OmpC and OmpF are required for growth under hyperosmotic stress above pH 8 in Escherichia coli

AIMS: To investigate the requirement of outer membrane porins for osmotic adaptation at alkaline pH in Escherichia coli. METHODS AND RESULTS: Escherichia coli mutants deficient in ompC, ompF and both genes were constructed and the growth of these mutants was observed at alkaline pH. The growth rate of the mutant deficient in both ompC and ompF was slower than that of the wild type and mutants deficient in one of these genes under hyperosmotic stress at pHs above 8.0. The decreased rate was recovered when a cloned ompC was introduced to the mutant, but the growth recovery with a cloned ompF was partial. Such growth diminution was not observed at pHs below 8.0. CONCLUSION: OmpC and OmpF were shown to participate in hyperosmotic adaptation at alkaline pH in E. coli. SIGNIFICANCE AND IMPACT OF THE STUDY: This study is the first report to demonstrate that OmpC and OmpF are required for hyperosmotic adaptation at pHs above 8.0, but not below 8.0.     

Adenoviral-mediated transfer of human wild-type p53, GM-CSF and B7-1 genes results in growth suppression and autologous anti-tumor cytotoxicity of multiple myeloma cells in vitro

Multiple myeloma (MM) remains incurable despite the use of high-dose chemotherapy and stem cell transplantation. However, immunotherapy is expected to offer long-term disease control, or even possibly a cure. We have previously demonstrated the suppressive effect of a recombinant adenovirus carrying human wild-type p53, granulocyte–macrophage colony-stimulating factor, and B7-1 genes (Ad-p53/GM-CSF/B7-1) on the growth of laryngeal cancer cells. In the present study, we evaluated the effects of an Ad-p53/GM-CSF/B7-1-modified myeloma cell vaccine strategy aimed to induce apoptosis and to augment the immunogenicity of MM cells. Both MM cell lines and purified primary myeloma cells were infected with Ad-p53/GM-CSF/B7-1. High expression levels of these three genes were confirmed separately by Western blot, enzyme-linked immunosorbent assay (ELISA), and flow cytometry. When wild-type p53, GM-CSF and B7-1 genes were introduced, the growth of MM cells was inhibited via enhanced apoptosis and the immunogenicity of tumor cells was augmented. The combinatorial effect of these three genes on inducing cytotoxic T lymphocytes (CTLs) was more evident than that of p53 individually or any combinations of two (p53 plus GM-CSF or p53 plus B7-1). Furthermore, significant proliferation of autologous peripheral blood lymphocytes (PBLs) and specific cytotoxicity against autologous primary MM cells were induced in vitro. These results suggest that myeloma cell vaccination co-transferred with p53, GM-CSF and B7-1 genes may be a promising immunotherapeutic approach against MM.     

Mutation of a family 8 glycosyltransferase gene alters cell wall carbohydrate composition and causes a humidity-sensitive semi-sterile dwarf phenotype in Arabidopsis

Incompatible plant-pathogen interactions result in the rapid cell death response known as hypersensitive response (HR) and activation of host defense related genes. To understand the cellular mechanism controlling defense response better, a novel pathogenesis-related (PR) gene and putative cell wall protein gene, CaTin2, was isolated through differential screening of a hot pepper cDNA library and characterized. CaTin2 gene was locally and systemically induced in hot pepper plants upon TMV-P₀ inoculation which induces HR. However, CaTin2 gene wasn't regulated by bacterial HR-specific signal pathway. The full-length cDNA for CaTin2, which is 864 nucleotides long, contained the open reading frame of 200 amino acids including cell wall targeting sequences of 26 amino acids. CaTin2 gene has no sequence similarity with other cell wall protein genes except the signal sequence and exists as only one copy in hot pepper genome. CaTin2 gene contains repeated helix-turn-helix motif consisting of 39 amino acids. CaTin2 mRNA accumulation was induced in response to various treatments such as ethylene, SA, MeJA, ABA, methyl viologen, NaCl and wounding at early time points. Subcelluar localization of CaTin2 was confirmed in the cell wall in hot pepper leaves by making CaTin2::smGFP fusion protein. The transgenic plants overexpressing CaTin2 cDNA were resistant to TMV and CMV inoculation. From these results, CaTin2 gene may encode a virus-related new cell wall protein member.     

Molecular basis of the pharmacological difference between rat and human bombesin receptor subtype-3 (BRS-3)

We cloned the gene and cDNA for rat bombesin receptor subtype-3 (BRS-3) and characterized its mRNA expression pattern and pharmacological properties. Despite the high degree of sequence similarity (80% identical), rat and human BRS-3 differ markedly in their pharmacological properties. Although the natural ligand for BRS-3 is still unknown, a synthetic peptide, dY-Q-W-A-V-(beta-A)-H-F-Nle-amide (dY-bombesin), activates human BRS-3 with an EC(50) of 1.2 nM. In contrast, dY-bombesin had a very poor potency for rat BRS-3 (EC(50) = 2 microM). To understand the molecular basis of this pharmacological difference, we constructed chimeric receptors in which individual extracellular loops of rat BRS-3 were replaced with the corresponding human sequences. Switching the N-terminal region or the second extracellular loop did not significantly change receptor properties. However, switching the third extracellular loop (E3) in the rat BRS-3 resulted in a chimeric receptor (RB3-E3) that behaved almost identically to human BRS-3. RB3-E3 bound dY-bombesin with high affinity (K(i) = 1.2 +/- 0.7 nM), and was activated by dY-bombesin with high potency (EC(50) = 1.8 +/- 0.5 nM). Within the E3 loop, mutation of Y(298)E(299)S(300) to S(298)Q(299)T(300) (RB3-SQT) or of D(306)V(307)P(308) to A(306)M(307)H(308) (RB3-AMH) only partially mimicked the effect of switching the entire E3 loop, and mutation of A(302)E(303) to V(302)D(303) or of V(310)V(311) to I(310)F(311) had little effect on the dY-bombesin potency. These results indicate that the sequence variation in the E3 loop is responsible for the species difference between rat and human BRS-3, and multiple residues in the E3 loop are involved in interactions with the agonist dY-bombesin.     

DNA sequences and expression in Streptomyces lividans of an exoglucanase gene and an endoglucanase gene from Thermomonospora fusca.

Two genes encoding cellulases E1 and E4 from Thermomonospora fusca have been cloned in Escherichia coli, and their DNA sequences have been determined. Both genes were introduced into Streptomyces lividans, and the enzymes were purified from the culture supernatants of transformants. E1 and E4 were expressed 18- and 4-fold higher, respectively, in S. lividans than in E. coli. Thin-layer chromatography of digestion products showed that E1 digests cellotriose, cellotetraose, and cellopentaose to cellobiose and a trace of glucose. E4 is poor at degrading cellotriose and cleaves cellopentaose to cellotetraose and glucose or cellotriose and cellobiose. It readily cleaves cellotetraose to cellobiose. E1 shows 59% identity to Cellulomonas fumi CenC in a 689-amino-acid overlap, and E4 shows 80% identity to the N terminus of C. fimi CenB in a 441-amino-acid overlap; all of these proteins are members of cellulase family E. Alignment of the amino acid sequences of Clostridium thermocellum celD, E1, E4, and four other members of family E demonstrates a clear relationship between their catalytic domains, although there is as little as 25% identity between some of them. Residues in celD that have been identified by site-directed mutagenesis and chemical modification to be important for catalytic activity are conserved in all seven proteins. The catalytic domains of E1 and E4 are not similar to those of T. fusca E2 or E5, but all four enzymes share similar cellulose-binding domains and have the same 14-bp inverted repeat upstream of their initiation codons. This sequence has been identified previously as the binding site for a protein that regulates induction.     

Many parallel losses of infA from chloroplast DNA during angiosperm evolution with multiple independent transfers to the nucleus

We used DNA sequencing and gel blot surveys to assess the integrity of the chloroplast gene infA, which codes for translation initiation factor 1, in >300 diverse angiosperms. Whereas most angiosperms appear to contain an intact chloroplast infA gene, the gene has repeatedly become defunct in approximately 24 separate lineages of angiosperms, including almost all rosid species. In four species in which chloroplast infA is defunct, transferred and expressed copies of the gene were found in the nucleus, complete with putative chloroplast transit peptide sequences. The transit peptide sequences of the nuclear infA genes from soybean and Arabidopsis were shown to be functional by their ability to target green fluorescent protein to chloroplasts in vivo. Phylogenetic analysis of infA sequences and assessment of transit peptide homology indicate that the four nuclear infA genes are probably derived from four independent gene transfers from chloroplast to nuclear DNA during angiosperm evolution. Considering this and the many separate losses of infA from chloroplast DNA, the gene has probably been transferred many more times, making infA by far the most mobile chloroplast gene known in plants.     

A sensitive multiplex assay for piRNA expression

PIWI-interacting RNAs (piRNAs) are a new class of small RNAs specifically expressed in male germ cells. It is known to bind to PIWI class of Argonaute proteins, Mili and Miwi. To help to decipher the mechanism of piRNA function, here, we report a real time PCR-based multiplex assay for piRNA expression. Firstly, we showed that the assay specifically detects piRNA expression in adult testis, consistent with the Northern blot result. The method we developed can simultaneously detect at least eight piRNAs using only 10 pg total RNA, which is equivalent to the RNA present in a single cell. This is five to six order magnitude more sensitive than corresponding Northern blot assays. Finally we used this assay to analyze eight piRNAs expression in mouse primordial germ cells (PGCs) in genital ridges from E12.5, at the time when piRNA-binding protein Mili starts to be detected in PGCs. This multiplex piRNA assay can be further expanded to assay a few hundred of piRNAs simultaneously from as little as total RNA from a single cell. This approach will help to understand the mechanism and function of piRNAs during germ cell development.