A comparison was made of bacteriophage MS2 RNA translation in infected Escherichia coli cells and in a defined cell-free system. A number of temperature-sensitive mutants were used as hosts for viral RNA translation at permissive and restrictive temperatures. The amount of viral coat protein synthesis was determined after gel electrophoresis of proteins from the cell lysates. These results were compared to those obtained with cell-free translation assays conducted with ribosomes isolated from the same mutants. Compared with control cells, a reduced activity in vivo and in vitro was found for each mutant examined at elevated temperatures. A good correlation between the two types of translational assays was observed. These findings are discussed in terms of the translational defects known to be a characteristic of some of these mutant strains.

Indiana University-Purdue University Indianapolis (IUPUI) / Lyme disease is a multi-system inflammatory disorder that is currently the fastest growing arthropod-borne disease in the United States. The Lyme disease pathogen, Borrelia burgdorferi, exists within an enzootic cycle consisting of Ixodes tick vectors and a variety of vertebrate hosts. Borrelia lies within a distinct clade of microorganisms known as spirochetes which exhibit a unique spiral morphology. The underlying genetic mechanisms controlling for borrelial morphologies are still being discovered. One flagellar protein, FlaB, has been indicated to affect both spiral shape and motility of the organisms and significantly impacts the organism’s ability to establish infection. Due to the potential connection between morphological characteristics and pathogenesis, we sought to screen and identify morphological mutants in an attempt to identify genes associated with morphological phenotypes of Borrelia burgdorferi. Among Borrelia’s unique features is the presence of abundant lipoproteins making up its cellular membrane as opposed to the typical lipopolysaccharides. These proteins confer a wide variety of functions to the microorganism, among which include the abilities to circulate between widely differing hosts and to establish infection. Two important outer surface proteins, OspC and OspA, are found to be inversely expressed throughout the borrelial life cycle. OspC, in particular, becomes highly expressed during tick-feeding and transmission to the mammalian host. It has been found to be essential for establishment of infection. A global regulatory pathway has been shown to control for OspC, however there are missing links in this pathway between the external stimuli (such as temperature, pH, and cell density) and the regulatory pathway. We have performed a screening process to identify OspC expression mutants in order to identify novel genes associated with this pathway.

In effort to understand and isolate genes that are associated with protein secretion, the Lin-Cereghino laboratory at University of the Pacific created mutant strains of Pichia pastoris using the restriction enzyme mediated integration method. The mutants exhibited an unusual ability to supersecrete beta-galactosidase, due to the effects of a randomly disrupted gene by pREMI-Z. To learn more about the novel effects of the gene disruption, nine beta-galactosidase supersecreters ( bgs ) have been characterized for their phenotypes such as growth rate, cell wall integrity, and ability to produce and secrete various types of recombinant proteins. The mutants showed various population doubling times, which ranged from 1.7 to 2.4 hours. Generally, the mutants with severely diminished growth rates had much lower secretion of the reporter proteins. The mutants also showed different levels of cell wall (osmotic) defect, indicated by moderate to severe leakage of alkaline phosphatase from the vacuole. It was revealed that the cell wall defect was not necessarily associated with increased protein secretion, which suggests that the cell wall may not be a limiting barrier for the secretion of most reporter proteins. The result of the reporter study suggests that the secretion phenotypes of bgs mutants were protein specific and likely to be dependent upon the structure of the secreted protein rather than the size.

京都大学 / 0048 / 新制・論文博士 / 博士(農学) / 乙第12878号 / 論農博第2805号 / 新制||農||1028(附属図書館) / 学位論文||H26||N4877(農学部図書室) / 31596 / (主査)教授 保川 清, 教授 安達 修二, 教授 伏木 亨 / 学位規則第4条第2項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第21253号 / 医博第4371号 / 新制||医||1029(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 横出 正之, 教授 浅野 雅秀, 教授 松本 智裕 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

The overall architecture and cell types are highly conserved from mammals to teleost fish. The rapid transparent ex utero development in zebrafish allows direct access and precise visualization of all the major events in cerebellar development. The superficial position of the cerebellar primoridum and cerebellum further facilitates in vivo imaging of cerebellar structures and developmental events at cell resolution. Furthermore, zebrafish model have a comprehensive genetic toolbox that allow forward and reverse genetic approaches to study and manipulate gene function. Consequently, zebrafish is emerging as an excellent vertebrate model for studies of molecular, cellular and physiological mechanisms involved in cerebellar development and function at gene, cell and circuit level.

Legumes are unique plants because they form special structures “nodules”, via symbiotic relationships with rhizobial bacteria present in the soil. Once rhizobia mature inside nodules, they fix atmospheric nitrogen providing a source of bioavailable nitrogen to the plant. To discover novel genetic components involved in the legume-rhizobia symbiosis by using forward genetic screening, we have isolated Medicago truncatula Tnt1 insertion mutants in the R108 ecotype, which are defective in nodule development and symbiotic nitrogen fixation in response to Sinorhizobium meliloti. Out of three mutants NF11044, NF11217 and NF8324, one of the mutants showed brown nodules and Fix- phenotype that is defective in symbiotic nitrogen fixation. The other two mutants showed white nodules and Fix- phenotype, also indicator of defects in symbiotic nitrogen fixation. To identify the underlying mutation causing the phenotype, we have developed molecular genetic markers by obtaining genomic sequences flanking the Tnt1 insertions by TAIL-PCR and Illumina sequencing. To carry out co-segregation analysis, back-crossed BC1F2 segregating populations were obtained. These are being phenotyped, genotyped and analyzed for co-segregation of the phenotype with the Tnt1 genetic markers. Back-crossing also has the effect of reducing the Tnt1 insertions, which are not linked to the nodulation defective phenotypes. Out of the three mutants, NF8324 harbors exactly the same insertion as in the rsd-1 Tnt1 mutant NF11265. The defect in NF11217 is caused by a Tnt1 insertion in the previously described PLC gene; the site of this insertion is close to that found in a different mutant, NF0217. For mutant NF11044, we developed linkage markers that place the defective locus on chromosome 7. To further characterize co-segregation in NF11044, a mapping population has been created by crossing the mutant with other ecotypes: A17 and A20. We tested mutants and wild type plants with linkage marker A20 X NF11044 BC1F2 that segregates 3:1(wild type: mutant). The recombination frequency ratio is similar as compared to back-crosses to ecotype R108. However, we did not observe mutant phenotypes in the A17 X NF11044 BC1F2 population. Future identification of the defective gene and functional characterization of it once it is identified will be carried out to better understand the mechanism of nodule organogenesis and symbiotic nitrogen fixation.

No description available.

<p>Regulators of G protein signaling (RGS) proteins are key negative regulators of Gα signaling, a branch of G-protein-coupled receptor (GPCR)-mediated signal transduction. Approximately 35% of drugs approved by the Food and Drug Administration (FDA) target GPCRs, so it is not surprising that the discovery of RGS proteins has triggered an interest in them as new drug targets. Even though many studies have been shown the involvement of RGS proteins in cancers, there is still a knowledge gap in understanding function and regulation of RGS proteins in these diseases. Consequently, in this thesis, I explored roles of two RGS proteins that have been implicated in cancers.</p> <p>RGS2 is proposed to act as a tumor suppressor in many different cancers, such as breast cancer, bladder, and ovarian cancer. Here, we investigated if RGS2 also plays a tumor suppressor role in UM, whose growth is driven by overactivated Gαq/11 signaling. We found that increased expression levels of RGS2 inhibit cell growth of UM 92.1 and Mel-202 cells. Mechanistically, this cell growth inhibition is dependent on the association between RGS2 and Gαq, but independent of its canonical GTPase-accelerating protein (GAP) activity. Furthermore, RGS2 inhibited the Mitogen-activated protein kinases (MAPK) signaling, downstream of Gαq, while leaving Yes-associated protein 1/Transcriptional coactivator with PDZ-binding motif (YAP/TAZ) activation unaffected. These data indicate a tumor suppressor role for RGS2 in UM and proposes RGS2 stabilization as a potential therapeutic targeting strategy. </p> <p>In contrast to RGS2, RGS20 contributes to cancer progression, particularly in breast cancer. However, how RGS20 is regulated is understudied. Palmitoylation, a reversible post-translational modification, regulates functions of other RGS proteins, and RGS20 is predicted to be palmitoylated. We provided direct evidence of RGS20 palmitoylation in cells and validated the palmitoylation site as the conserved cysteine (Cys148) in the RGS domain. Our results showed that palmitoylation on this site does not affect its GAP activity and subcellular localization, but it affects the association between RGS20 and active Gαo, and inhibition of Gαo-mediated signaling. This study serves as a foundation for future studies in furthering understating the role of palmitoylation in RGS20 function and its possible implications in cancer biology. </p>

No description available.