bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of the Intramolecular Disulfide Bond in FlgI, the Flagellar P-Ring Component of
Escherichia coli
Authors: Hizukuri Yohei , Yakushi Toshiharu , Kawagishi Ikuro , Homma Michio 
Published: June 2006

ABSTRACT

The P ring of the bacterial flagellar motor consists of multiple copies of FlgI, a periplasmic protein. The intramolecular disulfide bond in FlgI has previously been reported to be essential for P-ring assembly in
Escherichia coli
, because the P ring was not assembled in a
dsbB
strain that was defective for disulfide bond formation in periplasmic proteins. We, however, found that the two Cys residues of FlgI are not conserved in other bacterial species. We then assessed the role of this intramolecular disulfide bond in FlgI. A Cys-eliminated FlgI derivative formed a P ring that complemented the flagellation defect of our Δ
flgI
strain when it was overproduced, suggesting that disulfide bond formation in FlgI is not absolutely required for P-ring assembly. The levels of the mature forms of the FlgI derivatives were significantly lower than that of wild-type FlgI, although the precursor protein levels were unchanged. Moreover, the FlgI derivatives were more susceptible to degradation than wild-type FlgI. Overproduction of FlgI suppressed the motility defect of Δ
dsbB
cells. Additionally, the low level of FlgI observed in the Δ
dsbB
strain increased in the presence of
l
-cystine, an oxidative agent. We propose that intramolecular disulfide bond formation facilitates the rapid folding of the FlgI monomer to protect against degradation in the periplasmic space, thereby allowing its efficient self-assembly into the P ring.
Global Transcriptome Analysis of the Cold Shock Response of
Shewanellaoneidensis
MR-1 and Mutational Analysis of Its ClassicalCold ShockProteins
Authors: Gao Haichun , Yang Zamin K. , Wu Liyou , Thompson Dorothea K. , Zhou Jizhong 
Published: June 2006

ABSTRACT

This
study presents a global transcriptional analysis of the cold shock
response of
Shewanella oneidensis
MR-1 after a temperature
downshift from 30°C to 8 or 15°C based on time series
microarray experiments. More than 700 genes were found to be
significantly affected (
P
≤ 0.05) upon cold shock
challenge, especially at 8°C. The temporal gene expression
patterns of the classical cold shock genes varied, and only some of
them, most notably so1648 and so2787, were differentially regulated in
response to a temperature downshift. The global response of
S.
oneidensis
to cold shock was also characterized by the
up-regulation of genes encoding membrane proteins, DNA metabolism and
translation apparatus components, metabolic proteins, regulatory
proteins, and hypothetical proteins. Most of the metabolic proteins
affected are involved in catalytic processes that generate NADH or
NADPH. Mutational analyses confirmed that the small cold shock
proteins, So1648 and So2787, are involved in the cold shock response of
S. oneidensis
. The analyses also indicated that So1648 may
function only at very low
temperatures.
Characterization of a Novel Partition System Encoded by the δ and ω Genes from the Streptococcal Plasmid pSM19035
Authors: Dmowski Michał , Sitkiewicz Izabela , Cegłowski Piotr 
Published: June 2006

ABSTRACTHigh segregational stability of the streptococcal plasmid pSM19035 is achieved by the concerted action of systems involved in plasmid copy number control, multimer resolution, and postsegregational killing. In this study, we demonstrate the role of two genes,δandω, in plasmid stabilization by a partition mechanism. We show that these two genes can stabilize the native pSM19035 replicon as well as other θ- and σ-type plasmids inBacillus subtilis. In contrast to other known partition systems, in this case the two genes are transcribed separately; however, they are coregulated by the product of theparB-like geneω. Analysis of mutants of theparA-like geneδshowed that the Walker A ATPase motif is necessary for plasmid stabilization. The ParB-like product of theωgene binds to three regions containing repeated WATCACW heptamers, localized in thecopS(regulation of plasmid copy number),δ, andωpromoter regions. We demonstrate that all three of these regions can cause partition-mediated incompatibility. Moreover, our data suggest that each of these could play the role of a centromere-like sequence. We conclude thatδandωconstitute a novel type of plasmid stabilization system.
CbrA Is a Stationary-Phase Regulator of Cell Surface Physiology and Legume Symbiosis in
Sinorhizobium meliloti
Authors: Gibson Katherine E. , Campbell Gordon R. , Lloret Javier , Walker Graham C. 
Published: June 2006

ABSTRACT

Sinorhizobium meliloti
produces an exopolysaccharide called succinoglycan that plays a critical role in promoting symbiosis with its host legume, alfalfa (
Medicago sativa
). We performed a transposon mutagenesis and screened for mutants with altered succinoglycan production and a defect in symbiosis. In this way, we identified a putative two-component histidine kinase associated with a PAS sensory domain, now designated CbrA (
c
alcofluor-
b
right
r
egulator
A
). The
cbrA
::Tn
5
mutation causes overproduction of succinoglycan and results in increased accumulation of low-molecular-weight forms of this exopolysaccharide. Our results suggest the
cbrA
::Tn
5
allele leads to this succinoglycan phenotype through increased expression of
exo
genes required for succinoglycan biosynthesis and modification. Interestingly, CbrA-dependent regulation of
exo
and
exs
genes is observed almost exclusively during stationary-phase growth. The
cbrA
::Tn
5
mutant also has an apparent cell envelope defect, based on increased sensitivity to a number of toxic compounds, including the bile salt deoxycholate and the hydrophobic dye crystal violet. Growth of the
cbrA
mutant is also slowed under oxidative-stress conditions. The CbrA-regulated genes
exsA
and
exsE
encode putative inner membrane ABC transporters with a high degree of similarity to lipid exporters. ExsA is homologous to the
Escherichia coli
MsbA protein, which is required for lipopolysacharide transport, while ExsE is a member of the eukaryotic family of ABCD/hALD peroxisomal membrane proteins involved in transport of very long-chain fatty acids, which are a unique component of the lipopolysaccharides of alphaproteobacteria. Thus, CbrA could play a role in regulating the lipopolysaccharide or lipoprotein components of the cell envelope.
Structure of the θ Subunit ofEscherichia coliDNA Polymerase III in Complex with the ε Subunit
Authors: Keniry Max A. , Park Ah Young , Owen Elisabeth A. , Hamdan Samir M. , Pintacuda Guido , Otting Gottfried , Dixon Nicholas E. 
Published: June 2006

ABSTRACTThe catalytic core ofEscherichia coliDNA polymerase III contains three tightly associated subunits, the α, ε, and θ subunits. The θ subunit is the smallest and least understood subunit. The three-dimensional structure of θ in a complex with the unlabeled N-terminal domain of the ε subunit, ε186, was determined by multidimensional nuclear magnetic resonance spectroscopy. The structure was refined using pseudocontact shifts that resulted from inserting a lanthanide ion (Dy3+, Er3+, or Ho3+) at the active site of ε186. The structure determination revealed a three-helix bundle fold that is similar to the solution structures of θ in a methanol-water buffer and of the bacteriophage P1 homolog, HOT, in aqueous buffer. Conserved nuclear Overhauser enhancement (NOE) patterns obtained for free and complexed θ show that most of the structure changes little upon complex formation. Discrepancies with respect to a previously published structure of free θ (Keniry et al., Protein Sci.9:721-733, 2000) were attributed to errors in the latter structure. The present structure satisfies the pseudocontact shifts better than either the structure of θ in methanol-water buffer or the structure of HOT. satisfies these shifts. The epitope of ε186 on θ was mapped by NOE difference spectroscopy and was found to involve helix 1 and the C-terminal part of helix 3. The pseudocontact shifts indicated that the helices of θ are located about 15 Å or farther from the lanthanide ion in the active site of ε186, in agreement with the extensive biochemical data for the θ-ε system.
Spindle cell carcinoma of head and neck: an immunohistochemical and molecular approach to its pathogenesis
Authors: Gupta Ruchika , Singh Sompal , Hedau Suresh , Nigam Sonu , Das Bhudev C , Singh Ishwar , Mandal Ashish Kumar 
Published: May 2006

Background:Spindle cell carcinoma (SpCC) is a rare microscopic type of cancer of the mouth and oropharynx. Although SpCC is thought to arise from squamous cell carcinoma (SCC), it carries a worse prognosis.Aim:To find out the difference in immunohistochemical expression of cytokeratin, vimentin and smooth-muscle actin, and mutational alterations in the K-ras oncogene between the two tumours, in an attempt to characterise SpCC.Methods:Immunohistochemical analysis was performed by standard avidin–biotin complex method in 35 cases each of SpCCs and SCCs. DNA extracted from paraffin wax-embedded tumours was used for PCR followed by single-strand conformation polymorphism for mutational analysis of K-ras exon 1 and exon 2.Results:In the SpCC group, cytokeratin positivity was significantly higher in epithelial areas (52.2%) than in spindle cell areas (16.1%), whereas vimentin was more positive in spindle cell areas (18.7%) than epithelial areas (2.7%). Cells intermediate between epithelial and spindle cell areas were consistently positive for both cytokeratin and vimentin. Cytokeratin was found to be significantly more positive in SCC (72.6%) than the squamous component and spindle cell component of SpCC. In this study, no mutation was detected in the K-ras gene of either the SpCC or SCC group.Conclusions:The spindle cell component of SpCC is intermixed with cells that are morphologically mesenchymal but express dual antigen-positivity characteristic of epithelial (cytokeratin) and mesenchymal (vimentin) cells. These, possibly, are cells in transition suggesting that SpCC may be a sarcomatous metaplasia of SCC.
Epidermal Growth Factor Receptor Signaling Is Up-regulated in Human Colonic Aberrant Crypt Foci
Authors: Cohen Greg , Mustafi Reba , Chumsangsri Anusara , Little Nathaniel , Nathanson Jeff , Cerda Sonia , Jagadeeswaran Sujatha , Dougherty Urszula , Joseph Loren , Hart John , Yerian Lisa , Tretiakova Maria , Yuan Weihua , Obara Piotr , Khare Sharad , Sinicrope Frank A. , Fichera Alessandro , Boss Gerry R. , Carroll Robert , Bissonnette Marc 
Published: June 2006

Abstract
Aberrant crypt foci (ACF) are collections of abnormal colonic crypts with heterogeneous molecular and pathologic characteristics. Large and dysplastic ACF are putative precursors of colon cancer with neoplastic risk related to increased proliferation. In this study, we examined the role of epidermal growth factor receptor (EGFR) signaling in regulating ACF proliferation. Using magnification chromoendoscopy, we collected large ACF with endoscopic features of dysplasia and separately biopsied adjacent mucosa. Transcript levels were measured by real-time PCR, proteins were assessed by Western blotting, and levels were expressed as fold changes of adjacent mucosa. K-ras and B-Raf mutations were assessed by PCR and Ras activation by the ratio Ras-GTP / (Ras-GTP + Ras-GDP). At the RNA level, 38% of ACF were hyperproliferative, with proliferating cell nuclear antigen (PCNA) mRNA ≥2-fold of adjacent mucosa. Hyperproliferative ACF had significantly increased mRNA levels of EGFR (6.0 ± 1.7–fold), transforming growth factor-α (14.4 ± 5.0–fold), heparin-binding EGF-like growth factor (4.5 ± 1.4–fold), cyclin D1 (4.6 ± 0.7–fold), and cyclooxygenase-2 (COX-2; 9.3 ± 4.2–fold; P &lt; 0.05). At the protein level, 46% of ACF were hyperproliferative (PCNA, 3.2 ± 1.2–fold). In hyperproliferative ACF, 44% possessed significant increases in four EGFR signaling components: EGFR (9.5 ± 1.3–fold), phosphoactive ErbB2 (2.6 ± 0.4–fold), phosphoactive extracellular signal-regulated kinase (3.7 ± 1.1–fold), and cyclin D1 (3.4 ± 0.8–fold; P &lt; 0.05). Ras was activated in 46% of ACF (3.2 ± 0.4–fold; P &lt; 0.05), but K-ras mutations were present in only 7% of ACF. In contrast to COX-2 mRNA, the protein was not increased in hyperproliferative ACF. In summary, we have shown that ACF with up-regulated PCNA possess increased EGFR signaling components that likely contribute to the enhanced proliferative state of dysplastic-appearing ACF. (Cancer Res 2006; 66(11): 5656-64)
SV40 T/t-Common Polypeptide Specifically Induces Apoptosis in Human Cancer Cells that Overexpress HER2/neu
Authors: Wen Chun-Chiang , Cheng Shih-An , Hsuen Shu-Ping , Huang Ya-Ling , Kuo Zong-Keng , Lee Hsin-Fang , Kuo Chou-Hua , Du Jia-Ling , Wang Won-Bo 
Published: June 2006

Abstract
Previously, we reported that SV40 T/t-common polypeptide, which contains the NH2-terminal common domain of SV40 large T and small t antigens, can repress HER2/neu (also known as erbB-2) expression and consequently suppress the tumorigenic potential of the HER2/neu-overexpressing ovarian carcinoma cells. Here we report that T/t-common could specifically induce apoptosis in HER2/neu-overexpressing human cancer cell lines but not in nontransformed cell lines and HER2/neu low-expressing human cancer cell lines. The ability of T/t-common to induce apoptosis in HER2/neu-overexpressing cancer cells was derived from its ability to inhibit HER2/neu because reexpression of a large amount of HER2/neu could block apoptosis induced by T/t-common. T/t-common expression in HER2/neu-overexpressing SK-OV-3 cancer cells led to down-regulation of Bcl-2 and Bcl-XL, and overexpression of Bcl-2 could inhibit the ability of T/t-common to induce apoptosis in these cells. Therefore, the apoptosis-inducing activity of T/t-common is related to its ability to inhibit Bcl-2 expression in HER2/neu-overexpressing cancer cells. Consistent with the apoptosis-inducing activity of T/t-common, we found that T/t-common could specifically inhibit the soft-agarose colony-forming ability of the HER2/neu-overexpressing human cancer cell lines but not that of the HER2/neu low-expressing human cancer cell lines. Finally, we showed that T/t-common could specifically sensitize HER2/neu-overexpressing human cancer cell lines, but not HER2/neu low-expressing human cancer cell lines, to chemotherapeutic agent etoposide. Together, these data suggest that T/t-common alone or in combination with chemotherapy may provide a new approach for treatment of cancers that overexpress HER2/neu. (Cancer Res 2006; 66(11): 5847-57)
BCR-ABL Is Not an Immunodominant Antigen in Chronic Myelogenous Leukemia
Authors: Grünebach Frank , Mirakaj Valbona , Mirakaj Valdete , Müller Martin R. , Brümmendorf Tim , Brossart Peter 
Published: June 2006

Abstract
In the present study, we analyzed the involvement of the BCR-ABL protein in the induction of antigen-specific CTL in order to develop an immunotherapeutic approach in patients with chronic myelogenous leukemia (CML). To accomplish this, we generated dendritic cells (DC) in vitro and electroporated them with various sources of RNA harboring the chimeric bcr-abl transcript. These genetically engineered DCs were used as antigen-presenting cells for the induction of CTLs. By applying this approach, we found that the CTLs induced by DCs transfected with RNA extracted from bcr-abl–positive K-562 cells or CML blasts lysed DCs transfected with the corresponding RNA, but failed to recognize epitopes derived from the chimeric BCR-ABL fusion protein in 51Cr-release assays. In contrast, they were able to lyse autologous DCs electroporated with RNA isolated from patients with acute myeloid leukemia, indicating that antigens shared among these malignant cells are involved and recognized by these CTLs. In patients with CML in complete cytogenetic remission during IFN-α treatment, we detected some reactivity of CD8+ T cells against BCR-ABL in IFN-γ ELISPOT assays, which was weaker as compared with proteinase 3 (PR3)- or prame-directed responses, suggesting that the BCR-ABL protein is less immunogenic as compared with other CML-derived antigens. (Cancer Res 2006; 66(11): 5892-900)
Elevated Expression of Mitogen-Activated Protein Kinase Phosphatase 3 in Breast Tumors: A Mechanism of Tamoxifen Resistance
Authors: Cui Yukun , Parra Irma , Zhang Mao , Hilsenbeck Susan G. , Tsimelzon Anna , Furukawa Toru , Horii Akira , Zhang Zhong-Yin , Nicholson Robert I. , Fuqua Suzanne A.W. 
Published: June 2006

AbstractAntiestrogen resistance is a major clinical problem in the treatment of breast cancer. Altered growth factor signaling with estrogen receptor (ER)-α is associated with the development of resistance. Gene expression profiling was used to identify mitogen-activated protein kinase (MAPK) phosphatase 3 (MKP3) whose expression was correlated with response to the antiestrogen tamoxifen in both patients and in vitro–derived cell line models. Overexpression of MKP3 rendered ER-α-positive breast cancer cells resistant to the growth-inhibitory effects of tamoxifen and enhanced tamoxifen agonist activity in endometrial cells. MKP3 overexpression was associated with lower levels of activated extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation in the presence of estrogen but that estrogen deprivation and tamoxifen treatment decreased MKP3 phosphatase activity, leading to an up-regulation of pERK1/2 MAPK, phosphorylated Ser118-ER-α, and cyclin D1. The MAPK/ERK kinase inhibitor PD98059 blocked tamoxifen-resistant growth. Accumulation of reactive oxygen species was observed with tamoxifen treatment of MKP3-overexpressing cells, and antioxidant treatment increased MKP3 phosphatase activity, thereby blocking resistance. Furthermore, PD98059 increased the levels of phosphorylated c-Jun NH2-terminal kinase (JNK) in tamoxifen-treated MKP3-overexpressing cells, suggesting an interaction between MKP3 levels, activation of ERK1/2 MAPK, and JNK signaling in human breast cancer cells. MKP3 represents a novel mechanism of resistance, which may be a potential biomarker for the use of ERK1/2 and/or JNK inhibitors in combination with tamoxifen treatment. (Cancer Res 2006; 66(11): 5950-9)
Oncoprotein EWS-FLI1 Activity Is Enhanced by RNA Helicase A
Authors: Toretsky Jeffrey A. , Erkizan Verda , Levenson Amy , Abaan Ogan D. , Parvin Jeffrey D. , Cripe Timothy P. , Rice Anna M. , Lee Sean Bong , Üren Aykut 
Published: June 2006

Abstract
RNA helicase A (RHA), a member of the DEXH box helicase family of proteins, is an integral component of protein complexes that regulate transcription and splicing. The EWS-FLI1 oncoprotein is expressed as a result of the chromosomal translocation t(11;22) that occurs in patients with the Ewing's sarcoma family of tumors (ESFT). Using phage display library screening, we identified an EWS-FLI1 binding peptide containing homology to RHA. ESFT cell lines and patient tumors highly expressed RHA. GST pull-down and ELISA assays showed that EWS-FLI1 specifically bound RHA fragment amino acids 630 to 1020, which contains the peptide region discovered by phage display. Endogenous RHA was identified in a protein complex with EWS-FLI1 in ESFT cell lines. Chromatin immunoprecipitation experiments showed both EWS-FLI1 and RHA bound to EWS-FLI1 target gene promoters. RHA stimulated the transcriptional activity of EWS-FLI1 regulated promoters, including Id2, in ESFT cells. In addition, RHA expression in mouse embryonic fibroblast cells stably transfected with EWS-FLI1 enhanced the anchorage-independent phenotype above that with EWS-FLI1 alone. These results suggest that RHA interacts with EWS-FLI1 as a transcriptional cofactor to enhance its function. (Cancer Res 2006; 66(11): 5574-81)
Cardiac Glycosides Initiate Apo2L/TRAIL-Induced Apoptosis in Non–Small Cell Lung Cancer Cells by Up-regulation of Death Receptors 4 and 5
Authors: Frese Steffen , Frese-Schaper Manuela , Andres Anne-Catherine , Miescher Daniela , Zumkehr Beatrice , Schmid Ralph A. 
Published: June 2006

Abstract
Tumor necrosis factor (TNF)–related apoptosis-inducing ligand (Apo2L/TRAIL) belongs to the TNF family known to transduce their death signals via cell membrane receptors. Because it has been shown that Apo2L/TRAIL induces apoptosis in tumor cells without or little toxicity to normal cells, this cytokine became of special interest for cancer research. Unfortunately, cancer cells are often resistant to Apo2L/TRAIL-induced apoptosis; however, this can be at least partially negotiated by parallel treatment with other substances, such as chemotherapeutic agents. Here, we report that cardiac glycosides, which have been used for the treatment of cardiac failure for many years, sensitize lung cancer cells but not normal human peripheral blood mononuclear cells to Apo2L/TRAIL-induced apoptosis. Sensitization to Apo2L/TRAIL mediated by cardiac glycosides was accompanied by up-regulation of death receptors 4 (DR4) and 5 (DR5) on both RNA and protein levels. The use of small interfering RNA revealed that up-regulation of death receptors is essential for the demonstrated augmentation of apoptosis. Blocking of up-regulation of DR4 and DR5 alone significantly reduced cell death after combined treatment with cardiac glycosides and Apo2L/TRAIL. Combined silencing of DR4 and DR5 abrogated the ability of cardiac glycosides and Apo2L/TRAIL to induce apoptosis in an additive manner. To our knowledge, this is the first demonstration that glycosides up-regulate DR4 and DR5, thereby reverting the resistance of lung cancer cells to Apo2/TRAIL-induced apoptosis. Our data suggest that the combination of Apo2L/TRAIL and cardiac glycosides may be a new interesting anticancer treatment strategy. (Cancer Res 2006; 66(11): 5867-74)
Deletion of the COOH-Terminal Domain of CXC Chemokine Receptor 4 Leads to the Down-regulation of Cell-to-Cell Contact, Enhanced Motility and Proliferation in Breast Carcinoma Cells
Authors: Ueda Yukiko , Neel Nicole F. , Schutyser Evemie , Raman Dayanidhi , Richmond Ann 
Published: June 2006

AbstractThe CXC chemokine receptor 4 (CXCR4) contributes to the metastasis of human breast cancer cells. The CXCR4 COOH-terminal domain (CTD) seems to play a major role in regulating receptor desensitization and down-regulation. We expressed either wild-type CXCR4 (CXCR4-WT) or CTD-truncated CXCR4 (CXCR4-ΔCTD) in MCF-7 human mammary carcinoma cells to determine whether the CTD is involved in CXCR4-modulated proliferation of mammary carcinoma cells. CXCR4-WT-transduced MCF-7 cells (MCF-7/CXCR4-WT cells) do not differ from vector-transduced MCF-7 control cells in morphology or growth rate. However, CXCR4-ΔCTD-transduced MCF-7 cells (MCF-7/CXCR4-ΔCTD cells) exhibit a higher growth rate and altered morphology, potentially indicating an epithelial-to-mesenchymal transition. Furthermore, extracellular signal-regulated kinase (ERK) activation and cell motility are increased in these cells. Ligand induces receptor association with β-arrestin for both CXCR4-WT and CXCR4-ΔCTD in these MCF-7 cells. Overexpressed CXCR4-WT localizes predominantly to the cell surface in unstimulated cells, whereas a significant portion of overexpressed CXCR4-ΔCTD resides intracellularly in recycling endosomes. Analysis with human oligomicroarray, Western blot, and immunohistochemistry showed that E-cadherin and Zonula occludens are down-regulated in MCF-7/CXCR4-ΔCTD cells. The array analysis also indicates that mesenchymal marker proteins and certain growth factor receptors are up-regulated in MCF-7/CXCR4-ΔCTD cells. These observations suggest that (a) the overexpression of CXCR4-ΔCTD leads to a gain-of-function of CXCR4-mediated signaling and (b) the CTD of CXCR4-WT may perform a feedback repressor function in this signaling pathway. These data will contribute to our understanding of how CXCR4-ΔCTD may promote progression of breast tumors to metastatic lesions. (Cancer Res 2006; 66(11): 5665-75)