Economic bioconversion of plant cell wall hydrolysates into fuels and chemicals has been hampered mainly due to the inability of microorganisms to efficiently co-ferment pentose and hexose sugars, especially glucose and xylose, which are the most abundant sugars in cellulosic hydrolysates. Saccharomyces cerevisiae cannot metabolize xylose due to a lack of xylose-metabolizing enzymes. We developed a rapid and efficient xylose-fermenting S. cerevisiae through rational and inverse metabolic engineering strategies, comprising the optimization of a heterologous xylose-assimilating pathway and evolutionary engineering. Strong and balanced expression levels of the XYL1, XYL2, and XYL3 genes constituting the xylose-assimilating pathway increased ethanol yields and the xylose consumption rates from a mixture of glucose and xylose with little xylitol accumulation. The engineered strain, however, still exhibited a long lag time when metabolizing xylose above 10 g/l as a sole carbon source, defined here as xylose toxicity. Through serial-subcultures on xylose, we isolated evolved strains which exhibited a shorter lag time and improved xylose-fermenting capabilities than the parental strain. Genome sequencing of the evolved strains revealed that mutations in PHO13 causing loss of the Pho13p function are associated with the improved phenotypes of the evolved strains. Crude extracts of a PHO13-overexpressing strain showed a higher phosphatase activity on xylulose-5-phosphate (X-5-P), suggesting that the dephosphorylation of X-5-P by Pho13p might generate a futile cycle with xylulokinase overexpression. While xylose consumption rates by the evolved strains improved substantially as compared to the parental strain, xylose metabolism was interrupted by accumulated acetate. Deletion of ALD6 coding for acetaldehyde dehydrogenase not only prevented acetate accumulation, but also enabled complete and efficient fermentation of xylose as well as a mixture of glucose and xylose by the evolved strain. These findings provide direct guidance for developing industrial strains to produce cellulosic fuels and chemicals.
The core protein (HBc) of hepatitis B virus (HBV) has been implicated in the malignant transformation of chronically-infected hepatocytes and displays pleiotropic functions, including RNA- and DNA-binding activities. However, the mechanism by which HBc interacts with the human genome to exert effects on hepatocyte function remains unknown. This study investigated the distribution of HBc binding to promoters in the human genome and evaluated its effects on the related genes’ expression.
Whole-genome chromatin immunoprecipitation microarray (ChIP-on-chip) analysis was used to identify HBc-bound human gene promoters. Gene Ontology and pathway analyses were performed on related genes. The quantitative polymerase chain reaction assay was used to verify ChIP-on-chip results. Five novel genes were selected for luciferase reporter assay evaluation to assess the influence of HBc promoter binding. The HBc antibody immunoprecipitated approximately 3100 human gene promoters. Among these, 1993 are associated with known biological processes, and 2208 regulate genes with defined molecular functions. In total, 1286 of the related genes mediate primary metabolic processes, and 1398 encode proteins with binding activity. Sixty-four of the promoters regulate genes related to the mitogen-activated protein kinase (MAPK) pathways, and 41 regulate Wnt/beta-catenin pathway genes. The reporter gene assay indicated that HBc binding up-regulates proto-oncogene tyrosine-protein kinase (SRC), type 1 insulin-like growth factor receptor (IGF1R), and neurotrophic tyrosine kinase receptor 2 (NTRK2), and down-regulates v-Ha-ras Harvey rat sarcoma viral oncogene (HRAS).
HBc has the ability to bind a large number of human gene promoters, and can disrupt normal host gene expression. Manipulation of the transcriptional profile in HBV-infected hepatocytes may represent a key pathogenic mechanism of HBV infection.
Hepatitis B virus; Hepatitis B core protein; Chromatin immunoprecipitation microarray; ChIP-on-chip; Gene expression; DNA-protein interaction
Dapper homolog 1 (DACT1) is a disheveled partner in the planar cell polarity pathway. By using genome-wide promoter methylation screening, dapper homolog 1 (DACT1) was found to be frequently methylated in gastric cancer. We aim to clarify its epigenetic inactivation, biological function and clinical implication in gastric cancer. We demonstrated that DACT1 was silenced in 7 of 10 gastric cancer cell lines and in primary gastric cancers. Transcriptional gene silence of DACT1 was mainly regulated by promoter hypermethylation. Ectopic expression of DACT1 in silenced gastric cancer cell lines (AGS, BGC823 and MGC803) by stable transfection suppressed colony formation (P < 0.001), induced cell apoptosis (P < 0.01) and retarded tumorigenesis in nude mice (P < 0.001). The tumor suppressive effect of DACT1 was further confirmed by loss of DACT1 function experiment. The proapoptotic and antiproliferative effect by DACT1 was associated with inhibition of nuclear factor (NF)-κB activation and its downstream factors, including B-cell CLL/lymphoma-2, Bcl-X, interleukin-8 and tumor necrosis factor-α. Moreover, promoter methylation of DACT1 was detected in 29.3% (60/205) of primary gastric tumors. DACT1 methylation was significantly associated with tumor metastasis (P < 0.05), invasion (P < 0.05) and advanced tumor stage (P < 0.0005). These findings provided insight into the role of DACT1 as a novel functional tumor suppressor in gastric cancer through inhibiting NF-κB signaling pathway. Promoter methylation of DACT1 is associated with tumor aggressiveness.
3-D optical coherence tomography (OCT) has been extensively investigated as a potential screening and/or surveillance tool for Barrett’s esophagus (BE). Understanding and correcting motion artifact may improve image interpretation. In this work, the motion trace was analyzed to show the physiological origin (respiration and heart beat) of the artifacts. Results showed that increasing balloon pressure did not sufficiently suppress the physiological motion artifact. An automated registration algorithm was designed to correct such artifacts. The performance of the algorithm was evaluated in images of normal porcine esophagus and demonstrated in images of BE in human patients.
(110.4500) Optical coherence tomography; (170.2150) Endoscopic imaging; (100.3010) Image reconstruction techniques
Der f 7 is the group 7 allergen from the dust mite Dermatophagoides farinae, homologous to the major allergen Der p 7 from D. pteronyssinus. Monoclonal antibody that bind to residues Leu48 and Phe50 was found to inhibit IgE binding to residue Asp159, which is important for the cross-reactivity between Der f 7 and Der p 7.
Here, we report the crystal structure of Der f 7 that shows an elongated and curved molecule consisting of two anti-parallel β-sheets – one 4-stranded and the other 5-stranded – that wrap around a long C-terminal helix. The overall fold of Der f 7 is similar to Der p 7 but key difference was found in the β1–β2 loop region. In Der f 7, Leu48 and Phe50 are in close proximity to Asp159, explaining why monoclonal antibody binding to Leu48 and Phe50 can inhibit IgE binding to Asp159. Both Der f 7 and Der p 7 bind weakly to polymyxin B via a similar binding site that is formed by the N-terminal helix, the 4-stranded β-sheet and the C-terminal helix. The thermal stability of Der f 7 is significantly lower than that of Der p 7, and the stabilities of both allergens are highly depend on pH.
Der f 7 is homologous to Der p 7 in terms of the amino acid sequence and overall 3D structure but with significant differences in the region proximal to the IgE epitope and in thermal stability. The crystal structure of Der f 7 provides a basis for studying the function and allergenicity of this group of allergens.
To verify the ability to identify the layered structures of ureteral wall and to image a segment of ureter in three dimensions with a high speed endoscopic optical coherence tomography (EOCT).
We imaged a porcine ureter ex vivo using a spectral domain EOCT with an specially designed circumferential scanning fiber catheter. The images were correlated with the histology to identify corresponding structures. Three-dimensional images and en face images at different depths from the luminal surface were reconstructed from the multiple cross-sectional images to visualize the layered structure of a segment of the ureter from different perspectives.
EOCT images can clearly reveal all layers of the ureteral wall as shown in the histological images. Especially, with the specially designed fiber catheter, the light beam was well centered during the rotation and pull back, which allowed constant acquisition of high fidelity images and unambiguous identification of the smooth muscle layers in all images. With high speed EOCT, a segment of ureter (20 mm) can be imaged in less than 90 seconds at a high resolution.
With its ability to visualize all layers of the ureteral wall, EOCT imaging offers the potential to stage urothelial cancers that have infiltrated the muscular wall (stage T2). This information will be complimentary to the diagnostic information obtained through ureteroscopic biopsy and CT urogram.
Optical coherence tomography; Ureteral Cancer; Three dimensions; Endoscopic
Stathmin1 (STMN1) is a candidate oncoprotein and prognosis marker in several kinds of cancers. This study was aimed to analyze its expression and biological functions in gastric cancer. The expression of STMN1 was evaluated by qRT-PCR, western blot and immunohistochemistry. The biological function of STMN1 was determined by MTT proliferation assays, monolayer colony formation and cell invasion assays using small interference RNA technique in gastric cancer cell lines. We also explored the regulation of STMN1 expression by microRNA-223. STMN1 was upregulated in gastric cancer cell lines and primary gastric adenocarcinomas. STMN1-positive tumors were more likely to be found in old age group and associated with p53 nuclear expression. In diffuse type gastric adenocarcinomas, STMN1 expression was correlated with age (p = 0.043), T stage (p = 0.004) and lymph node metastasis (p = 0.046). Expression of STMN1 in diffuse type gastric adenocarcinoma was associated with poor disease specific survival by univariate analysis (p = 0.01). STMN1 knockdown in AGS and MKN7 cell lines suppressed proliferation (p<0.001), reduced monolayer colony formation (p<0.001), inhibited cell invasion and migration ability (p<0.001) and induced G1 phase arrest. siSTMN1 could also suppress cell growth in vivo (p<0. 01). We finally confirmed that STMN1 is a putative downstream target of miR-223 in gastric cancer. Our findings supported an oncogenic role of STMN1 in gastric cancer. STMN1 might serve as a prognostic marker and a potential therapeutic target for gastric cancer.
Fourier-domain optical coherence tomography (OCT) and balloon-based catheters have furthered the potential of OCT as a real-time surveillance tool for Barrett’s esophagus (BE). However, a balloon catheter, which expands the esophagus and centers the catheter, applies direct pressure on the esophagus. This may affect the tissue appearance and the ability to detect dysplasia in BE. To study this effect, we propose a double-balloon catheter to allow imaging with and without balloon-tissue contact. A system design based on a spectral-domain OCT platform is reported and validated by acquisition of high quality, volumetric images of swine esophagus in vivo.
(110.4500) Optical Coherence Tomography; (170.2150) Endoscopic imaging
Objective. To investigate whether ω-3 fatty acid could stimulate gastrointestinal motility after abdominal operation. Method. Wistar rats were randomly divided into 3 group (normal saline group, intralipid group, and ω-3 fatty acid group, n = 18/group) after partial caecectomy and gastrostomosis, each group was divided into 3 groups (POD1, POD3, and POD6, n = 6/group). Serum gastrin (GAS), motilin (MTL), interleukin-1 (IL-1), interleukin-6 (IL-6), tissue necrosis factor-α (TNF-α), cyclooxygenase-2 (COX-2), gastric emptying rate, and small bowel propulsion rate were measured. Results. On POD 3, gastric emptying rate and small bowel propulsion rate in ω-3 fatty acid group were higher than those in normal saline group and intralipid group. Serum GAS and MTL levels in ω-3 fatty acid group were higher than those in normal saline group, but serum IL-1, IL-6, TNF-α, and COX-2 levels were lower than those in normal saline group and intralipid group. Conclusion. ω-3 fatty acid could accelerate the recovery of gastrointestinal mobility after abdominal operation in rats, mainly by relieving postoperative inflammation.
The reaction of cobalt(II) sulfate and 2-aminopyrazine affords the title salt, [Co(H2O)6][Co(C4H5N3)2(H2O)4](SO4)2·2H2O. The metal atoms in the tetraaqua-coordinated and hexaaqua-coordinated complex cations lie on centers of inversion in slightly distorted octahedral geometries. The cations, anions and solvent water molecules are linked by O—H⋯O, O—H⋯N and N—H⋯O hydrogen bonds into a three-dimensional network.
The CoII atom in the title complex, [CoCl2(C4H5N3)4], exists in an all-trans Cl2N4Co octahedral geometry. The CoII atom lies on a special position of 2 site symmetry. Adjacent molecules are linked by N—H⋯N and N—H⋯Cl hydrogen bonds into a three-dimensional network.
Hemotrophic mycoplasmas; hemoplasmas; China; bacteria; letter