No description available.

Yu, Wai Han. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 87-101). / Abstracts in English and Chinese. / ACKNOWLEDGEMENTS --- p.iii / ABSTRACT --- p.iv / 摘要 --- p.vi / LIST OF CONTENTS --- p.viii / LIST OF FIGURES --- p.xii / LIST OF TABLES --- p.xiv / LIST OF ABBREVIATIONS --- p.xv / Chapter CHAPTER 1. --- GENERAL INTRODUCTION --- p.1 / Chapter CHAPTER 2. --- LITERATURE REVIEW --- p.3 / Chapter 2.1 --- The importance of rice --- p.3 / Chapter 2.2 --- Limitation of essential amino acids in rice --- p.4 / Chapter 2.3 --- Lysine biosynthetic pathway --- p.6 / Chapter 2.3.1 --- The biosynthesis of aspartate --- p.6 / Chapter 2.3.2 --- Aspartate family pathway --- p.3 / Chapter 2.3.2.1 --- Aspartate kinase (AK) --- p.10 / Chapter 2.3.2.2 --- Dihydrodipicolinate synthase (DHPS) --- p.12 / Chapter 2.3.2.3 --- Other enzymes --- p.14 / Chapter 2.4 --- Regulation of lysine content in plant --- p.15 / Chapter 2.5 --- Enhancement of lysine content in plants --- p.16 / Chapter 2.5.1 --- "Breeding, selection and naturally occuring muatnts" --- p.17 / Chapter 2.5.2 --- Induced biochemical mutants --- p.18 / Chapter 2.5.3 --- Transgenic plants --- p.19 / Chapter 2.6 --- Hypothesis --- p.24 / Chapter CHAPTER 3. --- MATERIALS AND METHODS --- p.25 / Chapter 3.1 --- Introduction --- p.25 / Chapter 3.2 --- Chemicals --- p.25 / Chapter 3.3 --- Bacterial strains --- p.25 / Chapter 3.4 --- Cloning of AK and DHPS cDNAs --- p.25 / Chapter 3.4.1 --- Plant materials --- p.25 / Chapter 3.4.2 --- RNA extraction --- p.26 / Chapter 3.4.3 --- RT-PCR amplification of AK and DHPS cDNAs --- p.26 / Chapter 3.4.4 --- Sequence modification of AK and DHPS cDNAs --- p.27 / Chapter 3.4.5 --- DNA sequencing of AK and DHPS cDNAs --- p.32 / Chapter 3.5 --- Chimeric gene construction for rice transformation --- p.32 / Chapter 3.5.1 --- Plasmid and genetic material --- p.32 / Chapter 3.5.2 --- Construction of chimeric genes with seed-specific promoter --- p.35 / Chapter 3.5.3 --- Sequence fidelity of chimeric genes --- p.37 / Chapter 3.6 --- AEC resistance of E.coli expressing modified AK and DHPS --- p.37 / Chapter 3.7 --- Rice transformation --- p.38 / Chapter 3.7.1 --- Plant materials --- p.38 / Chapter 3.7.2 --- Preparation of agrobacterium --- p.33 / Chapter 3.7.3 --- Agrobacterium-mediated rice transformation --- p.39 / Chapter 3.7.3.1 --- Callus induction from mature rice seed embryos --- p.39 / Chapter 7.3.2 --- "Co-cultivation, selection and regeneration of transgenic rice" --- p.39 / Chapter 3.8 --- Analysis of transgenic expression --- p.41 / Chapter 3.8.1 --- Genomic DNA extraction --- p.41 / Chapter 3.8.2 --- Total RNA extraction --- p.41 / Chapter 3.8.3 --- Synthesis of DIG-labeled DNA probe --- p.42 / Chapter 3.8.4 --- Southern blot analysis --- p.43 / Chapter 3.8.5 --- Northern blot analysis --- p.43 / Chapter 3.8.6 --- Extraction of rice seed protein --- p.43 / Chapter 3.8.7 --- Tricine SDS-PAGE --- p.44 / Chapter 3.8.8 --- Raising AK and DHPS antibody --- p.44 / Chapter 3.8.9 --- Western blot analysis --- p.46 / Chapter 3.9 --- Free amino acid analysis --- p.46 / Chapter CHAPTER 4. --- RESULTS --- p.48 / Chapter 4.1 --- Cloning of AK and DHPS cDNAs from rice --- p.48 / Chapter 4.1.1 --- RNA extraction and cDNAs amplification --- p.43 / Chapter 4.1.2 --- Sequencing of AK and DHPS cDNAs --- p.50 / Chapter 4.2 --- Sequence modification of AK and DHPS cDNAs --- p.50 / Chapter 4.3 --- Construction of chimeric genes --- p.50 / Chapter 4.4 --- AEC resistance of E.coli expressing modified AK and DHPS --- p.56 / Chapter 4.5 --- Rice transformation --- p.58 / Chapter 4.6 --- Detection of target genes in transgenic rice lines --- p.60 / Chapter 4.6.1 --- PCR of genomic DNA --- p.60 / Chapter 4.6.2 --- Southern blot analysis --- p.63 / Chapter 4.7 --- Northern blot analysis --- p.65 / Chapter 4.8 --- Western blot analysis of AK and DHPS proteins --- p.66 / Chapter 4.9 --- Free amino acid analysis --- p.68 / Chapter 4.9.1 --- Free lysine content --- p.68 / Chapter 4.9.2 --- Changes in other amino acids --- p.69 / Chapter CHAPTER 5. --- DISCUSSION --- p.82 / Chapter 5.1 --- Cloning and modification of AK and DHPS cDNAs --- p.82 / Chapter 5.2 --- Seed-specific expression of modified AK and DHPS in rice --- p.82 / Chapter 5.3 --- Free amino acid changes in transgenic rice lines --- p.83 / Chapter 5.4 --- Future perspectives --- p.85 / Chapter CHAPTER 6. --- CONCLUSION --- p.86 / REFERENCES --- p.87 / APPENDIX --- p.102

Ionising radiation (IR) induces a wide spectrum of lesions in DNA, including double- and single-strand breaks, abasic (AP) sites and a variety of base lesions. IR-induced damage to DNA can range from simple, isolated lesions to clustered DNA damage in which multiple lesions are formed, usually within a single helical turn of the DNA. Individual lesions within a cluster are recognised by repair enzymes of the base excision repair (BER) pathway, however, clustered DNA damage may be recognised as a bulky lesion and be processed by nucleotide excision repair (NER). Additionally, the presence of other closely spaced lesions may affect the rate and fidelity of DNA repair and, in doing so, may contribute to the harmful effects of ionising radiation. The aim of this study is to gain further understanding of the repairability of clustered DNA damage and the effects of multiple lesions on cellular repair systems. 7, 8-dihydro-8-oxoguanine (8-oxoG), thymine glycol (Tg), AP sites and single-strand breaks (SSB), some of the most frequently formed IR-induced DNA lesions, were employed in synthetic oligonucleotides to model various types of clustered lesions and their repairability was studied using purified base excision repair enzymes and cell extracts. It was revealed that BER is the major repair system involved in the processing of clustered DNA lesions, and that some clustered lesions are repaired with decreased efficiency. Both the composition of lesions in a cluster and the positioning of the various lesions determine their repairability by base excision repair enzymes.

Brain glutamic acid decarboxylase 65 (GAD65) catalyzes the rate-limiting step in the biosynthesis of the major inhibitory neurotransmitter-amino butyric acid (GABA) from the substrate L-glutamic acid. Severe lapse in GABA neurotransmission is one of the etiologies documented in the manifestation of certain neurodegenerative diseases such as epilepsy, Parkinson's disease, Huntington's disease etc. Because GAD65 synthesizes GABA, any modulation of GAD65, therefore, has direct implications on the quanta of GABA released at the synapse. Hence, the major objective of this study was to focus on the regulation of GAD65, with special emphasis on investigating the proteolytic cleavage of fGAD65. Previously, we have shown in vitro that GAD65 was cleaved to form its truncated form (tGAD65), which was more active than the full length form (fGAD65). The enzyme responsible for cleavage was later identified as calpain. Calpain is known to cleave its substrates either under a transient physiologica l stimulus or upon a sustained pathological insult. However, the precise role of calpain cleavage of fGAD65 is poorly understood. In this study, we examined the cleavage of fGAD65 under a range of conditions encompassing both physiological and pathological aspects, including rats under ischemia/reperfusion insult, rat brain synaptosomes or primary neuronal cultures subjected to excitotoxic stimulation with KCl. It was observed that the formation of tGAD65 progressively increased with increasing stimulus concentration. More importantly, cleavage of synaptic vesicle (SV) - associated fGAD65 by calpain was demonstrated, and the resulting tGAD65 harboring the active site of the enzyme was detached from the SVs. Vesicular uptake of the newly synthesized GABA into the SVs was found to be reduced in calpain treated SVs. Furthermore, we also observed that the levels of tGAD65 in the focal cerebral ischemic rat brain tissue increased corresponding to the elevation of local glutamate indica / d by in vivo micro dialysis. Based on these observations, we conclude that calpain cleavage of fGAD65 occurs under pathological conditions. / by Chandana Buddhala. / Thesis (Ph.D.)--Florida Atlantic University, 2012. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2012. Mode of access: World Wide Web.

Huntington's disease (HD) is caused by an expanded plyglutamine repeat in the huntingtin protein. In this study, I focused on the effect of the mutant huntingtin protein (mhtt) on the subcellular localization of glutamic acid decarboxylase (GAD), the enzyme responsible for synthesizing gama-aminobutyric acid (GABA). Subcellular distribution of GAD65 is significantly altered in two neuronal cell lines that express either the N-terminus or full length mhtt. GAD65 is predominantly associated with the Golgi membrane in cells expressing normal huntingtin (Htt). However, it diffuses in the cytosol of cells expressing mhtt. Palmitoylation of GAD65 is required for GAD65 trafficking, and I demonstrated the palmitoylation of GAD65 is reduced in the HD model. Overexpression of huntingtin-interacting protein 14 (HIP14), the enzyme that palmitoylates GAD65, rescues GAD65 palmitoylation and vesicle-associated trafficking. This data suggests that impairment of GAD65 palmitoylation by mhtt may alter its localization and lead to altered inhibitory neurotransmission in HD. / by Daniel Rush. / Thesis (M.S.)--Florida Atlantic University, 2012. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2012. Mode of access: World Wide Web.

Indiana University-Purdue University Indianapolis (IUPUI) / Proteasome assembly is a rapid and highly sequential process that occurs through a series of intermediates. While the quest to understand the exact process of assembly is ongoing, there remains an incomplete understanding of what happens early on during the process, prior to the involvement of the β subunits. A significant feature of proteasome assembly is the property of proteasomal subunits to self-assemble. While archaeal α and β subunits from Thermoplasma acidophilum can assemble into entire 20S units in vitro, certain α subunits from divergent species have a property to self-assemble into single and double heptameric rings. In this study, we have shown that recombinant α subunits from Methanococcus maripaludis also have a tendency to self-assemble into higher order structures when expressed in E. coli. Using a novel cross-linking strategy, we were able to establish that these higher order structures were double α rings that are structurally similar to a half-proteasome (i.e. an α-β ring pair). Our experiments on M. maripaludis α subunits represent the first biochemical evidence for the orientation of rings in an α ring dimer. We also investigated self-assembly of α subunits in S. cerevisiae and attempted to characterize a highly stable and unique high molecular weight complex (HMWC) that is formed upon co-expression of α5, α6, α7 and α1 in E. coli. Using our cross-linking strategy, we were able to show that this complex is a double α ring in which, at the least, one α1 subunit is positioned across itself. We were also able to detect α1-α1 crosslinks in high molecular weight complexes that are formed when α7 and α1 are co-expressed, and when α6, α7 and α1 are co-expressed in E. coli. The fact that we able to observe α1-α1 crosslinks in higher order structures that form whenever α7 and α1 were present suggests that α1-α1 crosslinks might be able to serve as potential trackers to detect HMWCs in vivo. This would be an important step in determining if these HMWCs represent bona fide assembly intermediates, or dead-end complexes whose formation must be prevented in order to ensure efficient proteasome assembly.