Min-Jen Tseng

Purification and characterization of two cellulase free xylanases from an alkaliphilic Bacillus firmus

Two xylanases from Bacillus firmus were purified to homogeneity by gel filtration and ion-exchange chromatography. These enzymes have molecular weights of 45 kDa and 23 kDa, respectively, and both show enzymatic activity over the pH range of 5.0–11.0 at 37°C. These enzymes hydrolyzed xylan from birchwood to release mainly the products of xylose, xylotriose and xylohexose, thus indicating that the xylanases act preferentially toward the internal glycosidic bonds of xylo-oligosaccharides. However, the two xylanases show different modes of action, and a combination of both is likely to lead to concerted degradation of xylan down to the mono- and disaccharides.

Biomic study of human myeloid leukemia cells differentiation to macrophages using DNA array, proteomic, and bioinformatic analytical methods.

A biomic approach by integrating three independent methods, DNA microarray, proteomics and bioinformatics, is used to study the differentiation of human myeloid leukemia cell line HL‐60 into macrophages when induced by 12‐O‐tetradecanoyl‐phorbol‐13‐acetate (TPA). Analysis of gene expression changes at the RNA level using cDNA against an array of 6033 human genes showed that 5950 (98.6%) of the genes were expressed in the HL‐60 cells. A total of 624 genes (10.5%) were found to be regulated during HL‐60 cell differentiation. Most of these genes have not been previously associated with HL‐60 cells and include genes encoded for secreted proteins as well as genes involved in cell adhesion, signaling transduction, and metabolism. Protein analysis using two‐dimensional gel electrophoresis showed a total of 682 distinct protein spots; 136 spots (19.9%) exhibited quantitative changes between HL‐60 control and macrophages. These differentially expressed proteins were identified by mass spectrometry. We developed a bioinformatics program, the Bulk Gene Search System (BGSS, http://www.sinica.edu.tw:8900/perl/genequery.pl) to search for the functions of genes and proteins identified by cDNA microarrays and proteomics. The identified regulated proteins and genes were classified into seven groups according to subcellular locations and functions. This powerful holistic biomic approach using cDNA microarray, proteomics coupled to bioinformatics can provide in‐depth information on the impact and importance of the regulated genes and proteins for HL‐60 differentiation.

Adenovirus-mediated gene transfer of RasN17 inhibits specific CCK actions on pancreatic acinar cells

CCK stimulates pleiotrophic responses in pancreatic acinar cells; however, the intracellular signaling pathways involved are not well understood. To evaluate the role of the ras gene product in CCK actions, a strategy involving in vitro adenoviral-mediated gene delivery of a dominant-negative mutant Ras (RasN17) was utilized. Isolated acini were infected with various titers of either a control adenovirus or an adenoviral construct expressing RasN17 for 24 h before being treated with CCK. Titer-dependent expression of RasN17 in the acini was confirmed by Western blotting. Infection with control adenovirus [106-109plaque-forming units/mg acinar protein (multiplicity of infection of ∼1-1,000)] had no effect on CCK stimulation of acinar cell amylase release, extracellular-regulated kinase (ERK) or c-Jun kinase (JNK) kinases, or DNA synthesis. In contrast, infection with adenovirus bearing ras N17 increased basal amylase release, inhibited CCK-mediated JNK activation, had no effect on CCK activation of ERK, and inhibited DNA synthesis. These data demonstrate important roles for Ras in specific actions of CCK on pancreatic acinar function.

Distinct cytoplasmic domains of the growth hormone receptor are required for glucocorticoid- and phorbol ester-induced decreases in growth hormone (GH) binding. These domains are different from that reported for GH-induced receptor internalization

Glucocorticoids inhibit growth in children and antagonize the growth-promoting action of GH in peripheral tissues. Recently, they have been shown to decrease GH binding. In this study we examine the molecular mechanisms by which the glucocorticoid dexamethasone (DEX) and the phorbol ester phorbol myristate acetate (PMA) decrease cellular GH binding. In 3T3-F442A fibroblasts, DEX and PMA decrease the number of GH receptors (GHRs) capable of binding GH by 50% (t1/2 = 6 h) and 70% (t1/2 = 15 min), respectively. Neither appear to decrease the total number of cellular GHR. Rather, they appear to redistribute GHRs away from the plasma membrane or inactivate GHRs on the membrane such that they cannot bind GH. DEX and PMA also decrease GH-induced tyrosyl phosphorylation of GHR and JAK2 with a magnitude and time course correlating with that of inhibition of GH binding. DEX- and PMA-induced reductions of GH binding are also observed in a Chinese hamster ovary (CHO) cell line stably transfected with a rat liver GHR cDNA, further arguing that DEX and PMA act post-translationally on GHR. Using mutant GHRs stably expressed in CHO cells, amino acids 455-506 and tyrosines 333 and/or 338 of GHR were shown to be required for maximal DEX-induced inhibition of GH binding. DEX decreased GH binding to a GHR mutant F346A, which is reported to be deficient in ligand-induced internalization, suggesting that DEX decreases GH binding by a mechanism distinct from that of ligand-induced GHR internalization. PMA reduced GH binding to CHO cells expressing all GHR mutants tested. However, deletion of the C-terminal 132 amino acids decreased this effect, suggesting that at least one component of PMA action on GHR requires amino acids 507-638. These data suggest that distinct pathways mediate the effects of GH, DEX, and PMA on GHR number in the plasma membrane.

Nuclear βII-Tubulin Associates with the Activated Notch Receptor to Modulate Notch Signaling

The Notch signal pathway plays important roles in proliferation, apoptosis, and differentiation. Abnormalities in Notch signaling are linked to many human diseases. After ligand binding, Notch signaling is activated through the cleavage of Notch receptors to release and translocate the Notch intracellular domain into the nucleus. The Notch1 receptor intracellular domain (N1IC), the activated form of the Notch1 receptor, can modulate downstream target genes via C promoter-binding factor 1–dependent and -independent pathways. To further dissect the Notch1 signaling pathway, we screened the N1IC-associated proteins using a yeast two-hybrid system and identified nuclear βII-tubulin as a candidate for the N1IC-associated proteins. It was suggested that the presence of βII-tubulin in nuclei might be correlated with the cancerous state of cells. However, the function of βII-tubulin locating in the nucleus still is unknown. Herein, we show that the complex of α- and βII-tubulin is associated with N1IC in cancer cells by a coimmunoprecipitation analysis. The ankyrin domain of the Notch1 receptor alone was sufficient to associate with βII-tubulin. Furthermore, α- and βII-tubulin were localized in the nucleus and formed a complex with N1IC. Treatment with Taxol increased the amounts of nuclear α- and βII-tubulin in K562 and HeLa cells and promoted the C promoter-binding factor 1–dependent transactivation activity of N1IC. We also show that nuclear βII-tubulin was bound on the C promoter-binding factor 1 response elements via the association with N1IC. These results suggest that nuclear βII-tubulin can modulate Notch signaling through interaction with N1IC in cancer cells.

A proteomic analysis of secreted proteins from xylan-induced Bacillus sp. strain K-1.

The expression level of extracellular proteins in an alkaliphilic bacterium, Bacillus sp. strain K‐1, grown in a xylan‐containing medium, is significantly increased when compared with that grown in the nonxylan culture medium. A proteomic approach has been efficiently applied to separate and characterize these differentially expressed secretory proteins. Eight prominent protein spots were identified and subjected to N‐terminal amino acid sequencing. The results show that three spots share considerable similarity with the xylanolytic enzymes and that two spots share considerable similarity with the GltC regulatory protein and 3‐dehydroquinate dehydratase, respectively. In addition, the three other proteins show little similarity with the known proteins in the database. In conclusion, our results demonstrate that the proteomic approach is a highly efficient method to rapidly study the differential expression of the secreted proteins by Bacillus sp. strain K‐1 grown under xylan‐induced condition.

Microwave-assisted Heterogeneous Benzil–Benzilic Acid Rearrangement

A new procedure for carrying out the benzil–benzilic acid rearrangement in the solid state has been developed which provides a new route to synthesize the pharmacologically interesting anticonvulsant dilantin.