of COX-1 and COX-2 varied markedly in carcinoma tissues and correlated significantly with each other (P &lt; 0.001, r = 0.726). Furthermore, COX expression correlated with expression of VEGF-A (COX-1: P &lt; 0.001, r = 0.753; COX-2: P &lt; 0.001, r = 0.764) and VEGF-C (COX-1: P &lt; 0.001, r = 0.778; COX-2: P &lt; 0.001; r = 0.613). Exposure of esophageal cancer cell lines OE-33, OSC-1, and OSC-2 with three COX-inhibiting substances (diclofenac, rofecoxib, and SC-560) resulted in significantly reduced expression of VEGF-A and VEGF-C. In conclusion, our data suggest that both COX isoforms may be involved in the pathogenesis of esophageal adenocarcinoma, as they are linked to the expression of important modulators of angiogenesis (VEGF-A) and lymphangiogenesis (VEGF-C).
A Mouse Model of Human Breast Cancer Metastasis to Human Bone
Authors: Kuperwasser Charlotte , Dessain Scott , Bierbaum Benjamin E. , Garnet Dan , Sperandio Kara , Gauvin Gregory P. , Naber Stephen P. , Weinberg Robert A. , Rosenblatt Michael 
Published: September 2005

Abstract
Currently, an in vivo model of human breast cancer metastasizing from the orthotopic site to bone does not exist, making it difficult to study the many steps of skeletal metastasis. Moreover, models used to identify the mechanisms by which breast cancer metastasizes to bone are limited to intracardiac injection, which seeds the cancer cells directly into the circulation, thus bypassing the early steps in the metastatic process. Such models do not reflect the full process of metastasis occurring in patients. We have developed an animal model of breast cancer metastasis in which the breast cancer cells and the bone target of osteotropic metastasis are both of human origin. The engrafted human bone is functional, based on finding human IgG in the mouse bloodstream, human B cells in the mouse spleen, and normal bone histology. Furthermore, orthotopic injection of a specific human breast cancer cell line, SUM1315 (derived from a metastatic nodule in a patient), later resulted in both bone and lung metastases. In the case of bone, metastasis was to the human implant and not the mouse skeleton, indicating a species-specific osteotropism. This model replicates the events observed in patients with breast cancer skeletal metastases and serves as a useful and relevant model for studying the disease.
A Gene Expression Signature for Relapse of Primary Wilms Tumors
Authors: Li Wenliang , Kessler Patricia , Yeger Herman , Alami Jennifer , Reeve Anthony E. , Heathcott Rosemary , Skeen Jane , Williams Bryan R.G. 
Published: September 2005

Abstract
Anaplastic histology and metastasis are each associated with higher relapse and mortality rates in Wilms tumor patients. However, not all anaplastic tumors relapse and some nonanaplastic tumors relapse unexpectedly. To identify more accurate early prognostic indicators, we analyzed expression of 4,900 cancer-related genes in 26 primary Wilms tumors. This analysis revealed that expression of a set of four genes predicts future relapse of primary Wilms tumors with high accuracy, independent of anaplasia. Random permutation testing of this prognostic gene expression signature yielded P = 0.003. Real-time reverse transcription-PCR analysis of the four genes in an independent primary tumor set resulted in correct prediction of future relapse with an accuracy of 92%. One of the four genes in the prognostic signature, CCAAT/enhancer binding protein β (C/EBPB), is expressed at higher levels in both primary relapsing tumors and metastatic tumors than in primary nonrelapsing tumors. Short interfering RNA–mediated down-regulation of C/EBPB expression in WiT49, a cell line derived from a metastatic Wilms tumor, resulted in spontaneous apoptosis. These findings suggest that C/EBPB is a critical survival factor for Wilms tumor cells and that its expression contributes to the prognosis of Wilms tumor patients.
Lack of Telopeptides in Fibrillar Collagen I Promotes the Invasion of a Metastatic Breast Tumor Cell Line
Authors: Demou Zoe N. , Awad Michael , McKee Trevor , Perentes Jean Yannis , Wang Xiaoye , Munn Lance L. , Jain Rakesh K. , Boucher Yves 
Published: September 2005

Abstract
Defective fibrillar collagen polymerization in primary tumors has been correlated with increased metastasis. However, it is unclear how collagen organization influences tumor invasion. In this study, we show that collagen I polymerized without telopeptides (the flanking regions of collagen molecules) can differentially affect the three-dimensional migration of mammary carcinoma cells. MDA-MB-231 cells capable of proteolytic degradation and mesenchymal motion, invaded telopeptide-intact and telopeptide-free collagen gels to the same extent. In contrast, MDA-MB-435S cells, with typical features of amoeboid cells (poor collagenolytic activity, rounded cell morphology), were 5-fold more invasive in telopeptide-free than telopeptide-intact collagen. A fraction of the MDA-MB-435S cells that invaded telopeptide-intact or telopeptide-free collagen had a rounded morphology; however, in telopeptide-free collagen, a significant fraction of the cells switched from a rounded to elongated morphology (protrusion formation). The dynamic changes in cellular shape facilitated MDA-MB-435S locomotion through the narrow interfiber gaps, which were smaller than cell diameters. Based on the spherical morphology of MDA-MB-435S cells, we tested if the changes in cell shape and invasion were related to RhoA-ROCK activity; GTP-bound RhoA was measured in pull-down assays. RhoA activity was 1.8-fold higher for MDA-MB-435S cells seeded on telopeptide-free than telopeptide-intact collagen. Y27632 inhibition of ROCK, a Rho effector, significantly reduced the changes in cellular morphodynamics and the invasion of MDA-MB-435S cells but did not alter the invasion of MDA-MB-231 cells. Thus, the higher RhoA activity of MDA-MB-435S cells in telopeptide-free collagen enhances the changes in cellular morphodynamics associated with motility and invasion.
A 27-Amino-Acid Synthetic Peptide Corresponding to the NH2-Terminal Zinc-Binding Domain of Endostatin Is Responsible for Its Antitumor Activity
Authors: Tjin Tham Sjin Robert M. , Satchi-Fainaro Ronit , Birsner Amy E. , Ramanujam V.M. Sadagopa , Folkman Judah , Javaherian Kashi 
Published: September 2005

Abstract
The first recombinant endostatin that elicited strong antitumor activity was expressed in Escherichia coli and administered as a suspension. Under these conditions, the protein retained its full antiangiogenic activity. Lack of requirement for a folded structure prompted us to investigate antitumor properties of synthetic peptides corresponding to different regions of endostatin. Here, we show that the entire antitumor, antimigration, and antipermeability activities of endostatin are mimicked by a 27-amino-acid peptide corresponding to the NH2-terminal domain of endostatin. This peptide contains three histidines that are responsible for zinc binding. Mutations of the zinc-binding histidines abolished its antitumor and antimigration activities, but not antipermeability properties.
Macrophages Promote the Invasion of Breast Carcinoma Cells via a Colony-Stimulating Factor-1/Epidermal Growth Factor Paracrine Loop
Authors: Goswami Sumanta , Sahai Erik , Wyckoff Jeffrey B. , Cammer Michael , Cox Dianne , Pixley Fiona J. , Stanley E. Richard , Segall Jeffrey E. , Condeelis John S. 
Published: September 2005

Abstract
Previous studies have shown that macrophages and tumor cells are comigratory in mammary tumors and that these cell types are mutually dependent for invasion. Here we show that macrophages and tumor cells are necessary and sufficient for comigration and invasion into collagen I and that this process involves a paracrine loop. Macrophages express epidermal growth factor (EGF), which promotes the formation of elongated protrusions and cell invasion by carcinoma cells. Colony stimulating factor 1 (CSF-1) produced by carcinoma cells promotes the expression of EGF by macrophages. In addition, EGF promotes the expression of CSF-1 by carcinoma cells thereby generating a positive feedback loop. Disruption of this loop by blockade of either EGF receptor or CSF-1 receptor signaling is sufficient to inhibit both macrophage and tumor cell migration and invasion.
Tumor Necrosis Factor–Related Apoptosis-Inducing Ligand Alters Mitochondrial Membrane Lipids
Authors: Sandra Ferry , Degli Esposti Mauro , Ndebele Kenneth , Gona Philimon , Knight David , Rosenquist Magnus , Khosravi-Far Roya 
Published: September 2005

AbstractTumor necrosis factor–related apoptosis-inducing ligand (TRAIL) has been shown to have selective antitumor activity. TRAIL induces ubiquitous pathways of cell death in which caspase activation is mediated either directly or via the release of apoptogenic factors from mitochondria; however, the precise components of the mitochondrial signaling pathway have not been well defined. Notably, mitochondria constitute an important target in overcoming resistance to TRAIL in many types of tumors. Bid is considered to be fundamental in engaging mitochondria during death receptor–mediated apoptosis, but this action is dependent on mitochondrial lipids. Here, we report that TRAIL signaling induces an alteration in mitochondrial membrane lipids, particularly cardiolipin. This occurs independently of caspase activation and primes mitochondrial membranes to the proapoptotic action of Bid. We unveil a link between TRAIL signaling and alteration of membrane lipid homeostasis that occurs in parallel to apical caspase activation but does not take over the mode of cell death because of the concurrent activation of caspase-8. In particular, TRAIL-induced alteration of mitochondrial lipids follows an imbalance in the cellular homeostasis of phosphatidylcholine, which results in an elevation in diacylglycerol (DAG). Elevated DAG in turn activates the δ isoform of phospholipid-dependent serine/threonine protein kinase C, which then accelerates the cleavage of caspase-8. We also show that preservation of phosphatidylcholine homeostasis by inhibition of lipid-degrading enzymes almost completely impedes the activation of pro-caspase-9 while scarcely changing the activation of caspase-8.