Aging and disease processes may be due to deleterious and irreversible changes produced by free radical reactions. The enzyme copper-zinc superoxide dismutase (CuZn SOD; superoxide: superoxide oxidoreductase, EC 1.15.1.1) performs a protective function by scavenging superoxide radicals. In order to determine whether additional SOD activity affects longevity and oxygen metabolism in Drosophila, our approach was to clone the Sod gene and introduce additional copies of the gene back into the genome via P element mediated transformation. The effects of increased SOD activity on Drosophila life span and oxygen free radical metabolism were investigated. The CuZn SOD cDNA and gene were cloned from Drosophila melanogaster. The sequence of the Sod cDNA and gene revealed an additional C-terminal triplet coding for valine not found in the mature SOD protein. The nucleotide sequence of the coding region has 56% and 57% identity when compared to the corresponding human and rat Sod genes, respectively. A probe of the cloned gene hybridizes to position 68A4-9 on Drosophila polytene chromosomes. In wild-type Drosophila the Sod cDNA hybridizes to a 0.7-0.8 kb transcript which is greatly diminished in a SOD 'null' mutant that produces only 3.5% of the SOD protein. A 1.8 kb EcoRI gene fragment containing the Sod gene was cloned into the P vector pUChsneo and microinjected into Drosophila embryos. Five transformed lines, each of which contain an additional copy of the Sod gene at different chromosomal sites were constructed. The chromosomal positions of the transposed Sod sequence were determined by in situ hybridization of the Sod gene to salivary gland polytene chromosomes. Analysis of RNA from the transformed flies revealed that the transposed Sod gene was expressed. The range of SOD activity for the five transformed lines was 131% to 170% of the value of wild-type. There was good correlation between the amount of Sod mRNA and the level of SOD activity in the transformed lines. Increased SOD levels in the transformed lines did not confer greater resistance to paraquat-generated superoxide radicals, nor increase their lifespan. The SOD 'null' mutant with 3.5% of the wild-type SOD activity was hypersensitive to paraquat when compared to wild-type, whereas the heterozygous SOD deficiency Df(3L)1xd⁹/TM3SbSer with 50% of the wild-type SOD activity was not. Mutants lacking SOD are dramatically impaired in oxygen metabolism and a few percent of wild-type activity appears to provide significant protection against superoxide, while 50% of the wild-type levels confers essentially the same resistance as wild-type. Despite the observation that the SOD activities found in a wide range of animals correlates directly with their longevity, Drosophila melanogaster appears to be well protected against the toxic effects of oxygen by its native levels of SOD. / Arts, Faculty of / Philosophy, Department of / Graduate

Carbonic anhydrase is a ubiquitous zinc-metalloenzyme that catalyzes the interconversion of carbon dioxide and carbonate and has been found to play a wide range of roles in animals, plants and bacteria. Cotton genomic and cDNA libraries were screened for the plastidial isoform of carbonic anhydrase. The nucleotide sequences of two 1.2 Kb partial cDNA clones were determined. These clones exhibit high homology to carbonic anhydrases from other dicot plants and possess all the expected peptide motifs. For example, serine and threonine rich chloroplastic targeting peptide and conserved zinc binding residues are both present. These clones were utilized to isolate two carbonic anhydrase genes that were shown to encode different isoforms by PCR and RFLP analysis.

Pichia pastoris, a popular protein expression system, is limited in its ability to secrete heterologous proteins. The PMR1 gene, the disruption of which is known to improve the secretion of prochymosin, human prourokinase, and human tissue plasminogen activator in Saccharomyces cerevisiae, was cloned from P. pastoris. The pmr 1 mutant in S. cerevisiae also displayed a slow growth phenotype when grown on low Ca2+ medium. The putative P. pastoris PMR1 gene, encoding for a 924 amino acid P-type Ca2+ ATPase, was disrupted in P. pastoris and the secretion of horseradish peroxidase (HRP) and β-galactosidase (β-gal) analyzed. Secreted HRP activity was determined using 3,3',5,5' tetramethylbenzidine (TMB) colorimetric assay and western analysis. β-gal expression and secretion was determined by western analysis. Secretion in P. pastorius Δpmr1 for both heterologous proteins showed no appreciable difference compared to wild type, nor did P. pastoris Δpmr1 display the slow growth phenotype seen in S. cerevisiae Δpmr1 (Rudolph H. et al., 1989).

Methodology was developed which allowed the rapid and routine quantitation of subpicomole quantities of diadenosine-5ʹ,5ʹʹʹ-P¹,P⁴-tetraphosphate (Ap₄A) in cultured mammalian cells. This methodology includes the rapid extraction of cellular nucleotides in cold alkali, resolution of Ap₄A from the bulk of cellular materials on a highly specific boronate affinity resin, and quantitation of the dinucleotide in a coupled bioluminescence assay utilizing venom phosphodiesterase and firefly luciferase. The sensitivity and selectivity of this assay is demonstrated and contrasted with previously developed techniques. This assay was used to examine the role of Ap₄A in DNA replication and the cellular stress response.

Myelodysplastic syndromes (MDS) encompass a heterogeneous group of age-related hematopoietic disorders characterized by ineffective and incomplete hematopoiesis leading to an increased risk of acute myeloid leukemia (AML). The development of accurate and easily used in vitro models is crucial for understanding the pathogenesis of MDS and identifying potential therapeutic targets. Induced pluripotent stem cells (iPSCs) can be used to study MDS due to their ability to differentiate into any cell type depending on the environment. The main limitation is that the blood progenitors produced by iPSCs are of a fetal state, which hinders modeling of MDS, a disease of older adulthood. This study aimed to optimize the maturation state of blood progenitors derived from iPSCs by induction of the micro-RNA let-7, which, we hypothesize will increase the maturation and adult phenotypic state of hematopoietic progenitors. iPSC lines were generated from healthy controls and samples containing the SRSF2 mutation, a common mutation in MDS, containing a doxycycline-inducible, stabilized let-7 transgene. A stepwise differentiation efficiently drove the iPSCs toward hematopoietic progenitors and, subsequently, other mature lineages. The hematopoietic progenitors were characterized by assessing the expression of specific cell surface markers and functional properties using flow cytometry, colony-forming assays, and multi-lineage differentiation abilities. These findings demonstrate the potential of using iPSC engineering to create a novel model for MDS and other age-biased disorders by inducing let-7 expression in iPSCs and, when differentiating them, exposing them to doxycycline to promote an adult cell phenotype. This approach offers a valuable potential tool for elucidating the molecular mechanisms underlying these disorders and exploring potential therapeutic interventions. / 2026-03-13T00:00:00Z

No description available.

Thesis (MSc (Biochemistry))--University of Stellenbosch, 2005. / This study describes: 1. The cloning of baboon cytochrome P450 side-chain cleavage (CYP11A1) cDNA by in vitro site-directed mutagenesis. 2. The identification and sequencing of three baboon CYP11A1 mutants: CYP11A1a, CYP11A1b and CYP11A1c. 3. The expression and characterisation of baboon and human CYP11A1 cDNA, CYP11A1a, CYP11A1b and CYP11A1c in nonsteroidogenic COS-1 cells. The Km and V-values for the metabolism of 25-hydroxycholesterol were determined. 4. The construction of the first homology model of CYP11A1, using both mammalian (CYP2C5) and bacterial (CYP102) cytochromes P450 crystal structures as templates. 5. A structure/function study into the role of the amino acid residues Ile98, Lys103 and Thr291 in substrate binding and enzymatic activity. 6. The proposal of a topological model of the CYP11A1 active pocket as determined by substrate docking studies.

Para a obtenção da seqüência completa do cDNA da α-amilase foi realizada a varredura de uma biblioteca de cDNA, utilizando-se iniciadores planejados a partir do consenso entre seqüências de DNA ou aminoácidos disponíveis em bancos de dados. Após a excisão do vetor pBK-CMV carregando o inserto, foram obtidos subclones e todos foram seqüênciados. Foi obtida uma seqüência clonada de 1971pb, contendo uma ORF de 1251pb, codificando uma proteina de 416 aminoácidos (aa). Esta proteína apresentou urn provável peptídeo sinal de 15 aa, peso molecular calculado de 45.080 Da e pI 5,84. A seqüência de bases obtida mostrou similaridade de 75% quando comparada corn genes de outras monocotiledôneas como arroz, milho, cevada e trigo. Para a seqüência de aminoácidos, deduzida a partir região codificadora, esta semelhança foi de ate 80%, mostrando-se altamente conservada. Os modelos das estruturas primária, secundária e terciária para a α-amilase de banana coincidem em diversos pontos com estruturas determinadas por cristalografia de raios X para α-amilases de outras espécies, incluindo a disposição espacial de resíduos catalíticos e de ligação de substrato e íons cálcio. Análises por northern e Southern blot sugerem que apesar da existência de uma família de genes corn múltiplas cópias, a expressão destes nas frutas não alcança níveis detectáveis por northern blot. / Abstract not available.

Chan Ka Ping Sophie. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 140-144). / Abstracts in English and Chinese. / Thesis/Assessment Committee --- p.i / Acknowledgements --- p.ii / Abstract --- p.viii / 摘要 --- p.x / Abbreviations --- p.xi / List of Figures --- p.xii / List of Tables --- p.xiv / Chapter 1 --- Introduction / Chapter 1.1 --- Pathogenesis of HBV Infection --- p.1 / Chapter 1.2 --- Classification and Structure --- p.2 / Chapter 1.3 --- HBV Genome --- p.4 / Chapter 1.4 --- Replication Cycle --- p.7 / Chapter 1.5 --- HBV Genotypes and Nomenclature --- p.9 / Chapter 1.5.1 --- Asian prevalent genotypes --- p.9 / Chapter 1.5.2 --- Numbering system --- p.9 / Chapter 1.6 --- Identification of Markers in HBV Genome for HCC Development --- p.11 / Chapter 1.7 --- Project Objective --- p.13 / Chapter 1.8 --- Promoters of HBV --- p.14 / Chapter 1.8.1 --- Pre-S1 promoter --- p.14 / Chapter 1.8.2 --- X promoter and enhancer I --- p.14 / Chapter 1.8.3 --- Core promoter and enhancer II --- p.15 / Chapter 1.8.4 --- Pair of mutations at BCP --- p.17 / Chapter 2 --- Materials and Methods / Chapter 2.1 --- Construction of pGL3-promoter Plasmids --- p.18 / Chapter 2.1.1 --- Templates selection --- p.18 / Chapter 2.1.2 --- Amplification of promoters --- p.19 / Chapter 2.1.3 --- Cloning into pGL3-basic vector --- p.21 / Chapter 2.1.4 --- Screening and plasmid preparation --- p.21 / Chapter 2.2 --- Construction of Mutant Promoter Clones --- p.23 / Chapter 2.2.1 --- Site-directed mutagenesis --- p.23 / Chapter 2.2.2 --- pPreS 1 /2712C mutant clone --- p.24 / Chapter 2.3 --- Cloning of Full-length HBV Genomes --- p.26 / Chapter 2.3.1 --- Replication-competent HBV clone --- p.26 / Chapter 2.3.2 --- Amplification of full-length HBV genome --- p.28 / Chapter 2.3.3 --- Cloning into pUC19 vector --- p.28 / Chapter 2.3.4 --- Screening for insert and sequence confirmation --- p.29 / Chapter 2.3.5 --- Excision of full-length HBV from plasmid --- p.29 / Chapter 2.4 --- Re-construction into a 1.3-fold HBV Clone --- p.32 / Chapter 2.4.1 --- Cloning of HBV fragment nucleotide 979-2617 (nt 979-2617) --- p.32 / Chapter 2.4.2 --- Screening for insert and sequence confirmation --- p.33 / Chapter 2.4.3 --- Cloning of HBV fragment (nt 905-2000) --- p.33 / Chapter 2.4.4 --- Construction of a 1.3-fold HBV genotype Cs clone --- p.34 / Chapter 2.5 --- Cell Culture --- p.37 / Chapter 2.5.1 --- Cell culture maintenance --- p.37 / Chapter 2.5.2 --- Transient transfection of promoter clones --- p.37 / Chapter 2.5.3 --- Transient transfection of HBV genomes --- p.38 / Chapter 2.6 --- Dual-Luciferase® Reporter Assay System --- p.40 / Chapter 2.6.1 --- Principle of the assay --- p.40 / Chapter 2.6.2 --- Cell harvest --- p.43 / Chapter 2.6.3 --- Luciferase assay --- p.43 / Chapter 2.7 --- Data Analysis --- p.44 / Chapter 2.8 --- Extraction of HBV DNA from Intracellular Cores --- p.45 / Chapter 2.8.1 --- Harvest of intracellular cores --- p.45 / Chapter 2.8.2 --- Phenol/chloroform extraction --- p.45 / Chapter 2.9 --- Southern Blotting --- p.47 / Chapter 2.9.1 --- Transfer of DNA to membrane --- p.47 / Chapter 2.9.2 --- Preparation of probes --- p.47 / Chapter 2.9.3 --- Hybridization with radiolabeled probes --- p.48 / Chapter 2.10 --- Detection of HBeAg and HBsAg --- p.50 / Chapter 2.10.1 --- HBsAg assays --- p.50 / Chapter 2.10.2 --- HBeAg assays --- p.51 / Chapter 2.11 --- SEAP Reporter Gene Assay --- p.52 / Chapter 3 --- Results / Chapter 3.1 --- Templates Selected --- p.53 / Chapter 3.2 --- Results of Luciferase Assays --- p.58 / Chapter 3.2.1. --- BCP mutation of genotype A as control --- p.58 / Chapter 3.2.2. --- Effect of C1165T mutation on Xpro/enhI activity of HBV genotype B --- p.60 / Chapter 3.2.3. --- Effect ofT2712C mutation on pre-S1 promoter activity of HBV Genotype B --- p.60 / Chapter 3.2.4. --- Effect of G1613A mutation on core pro/enhII activity of HBV Genotype Cs --- p.64 / Chapter 3.2.5. --- G1613A and BCP mutation --- p.67 / Chapter 3.3 --- Full-length HBV Genome Clones --- p.70 / Chapter 3.3.1. --- Construction of replication-competent full-length HBV genome clones --- p.70 / Chapter 3.3.2. --- Drawbacks of the system --- p.78 / Chapter 3.4 --- Construction of a Replication-competent 1.3-fold HBV Clone --- p.82 / Chapter 3.4.1. --- Construction of the HBV (nt 979-2617) clone --- p.82 / Chapter 3.4.2. --- Construction of the HBV (nt 905-2000) clone --- p.86 / Chapter 3.4.3. --- Construction of 1.3-fold genotype Cs HB V clone --- p.89 / Chapter 3.4.4. --- Test for replication competency --- p.92 / Chapter 4 --- Discussion / Chapter 4.1 --- BCP Mutation as Control of the Luciferase Assay --- p.94 / Chapter 4.2 --- Promoter Activities Not Altered by T2712C and C1165T --- p.96 / Chapter 4.3 --- Mutation G1613A of Core pro/enhll --- p.98 / Chapter 4.3.1 --- Mutation resides in negative regulatory element of core promoter --- p.98 / Chapter 4.3.2 --- NRE and NRE-binding protein --- p.98 / Chapter 4.3.3 --- Relationship with BCP mutation --- p.101 / Chapter 4.4 --- HBV Constructs --- p.103 / Chapter 4.4.1 --- Rationale in re-construction of 1.3-fold HB V clone --- p.103 / Chapter 4.4.2 --- Replication competency --- p.104 / Chapter 4.5 --- Conclusion --- p.106 / Chapter 4.6 --- Future Work --- p.107 / Appendix --- p.108 / References --- p.140

by Peter, Wei Gong Chang. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (leaves 103-124). / ACKNOWLEDGEMENTS --- p.i / ABSTRACT --- p.ii / TABLE OF CONTENTS --- p.iv / ABBREVIATIONS --- p.viii / Chapter CHAPTER 1 --- INTRODUCTION / Chapter 1.1 --- General introduction --- p.1 / Chapter 1.2 --- Human genome project --- p.5 / Chapter 1.3 --- Human adult heart cDNA library --- p.7 / Chapter 1.4 --- Human fetal heart cDNA library --- p.8 / Chapter 1.5 --- Sequencing of a human heart cDNA clone --- p.9 / Chapter 1.6 --- Knowledge of the role of selenium --- p.13 / Chapter 1.7 --- Mouse 56kDa selenium binding protein and acetaminophen-binding protein --- p.16 / Chapter CHAPTER 2 --- MATERIALS AND METHODS / Chapter 2.1 --- Plating out the cDNA library --- p.20 / Chapter 2.1.1 --- "Mediums, buffers and solutions" --- p.20 / Chapter 2.1.2 --- Bacteriophage clones preparation --- p.21 / Chapter 2.2 --- cDNA clone amplification by PCR --- p.23 / Chapter 2.3 --- Cycle sequencing of PCR products --- p.25 / Chapter 2.3.1 --- "Media, buffers and solutions" --- p.25 / Chapter 2.3.2 --- Preparation of sequencing reaction --- p.25 / Chapter 2.4 --- Gel electrophoresis using an automated A.L.F sequencer --- p.27 / Chapter 2.5 --- DNA sequence analysis --- p.29 / Chapter 2.6 --- Preparation of competent E. coli for transformation --- p.30 / Chapter 2.7 --- Transformation of plasmid into competent E. coll --- p.31 / Chapter 2.8 --- Mini-preparation of plasmid DNA --- p.32 / Chapter 2.9 --- Large scale plasmid DNA preparation by QIAGEN --- p.34 / Chapter 2.10 --- Cloning the human 56 kDa selenium binding protein (hSP56) into the pAED4 vector --- p.36 / Chapter 2.10.1 --- Bacterial strains and vector --- p.36 / Chapter 2.10.2 --- "Media, buffers and solutions" --- p.38 / Chapter 2.10.3 --- Primers design and PCR --- p.42 / Chapter 2.10.4 --- Purification of PCR products by Geneclean --- p.43 / Chapter 2.10.5 --- Restriction digestion of purified PCR product and pAED4 --- p.44 / Chapter 2.10.6 --- Ligation and transformation of hSP56 --- p.45 / Chapter 2.10.7 --- Screening and purification ofpAED4hSP56. --- p.47 / Chapter 2.11 --- Expression of hsp56 --- p.50 / Chapter 2.11.1 --- Induction of hSP56 expression --- p.50 / Chapter 2.11.2 --- SDS-PAGE and protein detection --- p.51 / Chapter 2.12 --- Northern hybriddization of hSP56 --- p.53 / Chapter 2.12.1 --- Animals & human tissue --- p.53 / Chapter 2.12.2 --- "Mediums, buffers and solutions" --- p.53 / Chapter 2.12.3 --- Preparation of total RNA --- p.56 / Chapter 2.12.4 --- Formaldehyde agarose gel electrophoresis --- p.57 / Chapter 2.12.5 --- Preparation of radioactive probe --- p.58 / Chapter 2.12.6 --- RNA transfer and Northern hybridization --- p.59 / Chapter 2.13 --- Chromosomal mapping of the hSP56 gene --- p.62 / Chapter CHAPTER 3 --- RESULTS / Chapter 3.1 --- The sequencing results of 553 cDNA clones --- p.63 / Chapter 3.2 --- Catalogues of genes expressed --- p.65 / Chapter 3.3 --- Sequence analysis of hSP56 --- p.71 / Chapter 3.4 --- Northern hybridization of hSP56 --- p.84 / Chapter 3.5 --- Cloning of hSP56 into pAED4 --- p.87 / Chapter 3.6 --- Expression of the hSP56 in E. coli --- p.89 / Chapter 3.7 --- Chromosomal mapping of the hSP56 gene --- p.92 / Chapter CHAPTER 4 --- DISCUSSION / Chapter 4.1 --- General discussion --- p.94 / Chapter 4.2 --- The possible roles of hSP56 and mSP56 --- p.101 / Chapter 4.3 --- Future prospects --- p.102 / REFERENCES --- p.103 / APPENDIX 1 --- p.125 / APPENDIX.2 --- p.127