bluuebunny/crossref_metadata_2025_split huggingface dataset:
Serine-Rich Repeat Proteins and Pili Promote Streptococcus agalactiae Colonization of the Vaginal Tract
Authors: Sheen Tamsin R. , Jimenez Alyssa , Wang Nai-Yu , Banerjee Anirban , van Sorge Nina M. , Doran Kelly S. 
Published: October 2011

ABSTRACTStreptococcus agalactiae(group B streptococcus [GBS]) is a Gram-positive bacterium found in the female rectovaginal tract and is capable of producing severe disease in susceptible hosts, including newborns and pregnant women. The vaginal tract is considered a major reservoir for GBS, and maternal vaginal colonization poses a significant risk to the newborn; however, little is known about the specific bacterial factors that promote GBS colonization and persistence in the female reproductive tract. We have developedin vitromodels of GBS interaction with the human female cervicovaginal tract using human vaginal and cervical epithelial cell lines. Analysis of isogenic mutant GBS strains deficient in cell surface organelles such as pili and serine-rich repeat (Srr) proteins shows that these factors contribute to host cell attachment. As Srr proteins are heavily glycosylated, we confirmed that carbohydrate moieties contribute to the effective interaction of Srr-1 with vaginal epithelial cells. Antibody inhibition assays identified keratin 4 as a possible host receptor for Srr-1. Our findings were further substantiated in anin vivomouse model of GBS vaginal colonization, where mice inoculated with an Srr-1-deficient mutant exhibited decreased GBS vaginal persistence compared to those inoculated with the wild-type (WT) parental strain. Furthermore, competition experiments in mice showed that WT GBS exhibited a significant survival advantage over the ΔpilAor Δsrr-1mutant in the vaginal tract. Our results suggest that these GBS surface proteins contribute to vaginal colonization and may offer new insights into the mechanisms of vaginal niche establishment.
Deletion of the Aconitase Gene in Corynebacterium glutamicum Causes Strong Selection Pressure for Secondary Mutations Inactivating Citrate Synthase
Authors: Baumgart Meike , Mustafi Nurije , Krug Andreas , Bott Michael 
Published: October 2011

ABSTRACT

The aconitase gene
acn
of
Corynebacterium glutamicum
is regulated by four transcriptional regulators, indicating that the synthesis of this enzyme is carefully controlled. To understand the causes for this elaborate regulation, the properties of the Δ
acn
-1 deletion mutant were analyzed in detail. The mutant was glutamate auxotrophic in glucose minimal medium, showed a strong growth defect, and secreted large amounts of acetate. None of these phenotypes could be complemented by plasmid-encoded aconitase, suggesting the presence of a secondary mutation. In fact, a point mutation within the
gltA
gene encoding citrate synthase was identified that caused the instability of the protein and an almost complete lack of its enzymatic activity. Subsequently, 27 further, independent Δ
acn
clones were isolated, and 15 of them were found to contain distinct mutations in
gltA
, causing the loss of citrate synthase activity. A similar result was observed for mutants lacking the isocitrate dehydrogenase gene
icd
. In this case, 8 of 24 Δ
icd
clones contained additional mutations in
gltA
. Indirect evidence was obtained that elevated intracellular citrate concentrations could be the cause of this selection pressure. Accordingly, the careful control of aconitase synthesis might have evolved due to the necessity to avoid inhibitory cytoplasmic citrate levels on the one hand and to prevent the excessive synthesis of an oxygen-sensitive protein requiring both iron and sulfur on the other hand.
Mycobacterium smegmatis RoxY Is a Repressor ofoxySand Contributes to Resistance to Oxidative Stress and Bactericidal Ubiquitin-Derived Peptides
Authors: Daugherty Aaron , Powers Katelyn M. , Standley Melissa S. , Kim Cathy S. , Purdy Georgiana E. 
Published: October 2011

ABSTRACTThe mycobactericidal properties of macrophages include the generation of reactive oxygen intermediates and the delivery of bacteria to a hydrolytic lysosome enriched in bactericidal ubiquitin-derived peptides (Ub-peptides). To better understand the interactions of ubiquitin-derived peptides with mycobacteria and identify putative mycobacterial intrinsic resistance mechanisms, we screened for transposon mutants with increased susceptibility to the bactericidal Ub-peptide Ub2. We isolated 27Mycobacterium smegmatismutants that were hypersusceptible to Ub2. Two mutants were isolated that possessed mutations in themsmeg_0166gene, which encodes a transcriptional regulator. Themsmeg_0166mutants were also hypersusceptible to other host antimicrobial peptides and oxidative stress. In characterizingmsmeg_0166, we found that it encodes arepressor ofoxyS, and therefore we have renamed the generoxY. We demonstrate that RoxY and OxyS contribute toM. smegmatisresistance to oxidative stress. AnahpDtransposon mutant was also isolated in our screen for Ub-peptide hypersusceptibility. Overexpression ofoxySinM. smegmatisreduced transcription of theahpCDgenes, which encode a peroxide detoxification system. Our data indicate that RoxY, OxyS, and AhpD play a role in the mycobacterial oxidative stress response and are important for resistance to host antimicrobial peptides.
Deletion of One Nucleotide within the Homonucleotide Tract Present in the
hsdS
Gene Alters the DNA Sequence Specificity of Type I Restriction-Modification System NgoAV
Authors: Adamczyk-Poplawska Monika , Lower Michal , Piekarowicz Andrzej 
Published: October 2011

ABSTRACT

As a result of a frameshift mutation, the
hsdS
locus of the NgoAV type IC restriction and modification (RM) system comprises two genes,
hsdS
NgoAV1
and
hsdS
NgoAV2
. The specificity subunit, HsdS
NgoAV
, the product of the
hsdS
NgoAV1
gene, is a naturally truncated form of an archetypal specificity subunit (208 N-terminal amino acids instead of 410). The presence of a homonucleotide tract of seven guanines (poly[G]) at the 3′ end of the
hsdS
NgoAV1
gene makes the NgoAV system a strong candidate for phase variation, i.e., stochastic addition or reduction in the guanine number. We have constructed mutants with 6 guanines instead of 7 and demonstrated that the deletion of a single nucleotide within the 3′ end of the
hsdS
NgoAV1
gene restored the fusion between the
hsdS
NgoAV1
and
hsdS
NgoAV2
genes. We have demonstrated that such a contraction of the homonucleotide tract may occur
in vivo
: in a
Neisseria gonorrhoeae
population, a minor subpopulation of cells appeared to have only 6 guanines at the 3′ end of the
hsdS
NgoAV1
gene.
Escherichia coli
cells carrying the fused gene and expressing the NgoAVΔ RM system were able to restrict λ phage at a level comparable to that for the wild-type NgoAV system. NgoAV recognizes the quasipalindromic interrupted sequence 5′-GCA(N
8
)TGC-3′ and methylates both strands. NgoAVΔ recognizes DNA sequences 5′-GCA(N
7
)GTCA-3′ and 5′-GCA(N
7
)CTCA-3′, although the latter sequence is methylated only on the complementary strand within the 5′-CTCA-3′ region of the second recognition target sequence.
Fine-Tuning Control ofphoBRExpression in Vibrio cholerae by Binding of PhoB to Multiple Pho Boxes
Authors: Diniz Michelle Menezes Passos , Goulart Carolina Lage , Barbosa Livia Carvalho , Farache Júlia , Lery Letícia Miranda Santos , Pacheco Ana Beatriz Furlanetto , Bisch Paulo Mascarello , von Krüger Wanda Maria de Almeida 
Published: October 2011

ABSTRACTThe control ofVibrio choleraephoBRexpression by PhoB involves its binding to Pho boxes at −35 (box 1), −60 (box 2), and −80 (box 3) from the putativephoBtranslation start site. These loci were located in the sense (box 1) and antisense (boxes 2 and 3) strands of thephoBRregulatory region, and PhoB binds to these individual boxes with distinct affinities. Fusions of sequences containing different combinations of these boxes upstream of thelacZreporter in a plasmid demonstrated that only those carrying boxes 1, 2, and 3, or 1 alone, activated transcription under inorganic phosphate (Pi) limitation. When a fragment, including only boxes 1 and 2, was fused tolacZ, expression was no longer induced by low Pi, suggesting a repressive role for PhoB∼box2 (PhoB bound to box 2) over the transcriptional activity induced by PhoB∼box1. The similarity betweenlacZexpression levels from promoter fragments containing the three boxes or box 1 alone showed that PhoB∼box3 eliminated the repressive effect imposed by PhoB∼box2 onphoBRtranscription. Complementation assays with aphoBR-containing plasmid demonstrated that the 234-bp promoter fragment carrying the three boxes is absolutely required for operon expression inVibrio choleraeΔphoBRcells. This was observed under Piabundance, whenphoBRwas expressed at a basal level and, also in low Piconditions, when Pho regulon genes were fully expressed. Thus, under Pilimitation, PhoB exerts dual regulatory functions by binding sequentially distinct Pho boxes to enable the fine-tuning and precise control ofphoBRexpression inV. choleraecells.
Organization and Evolution of the
cotG
and
cotH
Genes of Bacillus subtilis
Authors: Giglio Rosa , Fani Renato , Isticato Rachele , De Felice Maurilio , Ricca Ezio , Baccigalupi Loredana 
Published: October 2011

ABSTRACT

The
cotG
and
cotH
genes of
Bacillus subtilis
encode two previously characterized spore coat proteins. The two genes are adjacent on the chromosome and divergently transcribed by σ
K
, a sporulation-specific σ factor of the RNA polymerase. We report evidence that the
cotH
promoter maps 812 bp upstream of the beginning of its coding region and that the divergent
cotG
gene is entirely contained between the promoter and the coding part of
cotH
. A bioinformatic analysis of all entirely sequenced prokaryotic genomes showed that such chromosomal organization is not common in spore-forming bacilli. Indeed, CotG is present only in
B. subtilis
,
B. amyloliquefaciens
, and
B. atrophaeus
and in two
Geobacillus
strains. When present,
cotG
always encodes a modular protein composed of tandem repeats and is always close to but divergently transcribed with respect to
cotH
. Bioinformatic and phylogenic data suggest that such genomic organizations have a common evolutionary origin and that the modular structure of the extant
cotG
genes is the outcome of multiple rounds of gene elongation events of an ancestral minigene.
Hfq Virulence Regulation in Enterohemorrhagic Escherichia coli O157:H7 Strain 86-24
Authors: Kendall Melissa M. , Gruber Charley C. , Rasko David A. , Hughes David T. , Sperandio Vanessa 
Published: October 2011

ABSTRACT

Enterohemorrhagic
Escherichia coli
O157:H7 (EHEC) causes bloody diarrhea and hemolytic-uremic syndrome. EHEC encodes the sRNA chaperone Hfq, which is important in posttranscriptional regulation. In EHEC strain EDL933, Hfq acts as a negative regulator of the locus of enterocyte effacement (LEE), which encodes most of the proteins involved in type III secretion and attaching and effacing (AE) lesions. Here, we deleted
hfq
in the EHEC strain 86-24 and compared global transcription profiles of the
hfq
mutant and wild-type (WT) strains in exponential growth phase. Deletion of
hfq
affected transcription of genes common to nonpathogenic and pathogenic strains of
E. coli
as well as pathogen-specific genes. Downregulated genes in the
hfq
mutant included
ler
, the transcriptional activator of all the LEE genes, as well as genes encoded in the
LEE2
to
-5
operons. Decreased expression of the LEE genes in the
hfq
mutant occurred at middle, late, and stationary growth phases. We also confirmed decreased regulation of the LEE genes by examining the proteins secreted and AE lesion formation by the
hfq
mutant and WT strains. Deletion of
hfq
also caused decreased expression of the two-component system
qseBC
, which is involved in interkingdom signaling and virulence gene regulation in EHEC, as well as an increase in expression of
stx
2AB
, which encodes the deadly Shiga toxin. Altogether, these data indicate that Hfq plays a regulatory role in EHEC 86-24 that is different from what has been reported for EHEC strain EDL933 and that the role of Hfq in EHEC virulence regulation extends beyond the LEE.
The Same Periplasmic ExbD Residues Mediate
In Vivo
Interactions between ExbD Homodimers and ExbD-TonB Heterodimers
Authors: Ollis Anne A. , Postle Kathleen 
Published: October 2011

ABSTRACT

The TonB system couples cytoplasmic membrane proton motive force to TonB-gated outer membrane transporters for active transport of nutrients into the periplasm. In
Escherichia coli
, cytoplasmic membrane proteins ExbB and ExbD promote conformational changes in TonB, which transmits this energy to the transporters. The only known energy-dependent interaction occurs between the periplasmic domains of TonB and ExbD. This study identified sites of
in vivo
homodimeric interactions within ExbD periplasmic domain residues 92 to 121. ExbD was active as a homodimer (ExbD
2
) but not through all Cys substitution sites, suggesting the existence of conformationally dynamic regions in the ExbD periplasmic domain. A subset of homodimeric interactions could not be modeled on the nuclear magnetic resonance (NMR) structure without significant distortion. Most importantly, the majority of ExbD Cys substitutions that mediated homodimer formation also mediated ExbD-TonB heterodimer formation with TonB A150C. Consistent with the implied competition, ExbD homodimer formation increased in the absence of TonB. Although ExbD D25 was not required for their formation, ExbD dimers interacted
in vivo
with ExbB. ExbD-TonB interactions required ExbD transmembrane domain residue D25. These results suggested a model where ExbD
2
assembled with ExbB undergoes a transmembrane domain-dependent transition and exchanges partners in localized homodimeric interfaces to form an ExbD
2
-TonB heterotrimer. The findings here were also consistent with our previous hypothesis that ExbD guides the conformation of the TonB periplasmic domain, which itself is conformationally dynamic.
Computed tomographic examination of South American sea lions (Otaria flavescens) with suspected Mycobacterium pinnipedii infection
Authors: Jurczynski K. , Scharpegge J. , Ley‐Zaporozhan J. , Ley S. , Cracknell J. , Lyashchenko K. , Greenwald R. , Schenk J. P. 
Published: October 2011

Ten South American sea lions (Otaria flavescens) were presented for clinical evaluation and diagnosis of tuberculosis following known exposure to Mycobacterium pinnipedii. CT was used to determine whether foci of calcification in mediastinal lymph nodes, typically associated with pinniped tuberculosis, could be detected and whether CT was a useful diagnostic modality, in conjunction with other tests, for the diagnosis of tuberculosis in this species. Blood was collected from the caudal gluteal vein of each animal for serological testing using commercially available serological tests (ElephantTB STAT‐PAK and DPP Vet; Chembio Diagnostic Systems) and a multiantigen print immunoassay (MAPIA), carried out at Chembio to verify the in‐house kits. In four of nine animals that underwent CT scanning, lesions consistent with pinniped tuberculosis were apparent and these were confirmed at subsequent postmortem examination. The five remaining animals did not show any abnormalities on CT, with three being negative on serological tests, which were considered to be normal and potentially used as reference images for healthy sea lions. One animal could not be CT scanned due to its large size and weight (510 kg).
Multiple Stress Signals Activate Mutant p53 In Vivo
Authors: Suh Young-Ah , Post Sean M. , Elizondo-Fraire Ana C. , Maccio Daniela R. , Jackson James G. , El-Naggar Adel K. , Van Pelt Carolyn , Terzian Tamara , Lozano Guillermina 
Published: October 2011

Abstract
p53 levels are tightly regulated in normal cells, and thus, the wild-type p53 protein is nearly undetectable until stimulated through a variety of stresses. In response to stress, p53 is released from its negative regulators, mainly murine double minute 2 (Mdm2), allowing p53 to be stabilized to activate cell-cycle arrest, senescence, and apoptosis programs. Many of the upstream signals that regulate wild-type p53 are known; however, limited information for the regulation of mutant p53 exists. Previously, we showed that wild-type and mutant p53R172H are regulated in a similar manner in the absence of Mdm2 or p16. In addition, this stabilization of mutant p53 is responsible for the gain-of-function metastatic phenotype observed in the mouse. In this report, we examined the role of oncogenes, DNA damage, and reactive oxygen species, signals that stabilize wild-type p53, on the stabilization of mutant p53 in vivo and the consequences of this expression on tumor formation and survival. These factors stabilized mutant p53 protein which oftentimes contributed to exacerbated tumor phenotypes. These findings, coupled with the fact that patients carry p53 mutations without stabilization of p53, suggest that personalized therapeutic schemes may be needed for individual patients depending on their p53 status. Cancer Res; 71(23); 7168–75. ©2011 AACR.
Volumetric and Angiogenic Evaluation of Antitumor Effects with Acoustic Liposome and High-Frequency Ultrasound
Authors: Kodama Tetsuya , Tomita Noriko , Yagishita Yoko , Horie Sachiko , Funamoto Kenichi , Hayase Toshiyuki , Sakamoto Maya , Mori Shiro 
Published: October 2011

Abstract
Acoustic liposomes (AL) have their inherent echogenicity and can add functionality in serving as drug carriers with tissue specificity. Nonuniform vascular structures and vascular branches/bends are evaluated by imaging the intravascular movement locus of ALs with high-frequency ultrasound (HF-US) imaging. However, the evaluation of antitumor effects on angiogenesis by ALs and HF-US imaging has not been reported. Here, we show that the combination of ALs and an HF-US imaging system is capable of noninvasively evaluating antitumor volumetric and angiogenic effects in preclinical mouse models of various cancers. In this study, the antitumor effects of cisplatin on tumor growth and angiogenesis in mice bearing two different types of tumor cells were assessed. By tracking each AL flowing in the vessel and transferring the images to personal computers, microvessel structures were mapped and reconstructed using the color difference based on SD method. The antitumor effects were confirmed with an in vivo bioluminescence imaging system and immunohistochemical analysis. Our results show that cisplatin inhibits tumor growth by decreasing intratumoral vessel area but does not affect the angiogenesis ratio in the tumor. The vascular occupancy in the outer region of the tumor was larger than that in the inner region; however, both occupancies were similar to those of the control tumor. We propose that this method of mapping microvessels with ALs and an HF-US system can serve as a new molecular imaging method for the assessment of angiogenesis and can be applied to evaluate the antitumor effects by various therapeutic agents. Cancer Res; 71(22); 6957–64. ©2011 AACR.
Interaction of HIF and USF Signaling Pathways in Human Genes Flanked by Hypoxia-Response Elements and E-box Palindromes
Authors: Hu Junmin , Stiehl Daniel P. , Setzer Claudia , Wichmann Daniela , Shinde Dheeraj A. , Rehrauer Hubert , Hradecky Pavel , Gassmann Max , Gorr Thomas A. 
Published: October 2011

Abstract
Rampant activity of the hypoxia-inducible factor (HIF)-1 in cancer is frequently associated with the malignant progression into a harder-to-treat, increasingly aggressive phenotype. Clearly, anti-HIF strategies in cancer cells are of considerable clinical interest. One way to fine-tune, or inhibit, HIF's transcriptional outflow independently of hydroxylase activities could be through competing transcription factors. A CACGTG-binding activity in human hepatoma cells was previously found to restrict HIF's access to hypoxia response cis-elements (HRE) in a Daphnia globin gene promoter construct (phb2). The CACGTG factor, and its impact on hypoxia-responsive human genes, was analyzed in this study by genome-wide computational scans as well as gene-specific quantitative PCR, reporter and DNA-binding assays in hepatoma (Hep3B), cervical carcinoma (HeLa), and breast carcinoma (MCF7) cells. Among six basic helix-loop-helix transcription factors known to target CACGTG palindromes, we identified upstream stimulatory factor (USF)-1/2 as predominant phb2 CACGTG constituents in Hep3B, HeLa, and MCF7 cells. Human genes with adjacent or overlapping HRE and CACGTG motifs included with lactate dehydrogenase A (LDHA) and Bcl-2/E1B 19 kDa interacting protein 3 (BNIP3) hypoxia-induced HIF-1 targets. Parallel recruitment of HIF-1α and USF1/2a to the respective promoter chromatin was verified for all cell lines investigated. Mutual complementing (LDHA) or moderating (BNIP3) cross-talk was seen upon overexpression or silencing of HIF-1α and USF1/2a. Distinct (LDHA) or overlapping (BNIP3) promoter-binding sites for HIF-1 and USFs were subsequently characterized. We propose that, depending on abundance or activity of its protein constituents, O2-independent USF signaling can function to fine-tune or interfere with HIF-mediated transcription in cancer cells. Mol Cancer Res; 9(11); 1520–36. ©2011 AACR.
αB-Crystallin, an Effector of Unfolded Protein Response, Confers Anti-VEGF Resistance to Breast Cancer via Maintenance of Intracrine VEGF in Endothelial Cells
Authors: Ruan Qing , Han Song , Jiang Wen G. , Boulton Michael E. , Chen Zhi J. , Law Brian K. , Cai Jun 
Published: October 2011

Abstract
Effective inhibition of angiogenesis targeting the tumor endothelial cells requires identification of key cellular and molecular mechanisms associated with survival of vasculatures within the tumor microenvironment. Intracellular autocrine (intracrine) VEGF production by endothelial cells plays a critical role on the vasculature homeostasis. In vitro breast cancer cell–stimulated activation of the unfolded protein response (UPR) of the endothelial cells contributes to maintenance of the intracrine VEGF levels in the endothelial cells through the upregulation of a previous undescribed downstream effector- αB-crystallin (CRYAB). siRNA-mediated knockdown of two major UPR proteins—inositol requiring kinase 1 and ATF6, led to attenuated CRYAB expression of the endothelial cells. Finally, inhibition of CRYAB blocked the breast cancer cell–stimulated increase in the endogenous VEGF levels of the endothelial cells. A VEGF limited proteolysis assay further revealed that CRYAB protected VEGF for proteolytic degradation. Here, we report that the molecular chaperone-CRYAB was significantly increased and colocalized with tumor vessels in a breast cancer xenograft. Specifically, neutralization of VEGF induced higher levels of CRYAB expression in the endothelial cells cocultured with MDA-MB-231 or the breast cancer xenograft with a significant survival benefit. However, knockdown of CRYAB had a greater inhibitory effect on endothelial survival. These findings underscore the importance of defining a role for intracrine VEGF signaling in sustaining aberrant tumor angiogenesis and strongly implicate UPR/CRYAB as dichotomous parts of a crucial regulation pathway for maintaining intracrine VEGF signaling. Mol Cancer Res; 9(12); 1632–43. ©2011 AACR.